Method and apparatus for neighbor cell measurement for cell reselection in wireless communication system

Abstract

A method for performing cell reselection by a user equipment (UE) based on a non-terrestrial network (NTN) in a wireless communication system is provided. Here, the method of performing cell reselection may include: acquiring cell reselection condition information from a base station; moving from a first cell to a second cell based on the mobility of the UE, and acquiring measurement-related information for cell reselection from the second cell; and performing an NTN cell search when a specific condition for cell reselection is satisfied based on the cell reselection condition information.

Description

Technical Field

[0001] The present invention relates to a method and device for neighboring cell measurement for cell reselection in a wireless communication system.

[0002] The present invention relates to a method for performing cell reselection based on a non-terrestrial network (NTN). Background Art

[0004] 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”.

[0005] 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.

[0006] In addition, in a new communication system, a method of supporting seamless communication services to user equipment (UE) (e.g., vehicle / train / ship-type terminals / personal smart phones) using not only a terrestrial network (TN) but also a non-terrestrial network (NTN) is being discussed, and a method of measuring neighboring cell reselection and performing cell reselection considering UE mobility between NTN and TN is described. Summary of the invention Technical Topics

[0008] The present invention may provide a method and apparatus for performing cell reselection in a wireless communication system.

[0009] The present invention relates to a method for performing cell reselection in a non-terrestrial network (NTN) environment.

[0010] The present invention relates to a method of determining specific conditions to perform NTN cell reselection in an NTN environment.

[0011] The present invention relates to a method of determining specific conditions to perform Terrestrial Network (TN) cell reselection in an NTN environment.

[0012] Technical Solution

[0013] According to an embodiment, a method for performing cell reselection based on a non-terrestrial network (NTN) by a user equipment (UE) in a wireless communication system may be provided. Here, the method for performing cell reselection may include: acquiring cell reselection condition information from a base station; moving from a first cell to a second cell based on the mobility of the UE, and acquiring measurement related information for cell reselection from the second cell; and performing NTN cell search when a specific condition for cell reselection is met based on the cell reselection condition information.

[0014] Furthermore, according to an embodiment, the cell reselection condition information may be configured based on at least one of a Tracking Area Code (TAC) list, a RAN Area Code (RAC) list, and a cell ID.

[0015] In addition, according to an embodiment, the cell reselection condition information may be sent to the UE via a radio resource control (RRC) message.

[0016] Furthermore, according to one embodiment,

[0017] A method for performing cell reselection based on a non-terrestrial network (NTN) by a user equipment (UE) in a wireless communication system, the method comprising: acquiring reference location information and distance threshold information about each cell in at least one cell from a base station; deriving distance condition information based on the reference location information and the distance threshold information about each cell in the at least one cell; and performing a TN cell search based on a current location of the UE and the distance condition information.

[0018] In addition, according to an embodiment, reference location information and distance threshold information about each of the at least one cell may be included in frequency information configured for each of the at least one cell.

[0019] Furthermore, according to one embodiment, the at least one cell may include a TN cell or an NTN cell.

[0020] 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.

[0021] Beneficial Effects

[0022] According to the present disclosure, a method and apparatus for performing cell reselection in a wireless communication system may be provided.

[0023] According to the present disclosure, a method for performing cell reselection in a non-terrestrial network (NTN) environment may be provided.

[0024] According to the present disclosure, a method for determining a specific condition for performing NTN cell reselection in an NTN environment may be provided.

[0025] According to the present disclosure, a method of determining a specific condition for performing a terrestrial network (TN) cell reselection in an NTN environment may be provided.

[0026] 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

[0028] Figure 1 An example of describing a New Radio (NR) frame structure to which the present disclosure is applicable is shown.

[0029] Figure 2 The NR resource structure to which the present disclosure is applicable is shown.

[0030] Figure 3 A non-terrestrial network (NTN) including transparent satellites to which the present disclosure can be applied is shown.

[0031] Figure 4 An NTN including a regenerative satellite without inter-satellite links (ISL) to which the present disclosure may be applied is shown.

[0032] Figure 5 An NTN including a regenerative satellite with an ISL to which the present disclosure may be applied is shown.

[0033] 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.

[0034] 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.

[0035] Figure 8 A timing advance calculation method to which the present disclosure can be applied is shown.

[0036] Fig. 9 A geostationary cell scenario to which the present disclosure can be applied is shown.

[0037] Fig.10 The figure shows an earth mobile cell scenario to which the present disclosure can be applied.

[0038] Fig.11A method of mapping a physical cell ID (PCI) to a satellite beam to which the present disclosure may be applied is shown.

[0039] Fig.12 A method of covering multiple tracking areas (TAs) by a satellite to which the present disclosure may be applied is shown.

[0040] Fig.13 A method for measuring TN cells in an NTN environment applicable to the present disclosure is shown.

[0041] Fig.14 An overlapping environment of TN cells and NTN cells applicable to the present disclosure is shown.

[0042] Fig.15 An environment where TN cells and NTN cells applicable to the present disclosure overlap is shown.

[0043] Fig.16 A method of performing measurement based on a Tracking Area Code (TAC) list to which the present disclosure may be applied is shown.

[0044] Fig.17 The NTN cell measurement signaling process based on the TAC list applicable to the present disclosure is shown.

[0045] Fig.18 A method for performing a cell list-based measurement process applicable to the present disclosure is shown.

[0046] Fig.19 The NTN cell measurement signaling process based on the cell list applicable to the present disclosure is shown.

[0047] Fig.19 A new timer to which the present disclosure can be applied is shown.

[0048] Fig. 20 A method for performing measurements based on a RAN Area Code (RAC) applicable to the present disclosure is shown.

[0049] Fig.21 A method for performing measurements based on RAC applicable to the present disclosure is shown.

[0050] Fig. 22 The NTN cell measurement signaling process based on the RAC list applicable to the present disclosure is shown.

[0051] Fig.23 A method of performing measurement based on at least one of a TAC, a cell, and a RAC list applicable to the present disclosure is shown.

[0052] Fig.24 An NTN cell measurement signaling procedure based on at least one of a TAC, a cell, and a RAC list applicable to the present disclosure is shown.

[0053] Fig.25 A synchronization signal block (SSB) configuration suitable for use with the present disclosure is shown.

[0054] Fig.26 An SSB-based Measurement Timing Configuration (SMTC) window configuration configured in a network for measuring a specific frequency applicable to the present disclosure is shown.

[0055] Fig. 27 A method for performing a cell search based on neighboring TN cell reference positions applicable to the present disclosure is shown.

[0056] Fig.28 A TN cell configuration suitable for the present disclosure is shown. As described above, information about TN neighbor cells and information for cell reselection may be related.

[0057] Fig.29 NTN cell reference locations suitable for use in the present disclosure are shown.

[0058] Fig.30 is a flow chart illustrating a method of performing a conditional NTN cell search applicable to the present disclosure.

[0059] Fig.31 is a flow chart illustrating a method of performing a conditional TN cell search applicable to the present disclosure.

[0060] Fig.32 is a diagram showing a device configuration to which the present disclosure can be applied. DETAILED DESCRIPTION

[0062] 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.

[0063] 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.

[0064] 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.

[0065] 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.

[0066] 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.

[0067] 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.

[0068] 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.

[0069] 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).

[0070] 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.

[0071] 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.

[0072] 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).

[0073] 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.

[0074] First, the physical resource structure of the NR system to which the present disclosure is applied will be briefly described.

[0075] Figure 1 An example of an NR frame structure according to an example of the present invention is shown.

[0076] 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, k = 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.

[0077] 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.

[0078] 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.

[0079] [Equation 1]

[0080] T TA =(N TA +N TA,offset )T c

[0081] 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.

[0082] Figure 2 An NR resource structure to which the present disclosure is applicable is shown.

[0083] 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.

[0084] 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.

[0085] [Equation 2]

[0086]

[0088] 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.

[0089] 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.

[0090] Table 1 below shows an example of digital parameters supported by the NR system.

[0091] [Table 1]

[0092]

[0093] 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.

[0094] 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.

[0095] 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.

[0096] 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).

[0097] 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.

[0098] 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).

[0099] [Table 2]

[0100]

[0101] 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.

[0102] [Table 3]

[0103]

[0104] 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.

[0105] 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.

[0106] [Table 4]

[0107] 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

[0109] 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.

[0110] 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.

[0111] In the following, a terrestrial network (TN) is described distinguishably from a non-terrestrial network (NTN). That is, in an existing communication system, only a 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.

[0112] 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.

[0113] 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.

[0115] Non-terrestrial network (NTN):

[0116] 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.

[0118] NTN Gateway:

[0119] 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).

[0121] Feederlink:

[0122] It is the radio link between the NTN gateway and the satellite.

[0124] Geosynchronous Orbit (GEO):

[0125] 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.

[0127] Low Earth Orbit (LEO):

[0128] It is an orbit between 300km and 1500km above the Earth.

[0130] Medium Earth Orbit (MEO):

[0131] It is an orbit between LEO and GEO.

[0133] Unmanned Aerial Systems (UAS):

[0134] 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.

[0136] Minimum elevation angle:

[0137] It is the minimum angle required for a land terminal to face a satellite or UAS base station in the sky.

[0139] Mobile Services:

[0140] They are wireless communication services between terrestrial base stations and wireless terminals or between mobile base stations.

[0142] Mobile Satellite Services:

[0143] 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.

[0145] Non-geosynchronous satellites:

[0146] 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.

[0148] Onboard processing:

[0149] It is the digital processing of uplink radio frequency (RF) signals mounted on satellites or non-terrestrial equipment.

[0151] Transparent Payload :

[0152] This may mean changing the carrier frequency of the uplink RF signal and filtering and amplifying it before sending it over the downlink.

[0154] Regeneration Payload:

[0155] 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.

[0157] Airborne NTN base station (gNB):

[0158] It can mean an onboard satellite where the base station (gNB) is implemented in a regenerative payload structure.

[0160] NTN base station on the ground (gNB):

[0161] It is a terrestrial base station in which the base station (gNB) is implemented with a transparent payload structure.

[0163] One-way waiting time:

[0164] 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.

[0166] Round Trip Delay (RTD):

[0167] 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.

[0169] satellite:

[0170] 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.

[0172] Satellite beam:

[0173] It is a beam generated by the antenna onboard the satellite.

[0175] Service link:

[0176] It is the radio link between the satellite and the UE.

[0178] User Connectivity:

[0179] It is capable of configuring and maintaining data / voice / video transmission between the network and the UE.

[0181] User throughput:

[0182] It is the data transmission rate provided to the UE.

[0184] Figure 3 An NTN including transparent satellites to which the present disclosure can be applied is shown.

[0185] 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.

[0186] 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.

[0187] 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.

[0188] Figure 4An NTN including regenerative satellites without inter-satellite links (ISLs) to which the present disclosure may be applied is shown.

[0189] 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.

[0190] 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.

[0191] Figure 5 An NTN including a regenerative satellite with an ISL to which the present disclosure may be applied is shown.

[0192] 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.

[0193] 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.

[0194] 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.

[0195] 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.

[0196] 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.

[0197] 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.

[0198] 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.

[0199] 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.

[0200] Here, for initial access and continuous maintenance of a timing advance (TA) value, a case where the UE knows the satellite ephemeris and the location of the UE may be considered. Here, the satellite ephemeris may indicate the distance between each satellite and the receiver and the location information of each satellite. For example, the UE may obtain the 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).

[0201] 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.

[0202] Through the above description, the UE may perform UE-to-UE uplink timing alignment received from the base station as full TA compensation.

[0203] 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.

[0204] 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.

[0205] Fig. 9 A geostationary cell scenario to which the present disclosure can be applied is shown.

[0206] 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.

[0207] 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.

[0208] 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.

[0209] 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.

[0210] also, Fig.11 A method of mapping PCIs to satellite beams to which the present disclosure may be applied is shown.

[0211] 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.

[0212] 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.

[0213] As described above, the UE can perform communication through the NTN. For example, the UE can receive services based on 5G / B5G NTN. 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.

[0214] 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.

[0215] 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.

[0216] 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.

[0217] 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.

[0218] 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.

[0219] 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.

[0220] 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.

[0221] 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.

[0222] Fig.12 The present disclosure is applicable to a method for covering multiple tracking areas (TAs) by satellites. The UE may be registered with the network through a registration process. The UE registered with the network (e.g., 5G MM-REGISTERED) may send a registration request message to an access and mobility management function (AMF) for periodic registration updates according to mobility.

[0223] In detail, when the tracking area identifier (TAI) of the UE is not currently in the tracking area list received from the previously registered AMF (i.e., when the UE moves to a tracking area code (TAC) that does not exist in the previously registered registration area), the UE may send a registration request message to the AMF for mobility registration update. Here, TAI may represent an identifier that includes a public land mobile network (PLMN) (MCC+MNC) and a TAC. As another example, when the UE receives a configuration update command, the UE may send a registration request message to the AMF for mobility registration update. As another example, when the UE requests new local area data network (LADN) information, the UE may send a registration request message to the AMF for mobility registration update. Here, when a specific service is provided only in a specific area, the local area data network (LADN) may represent the corresponding area. For example, the UE may perform a data network connection through a protocol data unit (PDU) session only in a specific TA representing the geographical information of the corresponding area.

[0224] As another example, when a periodic registration update process occurs due to expiration of a timer (e.g., T3512) in a UE in an RRC idle state, the UE may transmit a registration request message to the AMF for mobility registration update. That is, the UE may perform mobility registration update based on various conditions and may not be limited to the above-mentioned cases.

[0225] Reference Fig.12 , a case where the UE performs communication based on NTN can be considered. As described above, the NTN satellite 1210 can be connected to the base station (gNB) 1230 through the NTN gateway 1220. For example, the NTN satellite 1210 can serve a wider coverage area than the TN. Therefore, the NTN satellite 1210 can cover multiple TAs. As a detailed example, based on NTN communication, the NTN cell (e.g., satellite NG-RAN) can have a TAC corresponding to an area served by the satellite (e.g., TA 1, TA 2, TA 3, TA, ..., TA 58, TA 59, TA 60). Here, the NTN cell can broadcast multiple TACs for the area served by the NTN cell through system information. When the UE receives information about the multiple TACs through the system information, a single TAI can be selected in the non-access stratum (NAS) layer of the UE. Here, the TAI may include a PLMN and a TAC.

[0226] When the UE resides in the NTN cell, the UE may receive the multiple TACs from the lower layer. The UE may configure multiple TAIs through the multiple TACs and the current PLMN. The UE may select a single TAI from the configured multiple TAIs. In detail, when only a single TAI is included in the current registration area of ​​the UE, the UE may select the TAI. On the other hand, when multiple TAIs are included in the current registration area of ​​the UE, the UE may select the TAI based on the tracking area information included in the service area information. Here, the tracking area information may include allowed tracking area information and not allowed tracking area information. The UE may select a TAI that includes an allowed tracking area but does not include an not allowed tracking area. For example, when multiple TAIs are included in an allowed tracking area but not included in an not allowed tracking area, the UE may select a single TAI according to a pre-configured method (e.g., LADN service area information). That is, the UE may select a single TAI from multiple TAIs configured in the UE based on specific conditions.

[0227] On the other hand, when all TAIs are not included in the current registration area of ​​the UE, the UE may select a TAI that is not included in the network access prohibited TAI list (e.g., 5GS prohibited tracking area for roaming, 5GS prohibited tracking area for providing services). In addition, for example, when there are multiple TAIs, the UE may select a single TAI from the multiple TAIs based on specific conditions. The UE may consider the selected TAI as the current TAI.

[0228] Here, the case where the lower layer of the UE sends the multiple TACs to the NAS layer can be considered. Here, the UE can perform the TAI selection operation based on one of the following situations: the case where the tracking area information (e.g., allowed tracking area, not allowed tracking area) changes, and the case where the network prohibited information (e.g., 5GS prohibited tracking area for roaming, 5GS prohibited tracking area for providing services) changes.

[0229] Hereinafter, a method for measuring neighbor cells by a UE for cell reselection in an NTN system is described.

[0230] For example, in a wireless communication system (e.g., 3GPP NR), a frequency band for NTN communication may be defined as a frequency band FR1 (450 MHz to 6 GHz), FR2 (24.25 GHz to 52.6 GHz), FR2x (52.6 GHz to 71 GHz), FR3 (7.125 GHz to 24.25 GHz), and FR4 (52.6 GHz to 114.25 GHz). Here, at least one of uplink, downlink, bandwidth, and duplex mode may be indicated by a plurality of operating frequency bands within the corresponding frequency band. For example, in the NTN system, an S band region of 1980 to 2010 MHz and 2170 to 2200 MHz may be used. The corresponding frequency band may overlap with a frequency band of an existing wireless communication system (e.g., 3GPP NR).

[0231] As a detailed example, in FR1, if bands 1 and 65 of a wireless communication system (eg, 3GPP NR) use a frequency domain adjacent to or the same as an NTN band, a cross-border problem may occur.

[0232] Referring to Table 5, the NTN operating band may overlap with the TN band. For example, the NTN band may completely overlap with the TN band (uplink operating band 1920 to 2010 MHz, downlink operating band 2110 to 2200 MHz) in band 65 as FDD operation. In addition, the NTN operating band may partially overlap with the TN band (uplink operating band 1626.5 to 1660.5 MHz, downlink operating band 1525 to 1559 MHz) in band 24 as frequency division duplex (FDD) operation. Therefore, operators may need to coordinate the use of bands for TN and NTN in the same geographical location.

[0233] [Table 5]

[0234]

[0236] Furthermore, for example, in order to perform neighbor cell measurements for cell reselection, the UE may consider the following information.

[0238] Public Land Mobile Network (PLMN) Selection

[0239] The UE can verify the available RF band based on its ability to search for available PLMNs and closed access groups (CAGs) within the NR band. The UE can search for the cell with the strongest signal strength and can verify system information to determine which PLMNs are included in each carrier and which CAGs are involved.

[0241] Cell reselection and measurement information

[0242] For example, system information block 2 (SIB2) may include common information about intra-frequency / inter-frequency and inter-RAT for cell reselection of UE. Such intra-frequency / inter-frequency and inter-RAT information for cell reselection may include at least one of the following parameters: about the number of SSBs for measuring the average value of signal strength as signal strength (nrofSS-BlocksToaverage), SSB signal strength threshold (absThreshSS-BlocksConsolidation), the range of cell ranking criteria R for final cell reselection (rangeToBestCell), scaling factor (Q-Hyst), and mobility state parameters (MobilityStateParameters) for estimating the movement / speed state of the UE. In addition, SIB2 may include at least one of the following: general information (cellReselectionServingFreqInfo) for inter-frequency (inter-frequencync) and inter-RAT (inter-RAT) reselection, signal strength threshold (s-NonIntraSearchP) for measurement triggering, signal quality threshold (s-NonIntraSearchQ), signal strength threshold (threshServingLowP) for cell reselection to the same or lower priority inter-frequency, inter-RAT, signal quality threshold (threshServingLowQ) and priority (cellReselectionPriority, cellReselectionSubPriority). In addition, SIB2 may include at least one of the following: information for intra-frequency cell reselection (intraFreqCellReselectionInfo), minimum signal strength (q-RxLevMin, q-RxLevMinSUL) for calculating the signal strength of adjacent intra-frequency cells during the cell selection standard (S standard) process, minimum signal quality (q-QualMin), signal strength threshold for measurement triggering (s-IntraSearchP), signal quality threshold (s-IntraSearchQ), time for reselection (t-ReselectionNR), frequency band list for applying cell reselection parameters (frequencyBandList), SSB-based measurement timing configuration (SMTC), and SSB to be measured within the SMTC duration (SSB-ToMeasure).

[0244] Frequency measurement process

[0245] For example, SIB4 includes information of neighboring cells associated with inter-frequency cell reselection. The above information relates to cell reselection parameters for a single frequency and can be applied as cell-specific information only within a specific cell. In addition, for example, SIB4 includes an inter-frequency information list (interFreqCarrierFreqList) and can include information about up to eight frequencies.

[0246] In each piece of frequency information, the downlink carrier frequency can be indicated by an absolute radio frequency channel number (ARFCN) (dl-CarrierFreq) value. In the case of including multiple frequency bands, SIB4 may include: a frequency band list (FrequencyBandList), a parameter about the number of SSBs used to measure the signal strength average as the signal strength (nrofSS-BlocksToaverage), an SSB signal strength threshold (absThreshSS-BlocksConsolidation), SMTC, SSB subcarrier spacing (ssbSubcarrierSpacing), SSBs to be measured within the SMTC duration (ssb-ToMeasure), an indication of whether to derive the SSB index of the neighboring cell from the serving cell (deriveSSB-IndexFromCell), an indication of a specific time slot for measuring the signal strength of the SSB within the SMTC window, and symbol information (ss-RSSI-Measurement), minimum signal strength for signal strength calculation of adjacent frequency cells in the cell selection criterion (S standard) process (q-RxLevMin, q-RxLevMinSUL), minimum signal quality (q-QualMin), reselection time (t-ReselectionNR), signal strength threshold for cell reselection to frequency according to priority (threshX-HighP, threshX-LowP), signal quality threshold (threshX-HighQ, threshX-LowQ), priority (cellReselectionPriority, cellReselectionSubPriority), signal strength offset according to frequency used in the cell R standard ranking procedure (cell R-criterion ranking procedure) (q-OffsetFreq), adjacent cell information list (InterFreqNeighCellList) and excluded adjacent cell information list (interFreqExcludedCellList). Here, the neighboring cell information list may include at least one of the following: at least one PCI (physCellId), a signal strength offset (q-OffsetCell) used in the cell R standard sorting process, a minimum signal strength (q-RxLevMinOffsetCell) used for signal strength calculation in the cell selection S standard process, and minimum signal quality (q-QualMinOffsetCell) information.In addition, in the neighbor cell information list, the allowed cell list (intraFreqAllowedCellList) and the excluded cell list (ntraFreqExcludedCellList) can be specified as a PCI range. Here, the PCI range can be indicated by a starting PCI and a range (4, 8, 12, 16, ..., 1008).

[0248] Intra-frequency measurement process

[0249] SIB3 includes information of neighboring cells associated with intra-frequency cell reselection. The neighboring cell information list (IntraFreqNeighCellList) may include at least one of the following: at least one PCI (physCellId), a signal strength offset (q-OffsetCell) used in the cell R standard ranking process, the minimum signal quality (q-(q-RxLevMinOffsetCell) and minimum signal quality (q-QualMinOffsetCell) information used for signal strength calculation in the cell selection S standard process. In addition, in the neighboring cell information list, the allowed cell list (intraFreqAllowedCellList) and the excluded cell list (intraFreqExcludedCellList) may be indicated as PCI ranges. Here, the PCI range may be indicated by a starting PCI and a range (4, 8, 12, 16, …, 1008).

[0251] Measurement rules for cell reselection

[0252] In an existing wireless communication system (e.g., NR), if the signal strength of the serving cell is greater than or equal to a threshold, the RRC idle / inactive UE may not perform inter-frequency measurements. On the contrary, if the signal strength of the serving cell is less than the threshold, the RRC idle / inactive UE may always perform inter-frequency measurements. In addition, for example, the UE may always measure an inter-frequency with a higher priority than the current NR frequency. On the other hand, in the case of a priority equal to or less than the current NR frequency, if the signal strength of the serving cell is greater than or equal to a specific threshold, the UE may not perform inter-frequency measurements, and if the signal strength of the serving cell is less than the threshold, the UE may perform inter-frequency measurements.

[0254] SMTC (SSB-based Measurement Timing Configuration)

[0255] For example, in existing wireless communication systems (e.g., LTE), by periodically sending a cell-specific reference signal (CRS), the UE is able to measure the signal strength of the serving / neighboring cell. However, in current wireless communication systems (e.g., NR), the concept of Always-on-Signal (e.g., CRS) may not be applied to reduce overhead and interference from neighboring cells. Therefore, in current wireless communication systems, the UE needs to measure the signal strength (RSRP, RSRQ) of the serving cell and the neighboring cell in order to switch to a cell with stronger signal strength or add a new carrier. Therefore, in current wireless communication systems (e.g., NR), the UE can measure the signal strength through a synchronization signal (SS) / PBCH block (SSB), which includes an SS and a physical broadcast channel (PBCH) for downlink synchronization.

[0256] In detail, the number of SSBs may vary depending on the frequency operating band. For example, in FR1 of 3 GHz or less, four SSBs may be configured in a single burst. Moreover, in FR1 of 3 to 6 GHz, eight SSBs may be configured in a single burst. Moreover, in a frequency band of 6 GHz or greater, 64 SSBs may be configured in a single burst. SSB burst sets may be periodically sent from a cell with a period of 5, 10, 20, 40, 80, or 160 ms, but the signal strength does not need to be measured in each SSB period to reduce the power consumption of the UE. For example, an SMTC window may be applied so that the UE can perform SSB measurements and can verify the signal strength. That is, the UE can reduce the power consumption of the UE by periodically measuring the signal strength of the SSB for each SMTC window.

[0257] Here, the network can configure the SMTC window in the UE through an RRC message. In detail, the network can send ssbFrequency (NR-ARFCN), SSB SCS (ssbSubcarrierSpacing) and SMTC information in MeasObjectNR through an RRC message. The network can configure the duration of the period (periodicity) and offset information (PeriodicityAndOffset) and the window size in time units in SMTC through an RRC message. As another example, the network can provide specific frequency information (ARFCN) and SMTC information to the UE together in the system information. The UE can determine which frequency band to verify at which point in time through the frequency information (ARFCN) and time information (SMTC).

[0258] For example, in an NTN environment with large propagation delay, since it is impossible to include all multiple cells within the SMTC window, multiple SMTCs may be configured. In addition, even in an RRC connected / inactive / idle environment, the UE can perform signal strength measurements for the serving cell and the neighboring cells. In the following, a method for measuring neighboring cells for cell reselection by the UE is described based on the above.

[0259] In NTN-TN and NTN-NTN, a technology for providing service continuity in consideration of mobility may be required. For example, a method for performing measurements and providing service continuity based on mobility between NTN and TN and between NTN and NTN may be required.

[0260] In more detail, a method for reducing power consumption of RRC idle / inactive UEs is described below. For example, the UE may operate based on one of an RRC connected state, an RRC idle state, and an RRC inactive state. Here, if the RRC of the UE is logically connected to the RRC of the core network, it may be an RRC connected state. On the contrary, if the RRC of the UE is not connected to the RRC of the core network, it may be an RRC idle state. However, a large amount of signaling will inevitably occur when entering the RRC connected state from the RRC idle state. In view of the above, an RRC inactive state may exist. In the case of the RRC inactive state, the UE may be considered to be in a connected state from the perspective of the core network. That is, the core network may maintain both the user plane and the control plane of the UE in an active state. Therefore, in the RRC inactive state, paging may be initiated by the RAN.

[0261] In the following, a method for reducing the power consumption of a UE is described. In particular, a UE in an RRC idle / inactive state is not in a state of sending data, and therefore its power consumption needs to be minimized. Here, in an existing wireless communication system (e.g., Rel-17), the UE may preferentially select / reside on a TN cell in a relationship between an NTN and a TN cell. Therefore, the UE needs to seamlessly measure the signal strength of the surrounding TN cells, which may result in constant power consumption. Below, a method for performing a conditional cell search in consideration of the above situation is described.

[0262] Fig.13 The method for measuring TN cells in an NTN environment applicable to the present disclosure is shown. Fig.13, the NTN cell coverage can be determined based on the NTN satellite 1310. Here, the TN cell may exist within the NTN cell coverage. In detail, for UE 1 1321, UE 2 1322, and UE 3 1323, there may not be a TN cell with sufficient signal strength. Therefore, UE 1 1321, UE 2 1322, and UE 3 1323 are camping on the NTN cell, and a cell search for the TN frequency domain may be performed all the time to camp on the TN cell. On the other hand, for UE 4 1324, UE5 1325, UE 6 1326, and UE 7 1327, which are UEs within the NTN cell coverage, there may be a TN cell with sufficient signal strength. Therefore, UE 4 1324, UE5 1325, UE 6 1326, and UE 7 1327 may camp on the TN cell. Here, UE 1 1321, UE 2 1322, and UE 3 1323 camping on the NTN cell are camping on the NTN cell, but will search for the TN cell by performing measurements of the TN cell, which may result in increased power consumption. Therefore, a method of reducing power consumption is needed.

[0263] Furthermore, even UE 4 1324, UE 5 1325, UE 6 1326, and UE 7 1327 camping on the TN cell constantly perform measurements of the NTN cell, which may result in power consumption. Therefore, a method of reducing power consumption is needed.

[0264] Below, each of the method (method 1) of performing conditional NTN cell search (frequency measurement) and the method (method 2) of performing conditional TN cell search (frequency measurement) is described based on the above content. Here, method 1 and method 2 may not be mutually exclusive because they are contradictory. Although each method is described separately for clarity of description, it can be understood that each method is applicable according to the situation of the UE.

[0266] Method 1 (Conditional NTN cell search (frequency measurement))

[0267] The UE may perform measurements for cell reselection of inter-frequency and inter-RAT frequencies indicated by system information. Here, the conditions for performing measurements for cell reselection of inter-frequency and inter-RAT frequencies may be as shown in Table 6 below. That is, the UE may determine whether to perform measurements based on whether the priority of the inter-frequency or inter-RAT frequency is higher than the priority of the current frequency and whether the signal strength and signal quality of the serving cell are greater than a threshold. Specifically, the case where the priority of the inter-frequency or inter-RAT frequency is lower than the priority of the current frequency, but the signal strength and signal quality of the serving cell are greater than the threshold may be considered. Here, if the distance between the UE and the reference location is less than the distance threshold set based on the system information, the UE may not perform measurements for the inter-frequency or inter-RAT frequency. If the distance between the UE and the reference location is greater than the distance threshold, the UE may perform measurements for the inter-frequency or inter-RAT frequency. On the other hand, if there is no distance threshold set based on the system information, the UE may not always perform measurements for the inter-frequency or inter-RAT frequency.

[0268] In addition, when the priority of the inter-frequency or inter-RAT frequency is lower than the priority of the current frequency, but the signal strength and signal quality of the serving cell are lower than the threshold, the UE can perform inter-frequency or inter-RAT frequency measurement.

[0269] In addition, for example, when there is a t-service of the serving cell in the system information (e.g., SIB19), the UE may perform intra-frequency / inter-frequency and inter-RAT frequency measurements before the t-service, regardless of the conditions shown in Table 6 below. Here, t-service may refer to the epoch time when the fixed cell provides coverage. As another example, the UE may perform measurements on high priority intra-frequency / inter-frequency and inter-RAT frequencies, regardless of the conditions shown in Table 6.

[0270] [Table 6]

[0271]

[0273] Fig.14 The overlapping environment of TN cells and NTN cells applicable to the present disclosure is shown. Fig.14 , the NTN cell A based on satellite 1410 can overlap with the TN cell. Here, Fig.14 The coverage of NTN cell A shown in (b) can be compared Fig.14 The coverage of NTN cell A shown in (a) is wider, however, for the sake of clarity of description, this is only an example. Multiple cells may exist in an area served by a satellite and are not limited to a specific embodiment.

[0274] For example, Fig.14 The coverage of the NTN cell shown in (a) and (b) can be an urban area where TN cells are densely present and a suburban / mountainous area where TN cells are sparse or non-existent. As another example, Fig.14 (a) and (b) may be land areas where TN cells are densely present and ocean areas where TN cells are sparse or non-existent, but may not be limited to a specific implementation scheme. Here, a registration area (RA) may be an area that a network may configure in consideration of the mobility and service of a UE. The RA may be configured in a UE through multiple TACs. Thus, a UE may move and reside on a TN or NTN cell without requiring a registration update procedure within the RA.

[0275] Here, for example, Fig.14 In (a) and (b), the UE may camp on a TN cell and may be present at the edge of coverage (TN cell edge), where the signal strength or signal quality of the TN cell (serving cell) is less than a specific value. Here, the UE may perform an NTN cell measurement and search procedure. However, in the case where there are many neighboring TN cells around the UE, the UE needs to camp on a TN cell instead of an NTN cell. Therefore, the NTN cell measurement and search procedure in the UE may be unnecessary.

[0276] As a more detailed example, in Fig.14 In (a) and (b), the UEs at the cell edge within TN cells 2 and 3 need to camp on the adjacent TN cells first. Therefore, NTN cell measurement and search may be unnecessary processes for UEs at the cell edge. Fig.14 As shown in (a), even in an area where there is no service coverage of NTN cell A, the UE may not need to perform NTN cell measurement and search procedures. Fig.14 As shown in (b), the service of NTN cell A covers the area where TN cells are densely populated, but the UE needs to stay in the TN cell first, so the measurement and search of the NTN cell may be unnecessary. On the other hand, since there are no adjacent TN cells, the UE staying on TN cell 6 may need NTN cell measurement and search, and may need to consider the cell search conditions of the above situation.

[0277] Fig.15 The figure shows an environment where TN cells and NTN cells overlap, which is applicable to the present disclosure. Fig.15 , NTN cell and TN cell can overlap based on satellite 1510.

[0278] Here, when the UE camps on a TN cell, the TN frequency can be configured to have a high priority, and the NTN frequency can be configured to have a low priority. That is, since the TN cell provides a high quality of service (QoS), the UE can be configured to preferentially camp on the TN cell. Here, if the signal strength (Srxlev) and signal quality (Squal) of the TN cell and the serving cell are less than the signal strength threshold (s-IntraSearchP) and the signal quality threshold, the UE can always measure the low priority inter-frequency or inter-RAT frequency, which can be shown in Table 6.

[0279] For example, if the UE is present at the cell edge, the signal strength and signal quality of the serving cell may be less than the signal strength threshold and signal quality threshold. In the above case, when the signal strength and signal quality of the serving cell of the UE camping on the TN cell become weak, the UE may basically be able to perform low priority NTN cell measurement. Fig.15 , NTN cell A can be Fig.15 (b) is better than Fig.15 (a) of FIG. 1 , however, this is merely an example for clarity of description, and multiple cells may exist in an area where a satellite can provide service. Fig.15 In (a) and (b), the TAC in the area where TN cells are densely populated or exist may be TAC 10 to TAC 26. For example, Fig.15 (a) and (b) of FIG. 5 can be an urban area where TN cells are densely present and a suburban / mountainous area where TN cells are sparse or non-existent. As another example, Fig.15 (a) and (b) may be land areas where TN cells are densely present and ocean areas where TN cells are sparse or non-existent, but may not be limited to a specific implementation scheme. Here, the UE may perform initial access through the TN cell and may receive a configuration about a registration area (RA) from the AMF. The RA is an area that the network may configure in consideration of the mobility and service of the UE and may be configured in the UE through multiple TACs. Therefore, the UE may move and reside on a TN cell or an NTN cell without requiring a registration update procedure within the RA.

[0280] Here, for example, reference Fig.15 In (a) and (b), the case where the UE resides on a TN cell with TAC 21 and the signal strength or signal quality of the TN cell (serving cell) is less than a specific value can be considered. In the above case, the UE can perform the NTN cell measurement and search process. However, in the case where there are many neighboring TN cells around the UE, the UE may not have to perform the NTN cell measurement and search process. In addition, for example, Fig.15As shown in (a) of FIG. 1 , even in an area without service coverage of NTN cell A, it may not be necessary to perform NTN cell measurement and search procedures. Fig.15 As shown in (b), although the service of NTN cell A covers the area where TN cells are densely present, the UE needs to camp on the high-priority TN cell, so NTN cell measurement and search may be unnecessary.

[0281] That is, as described above, if a UE that does not require NTN frequency measurement performs NTN frequency measurement, the UE may continuously consume power, and therefore, a method for reducing such consumption may be required. To this end, based on information (e.g., TAC / cell / RAC) that can estimate the location of the UE or a specific location, the UE camped on the TN cell can conditionally perform NTN cell measurement and search.

[0282] In detail, Fig.16 A method for performing measurements based on a Tracking Area Code (TAC) list applicable to the present disclosure is shown. Fig.16 , the coverage of NTN cell A can be determined based on satellite 1610. Here, UE 1620 in RRC idle state can perform initial access and then be assigned a registration area (RA) from AMF. RA refers to an area in which UE 1620 can move without performing registration update, and can include multiple TACs. As a detailed example, when UE 1620 is assigned a RA with TAC A, B and C, UE 1620 in RRC idle state can move to a cell with TAC A, B and C without performing a registration update procedure from AMF. On the other hand, if UE 1620 moves to a cell with TACD, UE 1620 can perform a registration update procedure to AMF and then be assigned a new RA.

[0283] Here, refer to Fig.16 , when the NTN cell and the TN cell overlap, the TAC may be configured based on the NTN cell and the TN cell. TAC may refer to a geographically fixed location. The cell of each base station may have a specific TAC identifier. As a detailed example, the AMF may assign a TAC identifier to the UE 1620 including Fig.16RA of all TACs (TAC 3 to TAC 25) shown. However, this is merely an example for clear description and is not limited to the above embodiments. UE 1620 can move within the RA without performing the registration update process to the AMF, and can reside on a cell with a single TAC within the RA. For example, when UE 1620 is present in the TAC 21 area, UE 1620 can reside on a TN cell with TAC 21. Here, when the UE moves to TAC 7, the UE can perform a residency to the NTN cell because there is no TN cell with a sufficiently strong signal strength. Here, NTN cell A may serve a wider area than the TN cell. Therefore, the NTN cell may send multiple TACs to UE 1620 through system information. The UE can derive the TAI by selecting a single TAC belonging to the RA from the multiple TACs obtained through the system information.

[0284] Here, the UE in the RRC idle state can receive the configuration of the cell reselection parameters for camping through an RRC message (e.g., RRC release, SIB2, 3, 4). That is, when UE 1620 shifts to the RRC idle state and then receives the configuration of the cell reselection parameters for the NTN cell at the TAC 21 position, the UE can continuously search for the NTN cell within the RA. Since the NTN cell exists within the RA, the network can configure the cell reselection parameters of the NTN cell using RRC messages. However, since UE 1620 cannot camp on an NTN cell in an area outside of TAC 4 to TAC 11 served by NTN cell A, performing a cell search may increase unnecessary power consumption.

[0285] In addition, since the TN cell supports a higher QoS than the NTN cell, for the UE 1620 camping on the TN cell, camping on the NTN cell through cell reselection may be an unnecessary process. On the other hand, in an area where the signal strength of the serving cell is insufficient and the SSB of the NTN cell can be received, the UE 1620 camping on the TN cell may need an NTN cell search. Specifically, if the signal strength is insufficient at the cell edge, the UE 1610 camping on the TN cell with TAC 10 may need to perform a cell search for NTN cell A. Considering the above situation, the UE 1610 can reduce power consumption by searching for NTN cells in a specific TAC.

[0286] Here, refer to Fig.16, the network may include TAC 4 to TAC 10 for NTN cell search served by NTN cell A and a TAC capable of detecting the SSB of NTN cell A in the TAC list. Here, the network may set the cell reselection parameter, and the parameter may be configured in UE 1620 through an RRC message. For example, UE 1620 present in TAC 21 may receive the configuration of the NTN cell reselection parameter and the TAC list through an RRC message (e.g., system information, RRC release) in the TN cell. UE 1620 may recognize that TAC 21 is a TAC that does not exist in the TAC list. Therefore, UE 1620 may perform only a TN cell search without performing an NTN cell search. In addition, in the case of moving to TAC 22 according to UE mobility, since UE 1620 only performs a search for a TN cell, UE 1620 may reside on a TN cell with TAC 22. On the other hand, in the case of moving to a TAC area (e.g., TAC 10) indicated by the TAC list according to UE mobility and camping on a TN cell with TAC 10, the UE 1620 may perform an NTN cell search based on the configured NTN cell reselection parameters. In addition, although the UE 1620 moves to the TAC area indicated by the TAC list, since the TN cell supports a higher QoS, the UE 1620 needs to prioritize the TN cell. Therefore, the UE 1620 camping on the TN cell needs to perform an NTN cell search in consideration of the process of verifying the signal strength of the serving cell and the TAC list.

[0287] Fig.17 FIG. 4 shows a TAC list-based NTN cell measurement signaling process applicable to the present disclosure. Fig.17, UE 1710 may receive an RRC message from TN cell A 1720 in an RRC connected / inactive / idle state (S100). Here, UE 1710 may acquire and configure parameters (e.g., CellReselection) including specific conditions (TAC list) for cell reselection within the RRC message and frequency information, SMTC, and other information. Then, UE 1710 may transition to an RRC idle state (S105). For example, if a certain amount of time has passed or an RRC release message is received, UE 1710 may transition to an RRC idle state. Here, UE 1710 in an RRC idle state resides on TN cell A 1720 (S110) and may perform frequency measurements based on the configured parameters. In detail, UE 1710 may perform intra-frequency / inter-frequency frequency measurements based on parameters (e.g., Cellreselection) including frequency information, SMTC, and other information. Then, UE 1710 may request cell reselection with a new cell based on UE mobility (S115). For example, UE 1710 may select TN cell B 1730 through a cell reselection process. UE 1710 may receive an RRC message (e.g., system information) of TN cell B 1730, and may receive a parameter having TAC#F associated with TN cell B 1730 (S120). Here, TAC#F may not be included in the TAC list. Therefore, UE 1710 camping on TN cell B 1730 may not perform NTN cell measurement and search (S125). UE 1710 may reselect a new cell based on UE mobility (S130). UE 1710 may select TN cell C 1740 through a cell reselection process. Then, UE 1710 may receive an RRC message (e.g., system information) of TN cell C 1740, and may receive a parameter having TAC#B associated with TN cell C. For example, TAC#B may be included in the TAC list. Therefore, the UE 1710 (S140) camping on the TN cell C 1740 may perform NTN cell measurement and search. That is, the UE 1710 may verify the signal strength and signal quality of the TN cell C 1740 as a serving cell, and if they are less than a specific value, may perform NTN cell measurement and search (S145).

[0288] As another example, the UE 1710 may perform NTN cell measurement and search based on the TAC list without a process of verifying the signal strength and signal quality of the TN cell C 1740 as a serving cell.

[0289] Here, at least one TAC represented as a 24-bit string may be configured in the TAC list. For example, although TAC#B and TAC#C each including a 24-bit string may be included Fig.17 in the TAC list, but this is merely an example and may not be limited to the above embodiment.

[0290] Moreover, the TAC may be configured differently depending on the PLMN (MCC+MNC). As another example, a UE in an RRC idle / inactive state may have multiple PLMNs in which the UE may reside. Here, the RA may be configured to have multiple TACs for each PLMN. Therefore, the network may configure a TAC list for each PLMN, or may configure a TAI in the UE. Here, since the TAI includes a PLMN and a TAC, multiple TAIs may be configured based on the TAC list. In addition, the TAC list is merely an example and may not be limited to the above names.

[0291] Fig.18 The method of the cell list-based measurement process applicable to the present disclosure is shown. Fig.18 , the coverage of NTN cell A can be determined based on satellite 1810. Here, a UE in an RRC idle state can perform initial access and then can be assigned a registration area (RA) as an area in which the UE can move without performing a registration update from the AMF. The RA may include multiple TACs. As a detailed example, if the UE is assigned an RA with TACs A, B, and C, the UE in an RRC idle state can move to a cell with TACs A, B, and C without performing a registration update procedure from the AMF. On the other hand, if UE 1620 moves to a cell with TAC D, UE 1820 can perform a registration update procedure to the AMF and then can be assigned a new RA.

[0292] Here, reference Fig.18 , NTN cells and TN cells may overlap. Here, TAC may refer to a geographically fixed location. Therefore, each cell of a base station may have a specific TAC identifier. A TAC identifier may be assigned from the AMF to the UE. Fig.18RA of all TACs (TAC 3 to TAC 18) shown, but this is only an example and is not limited to the above embodiment. That is, the UE can move within the RA without performing the registration update process, and can reside on a cell with a single TAC within the RA. For example, in a state where the UE exists in the TAC 18 area, the UE can reside on the TN cell 3 with TAC 18, and when the UE moves to TAC 7, the UE can perform camping on the NTN cell because there is no TN cell with a sufficiently strong signal strength. Here, since NTN cell A serves a wider area than the TN cell, NTN cell A can send multiple TACs to the UE through system information. The UE can derive the TAI by selecting a single TAC belonging to the RA from the multiple TACs obtained through the system information. Here, for example, a UE in an RRC idle state can receive the configuration of cell reselection parameters for camping through an RRC message (e.g., RRC release, SIB2,3,4). That is, when the UE that has been converted to the RRC idle state receives the configuration of the cell reselection parameters for the NTN cell from the TN cell 3 at the TAC 18 position, the UE can continuously search for the NTN cell within the RA. Here, since the NTN cell exists within the RA, the network can configure the cell reselection parameters of the NTN cell using the RRC message. However, since the UE cannot reside on the NTN cell in areas other than TAC 4, 5, 6, 7, 8, 10 and 11 served by the NTN cell A, performing a cell search may increase unnecessary power consumption. In addition, since the TN cell supports a higher QoS than the NTN cell, it may be unnecessary for the UE residing on the TN cell to reside on the NTN cell through cell reselection. However, based on Table 6 above, in an area where the signal strength of the serving cell is insufficient and the SSB of the NTN cell is verifiable, the UE residing in the TN cell may need an NTN cell search. As a specific example, when the signal strength at the cell edge is insufficient, the UE residing in the TAC 10 of the TN cell 5 may need to perform a cell search for the NTN cell A. Therefore, the power consumption of the RRC idle UE can be reduced through the process of the UE searching for the NTN cell in a specific cell.

[0293] In more detail, the network may include cell 5 1821 and cell 6 1822 in the cell list, which are capable of detecting the SSB of NTN cell A having a TAC served by NTN cell A for NTN cell search. The network may set NTN cell reselection parameters including a cell list, and may configure the parameters in the UE through an RRC message. For example, a UE present in TAC 18 may receive the configuration of NTN cell reselection parameters and a cell list (TN cells 5 and 6) through an RRC message (e.g., system information, RRC release) in TN cell 3. When the UE resides on a TN cell 3 that is not included in the cell list in TAC 18, the UE may perform only the configured TN cell search without performing an NTN cell search. On the other hand, if the UE moves to TAC 15 according to UE mobility, the UE may reside on TN cell 8 having TAC 15 because the UE performs only a search for TN cells. On the other hand, if the UE resides on a TN cell (e.g., TN cell 5 1821 and TN cell 6 1822) indicated by the cell list according to UE mobility, the UE may perform an NTN cell search based on the configured NTN cell reselection parameters. For example, although the UE is residing on a TN cell indicated by the cell list, the UE needs to prioritize the TN cell because the TN cell supports a higher QoS. Therefore, the UE residing on the TN cell needs to perform an NTN cell search considering the process of verifying the signal strength of the serving cell and the cell list.

[0294] Fig.19 FIG. 4 shows a NTN cell measurement signaling process based on a cell list applicable to the present disclosure. Fig.19, UE 1910 may receive an RRC message from TN cell A 1920 in an RRC connected / inactive / idle state (S200). Here, the UE may acquire and configure a parameter (e.g., Cellreselection) including a specific condition (cell list) for cell reselection within the RRC message and frequency information, SMTC, and other information. Then, UE 1910 may transition to an RRC idle state (S205). For example, if a certain amount of time has passed or an RRC release message is received, UE 1910 may transition to an RRC idle state. Here, UE 1910 in an RRC idle state resides in TN cell A 1920 (S210) and may perform frequency measurements based on the configured parameters. In detail, UE 1910 may perform intra-frequency / inter-frequency frequency measurements based on parameters (e.g., Cellreselection) including frequency information, SMTC, and other information. Then, UE 1910 may request cell reselection with a new cell based on UE mobility (S215). For example, UE 1910 may select TN cell B 1930 through a cell reselection process. UE 1910 may receive an RRC message (e.g., system information) of TN cell B 1930, and may receive a parameter having TAC#F and cell ID (cell B) associated with TN cell B 1930 (S220). Here, cell B may not be included in the cell list. Therefore, UE 1910 camping on TN cell B 1930 may not perform NTN cell measurement and search (S225). Then, UE 1910 may reselect a new cell based on UE mobility (S230). UE 1910 may select TN cell C 1940 through a cell reselection process. Then, UE 1910 may receive an RRC message (e.g., system information) of TN cell C 1940, and may receive a parameter having TAC#B and cell ID (cell C) associated with TN cell C (235). For example, cell C may be included in the cell list. Therefore, the UE 1910 (S240) camping on the TN cell C 1940 may perform NTN cell measurement and search. That is, the UE 1910 may verify the signal strength and signal quality of the TN cell C 1940 as a serving cell, and if they are less than a specific value, the NTN cell measurement and search may be performed (S245). As another example, the UE 1910 may perform NTN cell measurement and search without the process of verifying the signal strength and signal quality of the TN cell C 1940 as a serving cell.

[0295] Here, the cell ID may refer to a cell identifier. Here, the cell ID may include a 36-bit string and may include a gNB ID and a cell identifier. The gNB ID may include 22 bits or 32 bits. Therefore, the cell identifier may be represented as 14 bits or 4 bits. For example, when 22 bits are used to divide the gNB ID, an operator may assign 4194305 IDs to a macro cell or a small cell. Here, a 14-bit cell identifier may be assigned considering 250 DUs in a CU-DU structure and 12 cells per DU. Therefore, in Fig.19 In the present invention, the cell list may include a 16-bit string including the gNB ID and the cell identity of the cell C. In addition, the cell ID may be configured differently based on the PLMN (MCC+MNC). For example, a UE in an RRC idle / inactive state may have multiple PLMNs on which the UE may reside. Here, the RA may be configured to have multiple TACs for each PLMN. The network may configure a cell list for each PLMN, or may configure the NR cell global identifier (NCGI) in the UE. Here, since the NCGI includes the PLMN and the cell ID, multiple NCGIs may be configured based on the cell list. In addition, for example, the cell list is only an example and may not be limited to the above names.

[0296] Fig. 20 and 21 A method of performing measurements based on a RAN Area Code (RAC) applicable to the present disclosure is shown.

[0297] refer to Fig. 20, a cell ID (or cell identity) refers to a parameter used to identify a cell, and a single independent value can be assigned to each cell within a PLMN. The UE can verify the PLMN information and the tracking area code (TAC), RAN area code (RAC), and cell ID associated with the information from the PLMN identity information list (PLMN-IdentityInfoList) within the system information (e.g., SIB1). Here, the TAC and cell ID are the same as above. In addition, the RAC may refer to a parameter that divides a specific RAN area into up to 255 areas in a single TAC. That is, the TN cell may send the TAC in which the TN cell exists and the RAC information associated with the TAC to the UE. The UE may determine whether to perform a mobility update to the network based on the received information. For example, the mobility update may be the aforementioned registration update. As another example, the mobility update may be a RAN-based Notification Area Update (RNAU) procedure performed by a UE in an RRC inactive state. For example, when a UE in an RRC inactive state leaves a RAN Notification Area (RNA) cell list, the UE in an RRC inactive state needs to receive configuration of a new RNA cell list, and for this purpose, an RNAU procedure may be performed. That is, the UE in an RRC inactive state may perform an RNAU procedure based on UE mobility.

[0298] For example, refer to Fig. 20 , RAC can be configured in TAC. That is, multiple RACs can be configured in each TAC. The TN cell may also have at least one TAC and RAC of its own. As a detailed example, TN cell 1 2010 may have TAC#A and RAC 1, 2, 3, and 4. TN cell 2 2020 may have TAC#A and RAC 7, 8, 9, and 10, and TN cell 4 2040 may have TAC#C and RAC 1, i.e., each cell may have a TAC and a RAC according to the location of the service coverage. Here, each cell may notify the UE of its TAC and RAC through system information. The UE may verify the TAC and RAC of the cell through the system information.

[0299] In addition, reference Fig.21, the coverage of NTN cell A can be determined based on satellite 2110. A UE in RRC idle state can perform initial access and then be assigned a registration area (RA) as an area where the UE can move without performing a registration update from the AMF. Here, the RA includes multiple TACs. As a detailed example, if the UE is assigned an RA with TACs A, B, and C, the UE in RRC idle state can move to a cell with TACs A, B, and C without performing a registration update procedure from the AMF. On the other hand, if the UE moves to a cell with TAC D, the UE can perform a registration update procedure to the AMF and then be assigned a new RA.

[0300] For example, the AMF may assign to the UE a Fig.21 The RA of all TACs (TAC A, B, C, D, E, F and G) shown, but this is just an example and is not limited to the above embodiment. That is, the UE can move within the RA without the registration update process to the AMF and can reside on a cell with a single TAC within the RA.

[0301] For example, in a state where the UE exists in the TAC#B area, the UE can camp on the TN cell 6 with TAC#B around the UE. Then, when the UE moves to TAC#D based on UE mobility, the UE can perform camping on the NTN cell because there is no TN cell with a sufficiently strong signal strength. Here, since the NTN cell A serves a wider area than the TN cell, multiple TACs can be sent to the UE through system information. The UE can derive the TAI by selecting a single TAC belonging to the RA from the multiple TACs included in the system information.

[0302] In addition, a UE in an RRC idle state can receive configuration of cell reselection parameters for camping through an RRC message (e.g., RRC release, SIB2, 3, 4). That is, when a UE that has transitioned to an RRC idle state at a TAC#B position receives configuration of cell reselection parameters for an NTN cell from a TN cell 6, the UE needs to continuously search for NTN cells within the RA. Here, since the NTN cell exists within the RA, the network can configure the cell reselection parameters of the NTN cell using an RRC message. However, since the UE cannot camp on NTN cells in areas other than TAC#A, D, E, F, and G served by NTN cell A, performing a cell search may increase unnecessary power consumption. In addition, since TN cells support higher QoS than NTN cells, UEs camping on TN cells may not need to camp on NTN cells through cell reselection.

[0303] Therefore, based on the above Table 6, in an area where the signal strength of the serving cell is insufficient and the SSB of the NTN cell can be received, the UE camping on the TN cell may need an NTN cell search. As a detailed example, if the signal strength on the cell edge is insufficient, the UE camping on the TN cell 3 with TAC#A, RAC 3, 4, 5, and 6 or the TN cell 4 with TAC#C, RAC 1 may perform a cell search for the NTN cell A. Therefore, by the process of searching the NTN cell in a specific cell by the UE, the power consumption of the UE in the RRC idle state can be reduced.

[0304] In more detail, the network may include a combined list of TAC#A, RAC 3, 4, 5, and 6 and TAC#C, RAC 1 in the RAC list, which is capable of detecting the SSB of NTN cell A served by NTN cell A for NTN cell search. The network may then set the NTN cell reselection parameter and may configure the parameter in the UE through an RRC message. For example, a UE present in TAC#B may receive the configuration of the NTN cell reselection parameter and the RAC list (TAC#A, RAC 3, 4, 5, and 6 and / or TAC#C, RAC 1) through an RRC message (e.g., system information, RRC release) in TN cell 6. Since the UE is residing on TN cell 6 in TAC#B with a TAC and RAC that are not configured in the RAC list, the UE may perform only a TN cell search without performing an NTN cell search. In addition, if the UE moves to TAC#C based on UE mobility, the UE may be residing on TN cell 5 with TAC#C because the UE performs only a search for TN cells. Here, the TAC and RAC combination of TN cell 5 may not be configured in the RAC list. Therefore, the UE may not perform an NTN cell search. On the other hand, in the case of residing on a TN cell (e.g., TN cells 1, 3, 4) having a TAC and RAC combination indicated in the RAC list according to UE mobility, the UE may perform an NTN cell search based on the configured NTN cell reselection parameters. In addition, although the UE is residing on a TN cell having a TAC and RAC combination indicated in the RAC list, the UE may prioritize the TN cell because the TN cell supports a higher QoS. Therefore, the UE residing in the TN cell needs to perform an NTN cell search by verifying the signal strength of the serving cell and the process of the RAC list.

[0305] Fig. 22 FIG. 4 shows an NTN cell measurement signaling process based on a RAC list applicable to the present disclosure. Fig. 22, UE2210 can receive an RRC message from TN cell A2220 in an RRC connected / inactive / idle state (S300). Here, the UE can obtain and configure parameters (e.g., Cellreselection), which include specific conditions (RAC list) for cell reselection and frequency information, SMTC and other information within the RRC message. Then, UE 2210 can transition to an RRC idle state (S305). For example, if a certain amount of time has passed or an RRC release message is received, UE 2210 can transition to an RRC idle state. Here, UE 2210 in an RRC idle state resides on TN cell A 2220 (S310) and can perform frequency measurements based on the configured parameters. In detail, UE 2210 can perform intra-frequency / inter-frequency frequency measurements based on parameters (e.g., Cellreselection) including frequency information, SMTC and other information. Then, UE 2210 can request cell reselection with a new cell based on UE mobility (S315). For example, the UE 2210 may select the TN cell B 2230 through the cell reselection process. The UE 2210 may receive an RRC message (e.g., system information) of the TN cell B 2230, and may receive a parameter having TAC#B and RAC#10 associated with the TN cell B 2230 (S320). Here, TAC#B and RAC#10 may not be included in the RAC list. Therefore, the UE 2210 camping on the TN cell B 2230 may not perform NTN cell measurement and search (S325). Then, the UE 2210 may reselect a new cell based on UE mobility (S330). The UE 2210 may select the TN cell C 2240 through the cell reselection process. Then, the UE 2210 may receive an RRC message (e.g., system information) of the TN cell C 2240, and may receive a parameter having TAC#B and RAC#1 associated with the TN cell C 2240 (S335). For example, cells TAC#B and RAC#1 may be included in the RAC list. Therefore, the UE 2210 (S340) camping on the TN cell C 2240 may perform NTN cell measurement and search. That is, the UE 2210 may verify the signal strength and signal quality of the TN cell C 2240, and if they are less than a specific value, the NTN cell measurement and search may be performed (S345). As another example, the UE 2210 may perform NTN cell measurement and search without the process of verifying the signal strength and signal quality of the TN cell C 2240 as a serving cell.

[0306] Here, at least one TAC represented as a 24-bit string can be configured in the RAC list. In addition, each TAC can include at least one RAC integer. Here, the TAC and RAC can be configured differently according to the PLMN (MCC+MNC). In addition, for example, a UE in an RRC idle / inactive state can have multiple PLMNs, and the UE can reside on these PLMNs. The RA can be configured to have multiple TACs for each PLMN. The network can configure the RAC list for each PLMN, or the RAC can be configured according to the TAI in the UE. Here, since the TAI includes the PLMN and the TAC, multiple TAI and RAC combinations can be configured in the RAC list. In addition, the RAC list is only an example and is not limited to the name.

[0307] Fig.23 A method for performing measurements based on at least one of a TAC, a cell, and a RAC list applicable to the present disclosure is shown. For example, when multiple cells exist within a single TAC, the network may provide the UE with at least one of a TAC, a cell, and a RAC list for NTN cell measurement, which may result in reduced power consumption.

[0308] For example, receiving Fig.16 A UE with a configuration of a TAC list (e.g., TAC 10 and 11) can measure NTN cells based on the signal strength of the serving cell while camping on TN cells 5, 6, 9, and 10 with TAC 10 or 11. Here, if the UE camps on TN cells 9 and 10, the UE may not need to perform NTN cell measurement due to the presence of neighboring TN cells 5 or 6. Therefore, the network may configure at least one of one or more combinations of TAC, cell, and RAC lists in the UE for NTN cell measurement. As a specific example, the above combination may be a TAC and a cell list, or an RAC and a cell list, but this is merely an example and is not limited to the above embodiments.

[0309] Fig.24 FIG. 1 shows an NTN cell measurement signaling process based on at least one of a TAC, a cell, and a RAC list applicable to the present disclosure. Fig.24, UE 2410 may receive an RRC message from TN cell A 2420 in an RRC connected / inactive / idle state (S400). Here, the RRC message may include a parameter (e.g., CellReselection) including a specific condition (RAC list) for cell reselection and frequency information, SMTC, and other information. Then, UE 2410 may transition to an RRC idle state (S405). For example, if a certain amount of time has passed or an RRC release message is received, UE 2410 may transition to an RRC idle state. Here, UE 2410 in an RRC idle state is camping on TN cell A 2420 (S410), and frequency measurements may be performed based on configured parameters. In detail, UE 2410 may perform intra-frequency / inter-frequency frequency measurements based on parameters (e.g., Cellreselection) including frequency information, SMTC, and other information. Then, UE 2410 may request cell reselection with a new cell based on UE mobility (S415). For example, UE 2410 may select TN cell B 2430 through a cell reselection sorting process. UE 2410 may receive an RRC message (e.g., system information) of TN cell B 2430, and may receive a parameter having TAC#B and cell ID (cell B) associated with TN cell B 2430 (S420). Here, TAC#B may be included in the TAC list, but cell ID (cell B) may not be included in the cell list. Therefore, UE 2410 camping on TN cell B 2430 may not perform NTN cell measurement and search (S425). Then, UE 2410 may reselect a new cell based on UE mobility (S430). UE 2410 may select TN cell C 2440 through a cell reselection sorting process. Then, UE 2410 may receive an RRC message (e.g., system information) of TN cell C 2440, and may receive a parameter having TAC#B and cell ID (cell C) associated with TN cell C (S435). For example, cell TAC#B and cell ID (cell C) may be included in a TAC list and a cell list. Therefore, UE 2410 (S440) residing on TN cell C 2440 may perform NTN cell measurement and search. That is, UE 2410 may verify the signal strength and signal quality of TN cell C 2440 as a serving cell, and if they are less than a specific value, may perform NTN cell measurement and search (S445). As another example, UE 2410 may perform NTN cell measurement and search without the process of verifying the signal strength and signal quality of TN cell C 2440 as a serving cell. Although Fig.24An embodiment based on a combination of a TAC list and a cell list is shown, but a combination of a RAC and a cell list is also possible, which is not limited to a specific embodiment.

[0310] Here, for example, TAC and RAC and cell ID can be configured differently based on PLMN (MCC+MNC). In addition, a UE in RRC idle / inactive state can have multiple PLMNs, and the UE can reside on these PLMNs. Therefore, RA can be configured to have multiple TACs for each PLMN. The network can configure at least one of the TAC, cell and RAC lists for each PLMN. As another example, the network can configure at least one combination of TAI, NCGI and RAC in the UE for each PLMN. Here, TAI is configured using PLMN and TAC, and NCGI is configured using PLMN and cell ID. Therefore, multiple TAI, NCGI and RAC combinations can be configured in the TAC and cell list or the RAC and cell list. In addition, for example, the TAC and cell list and the RAC and cell list are merely examples and may not be limited to these names.

[0312] Fig.25 FIG. 2 shows a synchronization signal block (SSB) configuration applicable to the present disclosure. Fig.25 , the cell can provide SSB configuration information to the UE through system information (e.g., SIB1). Fig.25 It can be shown that the subcarrier spacing (SCS) is 15kHz, the frequency band is 3 to 6GHz, and the maximum number of SSBs available at 6GHz in SIB1 is 8. Fig.25 In , the inOnGroup indicating the SSB used for actual transmission among the eight SSBs may be (1 1 1 1 1 1 0 1), but this is merely an example and is not limited to the above embodiment. Here, the symbol position of the SSB may be predefined for each specific subcarrier spacing and frequency band. For example, in Fig.25 , the SSB start symbol of the candidate SSB can be determined by the following Equation 3, and the SSB can be transmitted at symbol indexes 2, 8, 16, 22, 30, 36, 44 and 50 based on Equation 3.

[0313] [Equation 3]

[0314] {2,8}+14n(n:0,1,2,3)

[0316] For example, the SSB actually transmitted in the network may be different depending on the environment. Therefore, the network can use a bitmap format (e.g., inOnGroup) to notify the UE of the actual SSB transmission through SIB1. Fig.25 , since InOnGroup is configured as (1 1 1 1 1 1 0 1), SSBs 2510, 2520, 2530, 2540, 2550, 2560, and 2570 of eight SSBs except SSB#6 may be transmitted. For example, if the frequency band is 3 GHz or less, the maximum number of SSBs may be 4, and the SSB start symbol of the candidate SSB may be as shown in Equation 4 below, and the SSB may be transmitted from symbols 2, 8, 16, and 22.

[0317] [Equation 4]

[0318] {2,8}+14n(n:0,1)

[0320] As another example, in FR2, the maximum number of SSBs may be 64. Here, SIB1 may divide 64 SSBs into 8 groups in sequence, and may include group presence (groupPresence) indicating from which group the SSB is transmitted. As a detailed example, when groupPresence is (1 0 0 0 0 0 0 1) and inOneGroup is configured as (1 1 0 0 0 0 0 0), the index of the SSB actually transmitted may be 0, 1, 56, and 57. Here, the SSB burst set may be configured within 5 ms and may be repeatedly transmitted at a specific interval.

[0321] Fig.26 FIG. 4 shows an SMTC window configuration configured in a network for measuring a specific frequency applicable to the present disclosure. Fig.26 , the network may configure the SMTC window for neighboring cell 1 2610 and neighboring cell 2 2620 in the UE. That is, the network may instruct the UE to perform measurements during a specific time period per specific period in the time domain, so that the UE may measure the SSB of neighboring cell 1 2610 and neighboring cell 2 2610, and may provide the configuration information. Here, in consideration of power consumption, the UE may configure the SMTC window period to be greater than the SSB period. For example, the network may set the SMTC window configuration for each SSB period of neighboring cell 2 2620 so that the UE may measure the SSB of neighboring cell 2 2620. In addition, the network may set the SMTC window configuration to be longer than the SSB period of neighboring cell 1 2610 so that the UE may measure the SSB of neighboring cell 1 2610.

[0322] Here, the UE may perform an operation for SSB search in the SMTC window duration based on the step size of the GSCN in the NR-ARFCN indicating the specific frequency band used for the above-mentioned intra-frequency / inter-frequency measurement.

[0323] For example, when TN frequency information for cell reselection in an NTN cell is configured in the UE, the UE can perform SSB measurement for each set SMTC window configuration, and power consumption can continue accordingly. Taking the above into account, it may be necessary to not perform the measurement process according to specific conditions (TAC list and / or cell list and / or RAC list).

[0324] For example, since the TN cell can satisfy a higher QoS than the NTN cell, the UE can always prioritize the TN cell. That is, when the NTN cell is configured for measurement of the TN cell in the UE, the NTN cell can always set the TN priority to high. Therefore, it is necessary to increase the conditional TN cell measurement and search process. On the contrary, when the UE resides in the TN cell, if the signal strength of the serving cell decreases, the UE can perform measurements on the low-priority NTN cell. Here, sometimes the UE residing in the TN cell does not need measurement of the NTN cell. Therefore, it is necessary to increase the conditional NTN cell measurement and search process to reduce the power consumption of the UE. For example, the UE can measure the NTN frequency according to the above-mentioned specific conditions (at least one combination of the TAC list, the cell list and the RAC list), and the process for the measurement is described below. When the inter-frequency information is configured in the UE based on the RRC message (e.g., system information, RRC release), the UE can perform measurements according to specific conditions (at least one combination of the TAC list, the cell list and the RAC list).

[0325] For example, Table 7 may represent a method for performing measurement by the UE. In detail, as a case where the priority of the inter-frequency or inter-RAT frequency is equal to or lower than the current frequency, when the signal strength and signal quality of the serving cell are less than a specific value, the UE may perform measurement considering the aforementioned specific conditions (at least one combination of the TAC list, the cell list, and the RAC list), which may be as shown in Table 7 below.

[0326] As another example, if the priority of the inter-frequency or inter-RAT frequency is equal to or lower than the current frequency, the UE may perform measurement considering the above-mentioned specific conditions (at least one combination of the TAC list, the cell list, and the RAC list).

[0327] [Table 7]

[0328]

[0330] Here, a specific condition (at least one combination of a TAC list, a cell list, and a RAC list) may be configured for all NTN bands in the RRC message. As another example, the specific condition (at least one combination of a TAC list, a cell list, and a RAC list) may be configured only for a specific NTN band and is not limited to a specific embodiment.

[0331] As a detailed example, if the above-mentioned specific conditions (at least one combination of TAC list, cell list and RAC list) are configured as a single common parameter within the RRC message for all NTN frequencies, the common parameter may be configured in at least one of SIB2, SIB3 and SIB4. If the above-mentioned specific conditions (at least one combination of TAC list, cell list and RAC list) are met, the UE may perform measurements for all NTN frequencies, which may be shown in Table 7 above. As another example, if the above-mentioned specific conditions (at least one combination of TAC list, cell list and RAC list) are configured only for a specific NTN band, the network may configure the above-mentioned specific conditions (at least one combination of TAC list, cell list and RAC list) for each NTN band. The UE may only measure NTN frequencies that meet the above-mentioned specific conditions (at least one combination of TAC list, cell list and RAC list). Here, the NTN frequency may refer to a specific frequency band and is not limited to a specific embodiment.

[0332] As another example, the condition for the UE to perform measurement for the intra-frequency cell reselection indicated by the system information may be as shown in the following Table 8. That is, the UE may compare the signal strength and signal quality of the serving cell with a specific value.

[0333] [Table 8]

[0334]

[0336] Here, the UE may perform NTN frequency measurement according to the above-mentioned specific conditions (at least one combination of the TAC list, the cell list, and the RAC list). For example, when the UE receives and configures intra-frequency information (e.g., system information, RRC release) through an RRC message, the UE may verify the above-mentioned specific conditions (at least one combination of the TAC list, the cell list, and the RAC list), and then perform the measurement, which may be as shown in Table 9 below.

[0337] [Table 9]

[0338]

[0340] In addition, for example, if the t-service of the serving cell exists in the system information (e.g., SIB19), the UE may perform intra-frequency measurements before the T-service, regardless of the conditions shown in Table 9 below. Here, T-service may refer to the epoch time when the fixed cell serves the coverage area. As another example, the UE may always perform intra-frequency measurements for high priority, regardless of the conditions shown in Table 9.

[0341] As described above, for a UE that conditionally performs measurement of an NTN cell, the above-mentioned specific conditions (at least one combination of a TAC list, a cell list, and a RAC list) for indicating or measuring TN / NTN may be added to parameters within the existing system information. That is, as the existing system information, in addition to the inter-frequency / intra-frequency information priority, SMTC, NR-Absolute Radio Frequency Channel Number (ARFCN), band list, and other information for cell reselection, the above-mentioned specific conditions (at least one combination of a TAC list, a cell list, and a RAC list) for indicating or measuring TN / NTN may be added. That is, the above-mentioned specific conditions (at least one combination of a TAC list, a cell list, and a RAC list) may be included in the parameter configuration for cell reselection. Here, as described above, for NTN frequency measurement, the above-mentioned specific conditions (at least one combination of a TAC list, a cell list, and a RAC list) may be configured with a single common parameter for all frequency bands, or may be configured with specific parameters for a specific NTN frequency band.

[0343] 2. Conditional TN cell search (frequency measurement)

[0344] For example, with respect to conditional TN cell search, a method for performing a cell search based on a reference position of an adjacent TN cell (hereinafter, method 2-1) and a method for performing a cell search based on a reference position of an adjacent NTN cell (hereinafter, method 2-2) may be considered. Here, in the NTN system, each of method 2-1 and method 2-2 may be applied independently. As another example, method 2-1 may be applied preferentially, and method 2-2 may be applied in some cases where method 2-1 is difficult to apply. However, it is not applied to a specific implementation scheme. Below, for clarity of description, description is made based on each of method 2-1 and method 2-2, but each method may be applied by being associated with or complemented with each other, and is not limited to a specific embodiment.

[0346] Method 2-1 (Cell search based on neighboring TN cell reference positions)

[0347] Fig. 27 A method for performing a cell search based on a neighboring TN cell reference position applicable to the present disclosure is shown. Fig. 27, the UE may perform measurements of the TN frequency based on the reference point (or reference position). Here, the UE in the RRC idle / inactive state may reduce power consumption by performing measurements on the TN frequency based on predetermined conditions. For example, the network may configure a specific point where a TN cell exists in the UE as a reference location through at least one RRC message (e.g., system information, RRC release, RRC reconfiguration). For example, the reference location may be a specific point where a TN cell exists. As another example, the reference location may be set to a preset specific location based on the TN cell, and may not be limited to a specific embodiment.

[0348] Here, the UE may verify whether the UE's location information is valid. When the UE's location information is valid, the UE may compare the difference between the reference point configured by the network and the UE with a threshold. Here, if the distance between the reference point configured by the network and the UE is less than the threshold, the UE may perform TN frequency measurement.

[0349] As a detailed example, Fig. 27 UE 2720 within satellite 1 2710 of may verify the distance from reference point 1 (reference position 1) 2730. Here, if the distance from reference point 1 2730 is greater than or equal to a threshold, UE 2720 may not perform TN frequency measurement. On the other hand, UE 2750 in satellite 2 2740 may receive the configuration of two reference points (reference position 1 2761 and reference position 2 2762) from the network. However, this is merely to describe a clear example and is not limited to the above embodiments. Here, when the position of UE 2750 is valid, UE 2750 may verify the distance from the reference position. Then, UE 2750 may determine whether to perform measurements for TN frequencies based on a threshold. In view of the above, the NTN cell may provide the UE with information (e.g., reference position, distance threshold, associated frequency index) to assist TN cell measurements.

[0350] As a detailed example, NTN specific system information (e.g., SIB19) may include information that assists the above-mentioned TN cell measurement. As another example, the information that assists the above-mentioned TN cell measurement may also be included in the existing system information and is not limited to a specific embodiment. The UE may verify the information about the TN neighboring cell through the system information received from the serving cell, and thereby determine whether to perform the TN frequency measurement.

[0351] Here, the information about the TN neighboring cells and the information for cell reselection may be associated. For example, when the reference point of the neighboring cell is provided to the UE as system information, the UE may determine the frequency band in which the UE performs measurement and the SMTC window associated therewith based on the effective location information of the UE and the distance between the reference points and the threshold. Taking the above into account, the information about the neighboring cells and the measurement frequency band information may be associated so that the UE may determine the TN frequency measurement.

[0352] Fig.28 A TN cell configuration applicable to the present disclosure is shown. As described above, information about TN neighboring cells and information for cell reselection may be related. For example, the NTN cell may be configured based on satellite 1 2810. Here, the UE 2820 may perform measurements of TN neighboring cells in consideration of a reference point (or reference position) of the TN cell. Neighboring cell information (neighboring cell information) of TN cell 1 refers to information used to determine measurements, and may include reference position 1 2831 of TN cell 1 and a distance threshold. In addition, the neighboring cell information of TN cell 1 may include at least one of a TN index and a frequency band position (NR-ARFCN) of TN cell 1 as information for cell reselection. Here, the information for cell reselection may be associated with frequency information (e.g., system information, RRC release) within an RRC message. As a detailed example, when NR-ARFCN is designated as "A" in TN cell 1, information for cell reselection may be associated with frequency information (InterFreqCarrierFreqInfo or MeasIdleCarrierNR 1, 2) in which NR-ARFCN is set to "A". As another example, when the TN index is indicated as '1' in TN cell 1, information for cell reselection may be associated with frequency information (InterFreqCarrierFreqInfo or MeasIdleCarrierNR 1).

[0353] In addition, when NR-ARFCN is designated as 'B' in TN cell 2 2832, information for cell reselection may be associated with frequency information (InterFreqCarrier FreqInfo or MeasIdleCarrierNR 3) in which NR-ARFCN is set to 'B'. As another example, when the TN index is indicated as '2' in TN cell 2 2832, information for cell reselection may be associated with frequency information (InterFreqCarrier FreqInfo or MeasIdleCarrier NR 2,3).

[0354] In more detail, if the distance between UE 2820 and TN cell 1 is less than a distance threshold, UE 2820 may verify the frequency information associated with at least one of the NR-ARFCN and the TN index. Then, UE 2820 may verify the SSB in the time / frequency corresponding to the SMTC and NR-ARFCN associated with the verified frequency information. In addition, if the distance between UE 2820 and TN cell 22832 is greater than the distance threshold, UE 2820 may verify the frequency information associated with the NR-ARFCN and the TN index, and may not perform the process of verifying the SSB in the time / frequency corresponding to the SMTC and NR-ARFCN associated with the frequency information. That is, UE 2820 may perform the process of verifying the SSB in the time / frequency corresponding to the SMTC and NR-ARFCN associated with the corresponding frequency information only within the distance threshold based on the effective current position of UE 2820 and the reference position information configured for each TN cell.

[0355] Here, the reference location information and distance threshold configured for each TN cell may be included and thus configured in the frequency information (InterFreqCarrier FreqInfo or MeasIdleCarrierNR). For example, frequency information 1 (InterFreqCarrier FreqInfo or MeasIdleCarrier NR 1) may include NR-ARFCN and SMTC information. In addition, frequency information 1 may further include reference location information and distance threshold information. UE 2820 may determine whether to perform the process of verifying SSB from time / frequency configuration (SMTC, NR-ARFCN) through the information used to determine the measurement (reference location information, distance threshold), which is the same as described above. Here, the reference location information about the location of the TN cell may be as shown in Table 10 below. Here, Table 10 may refer to information expressed in latitude and longitude.

[0356] [Table 10]

[0357]

[0359] For example, as described above, since the TN cell can satisfy a higher QoS than the NTN cell, the UE can always give priority to the TN cell. That is, in the case where the NTN cell configures the TN cell measurement in the UE, the priority of the TN cell can always be set to high. The UE can always measure the TN cell based on the aforementioned configuration. However, since the UE needs to measure the configured TN cell all the time, power may be consumed continuously. Therefore, the UE can measure the TN frequency according to the above-mentioned specific condition (distance threshold) to reduce power consumption. In detail, during the process of the UE measuring the TN frequency, the UE can receive an RRC message (e.g., system information, RRC release). Here, the RRC message may include inter-frequency information. The UE can configure the measurement operation based on the inter-frequency information. Here, it may be necessary to verify the aforementioned operation of the specific condition (distance threshold), which can be shown in Table 11 below. That is, the UE can perform measurement based on whether the priority of the inter-frequency or inter-RAT frequency is higher than the priority of the current frequency, whether the signal strength and signal quality of the serving cell are greater than a specific value, and whether the distance between the reference position of the target cell and the UE is greater than the distance threshold, which can be shown in Table 11 below.

[0360] [Table 11]

[0361]

[0363] In addition, for example, the UE can measure the TN frequency according to the above-mentioned specific conditions (distance threshold), thereby reducing power consumption. In detail, during the process of the UE measuring the TN frequency, the UE can receive an RRC message (e.g., system information, RRC release). Here, the RRC message may include intra-frequency information. The UE can configure the measurement operation based on the intra-frequency information. Here, it may be necessary to verify the operation of the above-mentioned specific conditions (distance threshold), and this can be shown in Table 12.

[0364] That is, the UE can perform measurements based on whether the frequency is associated with an NTN cell or a TN cell, whether the signal strength and signal quality of the serving cell are greater than a specific value, and whether the distance between the reference position of the target cell and the UE is greater than a distance threshold, as shown in Table 11 below.

[0365] [Table 12]

[0366]

[0368] Method 2-2 (Cell search based on neighboring NTN cell reference positions)

[0369] Fig.29 1 shows the NTN cell reference location applicable to the present disclosure. For example, for the sake of clarity, Fig.29 In the example of configuring the reference location information in the area where the TN cell exists, the description is given, but it is not limited thereto. For example, the reference location may be configured as the edge of the TN cell. As another example, the reference location may be the reference location of the adjacent NTN cell.

[0370] refer to Fig.29 , multiple NTN cells may be configured based on satellite 1 2910. Here, the reference position of the neighboring cell may not be derived based on the TN cell, and may be derived based on the NTN neighboring cell. As a detailed example, there may be a case where the reference position of the TN cell may not be set due to security issues. In the above case, a cell search may be performed based on the reference position of the NTN cell. For example, in Fig.29 , cells A, B, C, D, E, F, and G may be NTN cells based on earth-fixed beams according to satellite 1 2910. Here, each NTN cell may provide reference location information to UE 2920. UE 2920 may control measurement based on the reference location information received from each NTN cell.

[0371] For example, if UE 2920 is camping in cell B, UE 2920 can obtain the reference position 2931 of cell B through system information. As another example, if UE 2920 is camping in cell G, UE 2920 can obtain the reference position 2931 of cell G through system information. Here, consider the case where a TN cell exists in a position overlapping with cells B, C, and D. Here, the network can control the measurement of the TN cell by providing the UE 2920 with the reference position of the neighboring cell.

[0372] As a detailed example, if UE 2920 is camping on cell B, cell B may provide the UE with a reference position 2931 of cell B (reference position of NTN cell B) and reference positions 2932, 2933 of neighboring cells (reference position of NTN cell C and / or reference position of NTN cell D) through an RRC message. UE 2920 may determine the measurement of the TN cell by the distance from at least one of the reference position 2931 of cell B as a serving cell and the reference positions 2932 and 2933 of the neighboring cells. In more detail, UE 2920 may determine whether the reference position 2931 of cell B as a serving cell is greater than a specific threshold. In addition, UE 2920 may verify whether the distance to the reference position of the neighboring cell is greater than a threshold. That is, UE 2920 may determine whether to perform TN cell measurement based on information comparing the reference position of the serving cell and the threshold and information comparing the reference position of the neighboring cell and the threshold.

[0373] For example, as described above, since the TN cell can meet a higher QoS than the NTN cell, the UE can always give priority to the TN cell. That is, when the NTN cell configuration is used for the measurement of the TN cell in the UE, the priority of the TN cell can always be set to high. The UE can always measure the TN cell based on the aforementioned configuration. However, since the UE needs to always measure the configured TN cell, power may be consumed continuously. Therefore, the UE can reduce power consumption by measuring the TN frequency according to the above-mentioned specific conditions (distance threshold). In detail, during the process of the UE measuring the TN frequency, the UE can receive an RRC message (e.g., system information, RRC release). Here, the RRC message may include inter-frequency information. The UE can configure the measurement operation based on the inter-frequency information. Here, it may be necessary to verify the operation of the above-mentioned specific conditions (distance threshold), and this can be shown in Table 13 below.

[0374] [Table 13]

[0375]

[0377] In addition, for example, the UE can reduce power consumption by measuring the TN frequency according to the above-mentioned specific condition (distance threshold). In detail, during the process of the UE measuring the TN frequency, the UE can receive an RRC message (e.g., system information, RRC release). Here, the RRC message may include intra-frequency information. The UE can configure the measurement operation based on the intra-frequency information. Here, it may be necessary to verify the operation of the above-mentioned specific condition (distance threshold), which can be shown in Table 14 below.

[0378] [Table 14]

[0379]

[0381] Fig.30 is a flow chart illustrating a method of performing a conditional NTN cell search applicable to the present disclosure.

[0382] Reference Fig.30, the UE may obtain condition information about cell reselection through an RRC message (S3010). Here, the condition information about cell reselection may be configured based on at least one of a TAC list, a RAC list, and a cell list. Here, for example, the UE may receive an RRC message and may transition to an idle state. Then, the UE may move from the first cell where it resides to the second cell based on the mobility of the UE (S3020). Here, the UE may receive an RRC message including measurement-related information for cell reselection from the second cell (S3030). For example, the measurement-related information for cell reselection may include at least one of a TAC list, a RAC list, and a cell ID. Then, the UE may verify whether a specific condition is met based on the measurement-related information for cell reselection received from the second cell (S3040). Here, as described above, the specific condition may be a condition for determining whether NTN cell measurement and search are required based on at least one of the above-mentioned TAC list, RAC list, and cell ID list. For example, as described above, when a specific condition is met based on the information obtained from the second cell, an NTN cell search may be performed (S3050).

[0383] Fig.31 is a flow chart showing a method for performing a conditional TN cell search to which the present disclosure may be applied. Fig.31 , the UE may obtain reference location information and distance threshold information about each cell in at least one cell through an RRC message (S3110). Here, the at least one cell may be a TN cell or an NTN cell. For example, in the case of a TN cell, the reference location information may be a specific point where the TN cell exists. As another example, the reference location information may be a location determined based on the TN cell, and is not limited to a specific embodiment. In the case of an NTN cell, the reference location information may be information derived based on the NTN cell. The UE may then derive distance condition information based on the distance threshold information and reference location information about each cell in at least one cell (S3120). Then, as described above, the UE may perform a TN cell search based on its current location and distance condition information (S3130).

[0384] Fig.32 is a diagram showing a first device and a second device that can be applied to the present disclosure.

[0385] Reference Fig.32, the first device (3200) and the second device (3250) communicate with each other. At this time, as an example, the first device (3200) can be a base station, and the second device (3250) can be a user equipment (UE) device. As another example, both the first device (3200) and the second device (3250) can be UE devices. That is, the first device (3200) and the second device (3250) can be devices that communicate with each other according to NR-based communication. As an example, the case where the first device (3200) is a base station and the second device (3250) is a UE device can be considered. At this time, the base station device 3200 may include a processor 3220, an antenna unit 3212, a transceiver 3214, and a memory 3216.

[0386] The processor 3220 performs baseband-related signal processing and may include a higher layer processor 3230 and a physical layer processor 3240. The higher layer processor 3230 may process the operation of a media access control (MAC) layer, a radio resource control (RRC) layer, or a higher layer thereof. The physical layer processor 3240 may process the operation of a physical (PHY) layer (e.g., uplink received signal processing, downlink transmission signal processing). In addition, in order to perform baseband-related signal processing, the processor 3220 may also control the operation of the base station device 3200 as a whole. The antenna unit 3212 may include one or more physical antennas, and may support multiple input multiple output (MIMO) transmission and reception in the case of including multiple antennas. In addition, beamforming may be supported. The memory 3216 may store information related to the operation of the base station device 3200, such as the processor 3220, software, operating system, application, etc., which has been calculated and processed, and may include components such as a buffer. The processor 3220 of the base station 3200 may be configured to implement the operation of the base station in the example described herein.

[0387] The UE device 3250 may include a processor 3270, an antenna unit 3262, a transceiver 3264, and a memory 3266. For example, in the present invention, the UE device 3250 may communicate with the base station device 3200. As another example, in the present invention, the UE device 3250 may perform SL communication with another UE device. That is, the UE device 3250 of the present invention refers to a device capable of communicating with at least one of the base station device 3200 and other UE devices, and is not limited to communicating with a specific device. The processor 3270 performs baseband-related signal processing and may include a higher layer processor 3280 and a physical layer processor 3290. The higher layer processor 3280 may process the operation of the MAC layer, the RRC layer, or a higher layer. The physical layer processor 3290 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 3270 may also control the operation of the UE device 3250 as a whole. The antenna unit 3262 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 3266 may store information related to the operation of the UE device 3250 of the processor 3270, software, operating system, application, etc., and may include components such as a buffer. The UE device 3250 according to the example of the present invention may be associated with a vehicle. For example, the UE device 3250 may be integrated into a vehicle, may be located in a vehicle, or may be located on a vehicle. In addition, the UE device 3250 according to the present invention may be the vehicle itself. In addition, the UE device 3250 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 3250 to which the present invention may be applied may include any communication device of various types that supports interactive services using side links, 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 side link operations or any type of communication device capable of performing relay operations as a sensor may be included.

[0388] 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 3250 according to the example of the present invention is described as being associated with a vehicle, at least one of the UEs may not be associated with a vehicle. This is merely an example and should not be construed as limiting the application of the present invention to the described example. In addition, the UE device 3250 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 3250 directly supports interactive services using a side link, it can also be used as a collaborative device supporting interactive services using a side link.

[0389] For example, the UE device 3250 may obtain condition information about cell reselection through an RRC message. Here, the condition information about cell reselection may be configured based on at least one of a TAC list, a RAC list, and a cell list. The UE device 3250 may receive an RRC message and may switch to an idle state. Then, the UE device 3250 may move from the first cell where it resides to the second cell based on mobility. Here, the UE device 3250 may receive an RRC message including measurement-related information for cell reselection from the second cell. For example, the measurement-related information for cell reselection may include at least one of a TAC list, a RAC list, and a cell ID. Then, the UE device 3250 may verify whether a specific condition is met based on the measurement-related information for cell reselection received from the second cell. Here, as described above, the specific condition may be a condition for determining whether NTN cell measurement and search are required based on at least one of the above-mentioned TAC list, RAC list, and cell ID list. For example, when a specific condition is met based on the information obtained from the first cell, and when residing on the second cell, the UE device 3250 may perform an NTN cell search.

[0390] In addition, for example, the UE device 3250 may obtain reference location information and distance threshold information about each cell in at least one cell through an RRC message. Here, in the case of a TN cell, the reference location information may be a specific point where the TN cell exists. As another example, the reference location information may be a location determined based on the TN cell, and is not limited to a specific embodiment. In the case of an NTN cell, the reference location information may be information derived based on the NTN cell. The UE device 3250 may then derive distance condition information based on the distance threshold information and the reference location information about each cell in at least one cell. Then, as described above, the UE device 3250 may perform a TN cell search based on its current location and distance condition information.

[0391] 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.

[0392] 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.

[0393] 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.

[0397] Industrial Applicability

[0398] The above content can also be applied to other systems.

Claims

1. A method for performing cell reselection by a user equipment (UE) based on a non-terrestrial network (NTN) in a wireless communication system, the method comprising: Obtain cell reselection condition information from a base station; Moving from a first cell to a second cell based on mobility of the UE, and acquiring measurement related information for cell reselection from the second cell; as well as When a specific condition for cell reselection is met based on the cell reselection condition information, an NTN cell search is performed.

2. The method according to claim 1, wherein: The cell reselection condition information is configured based on at least one of a Tracking Area Code (TAC) list, a RAN Area Code (RAC) list, and a cell ID.

3. The method according to claim 1, wherein the cell reselection condition information is transmitted to the UE via a radio resource control (RRC) message.

4. A method for performing cell reselection by a user equipment (UE) based on a non-terrestrial network (NTN) in a wireless communication system, the method comprising: acquiring reference location information and distance threshold information about each of at least one cell from a base station; deriving distance condition information based on the reference location information and the distance threshold information about each of the at least one cell; as well as Based on the current location of the UE and the distance condition information, a terrestrial network (TN) cell search is performed.

5. The method according to claim 1, wherein: The reference location information and the distance threshold information about each of the at least one cell are included in frequency information configured for each of the at least one cell. The method of claim 1 , wherein the at least one cell comprises a TN cell or an NTN cell.

Images