Method and device for configuring multi-connectivity on basis of location in satellite network

Abstract

The present disclosure relates to a 5G or 6G communication system for supporting higher data transmission rates or higher stability beyond a 4G communication system such as LTE. Disclosed are a method and device for adding a secondary node for multi-connectivity in a satellite network (or non-terrestrial network (NTN)).

Description

Method and device for establishing multiple connections based on location in a satellite network

[0001] The present disclosure relates to a method and apparatus for adding a secondary node for multi-connectivity in a satellite network (or non-terrestrial network, NTN).

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

[0003] The 6G communication system, expected to be realized around 2030, will have a maximum transmission speed of terabytes per second (i.e., 1,000 gigabits per second) and a wireless latency of 100 microseconds (μsec). In other words, compared to 5G, the transmission speed in a 6G communication system will be 50 times faster, while the wireless latency will be reduced to one-tenth.

[0004] To achieve these high data rates and ultra-low latency, 6G communication systems are being considered for implementation in the terahertz band (e.g., from 95 gigahertz (GHz) to 3 terahertz (THz)). Compared to the millimeter wave (mmWave) band introduced in 5G, the terahertz band is expected to experience more severe path loss and atmospheric absorption, making it more crucial to ensure signal reach, or coverage, in this band. Key technologies to ensure coverage include radio frequency (RF) components, antennas, new waveforms that offer better coverage than orthogonal frequency division multiplexing (OFDM), beamforming, and multiple antenna transmission technologies such as massive multiple-input and multiple-output (MIMO), full-dimensional MIMO (FD-MIMO), array antennas, and large-scale antennas. In addition, new technologies such as metamaterial-based lenses and antennas, high-dimensional spatial multiplexing using orbital angular momentum (OAM), and reconfigurable intelligent surfaces (RIS) are being discussed to improve the coverage of terahertz band signals.

[0005] In addition, in order to improve frequency efficiency and system network, 6G communication systems are developing full duplex technology that utilizes the same frequency resources for uplink and downlink at the same time; network technology that integrates satellites and high-altitude platform stations (HAPS); network structure innovation technology that supports mobile base stations and enables optimization and automation of network operation; dynamic spectrum sharing technology through collision avoidance based on spectrum usage prediction; AI-based communication technology that utilizes artificial intelligence (AI) from the design stage and internalizes end-to-end AI support functions to realize system optimization; and next-generation distributed computing technology that realizes services with complexity that exceeds the limits of terminal computing capabilities by utilizing ultra-high-performance communication and computing resources (mobile edge computing (MEC), cloud, etc.). In addition, efforts are being made to further strengthen connectivity between devices, further optimize networks, promote softwareization of network entities, and increase the openness of wireless communications through the design of new protocols to be used in 6G communication systems, the implementation of hardware-based security environments, the development of mechanisms for the safe use of data, and the development of technologies for maintaining privacy.

[0006] Research and development of these 6G communication systems are expected to enable a new level of hyper-connected experience through the hyper-connectivity of 6G communication systems, which encompass not only connections between things but also connections between people and things. Specifically, 6G communication systems are expected to enable services such as truly immersive extended reality (XR), high-fidelity mobile holograms, and digital replicas. Furthermore, services such as remote surgery, industrial automation, and emergency response, which are provided through 6G communication systems through enhanced security and reliability, will be applied in diverse fields such as industry, medicine, automobiles, and home appliances.

[0007] Next-generation mobile communication systems are considering Non-Terrestrial Networks (NTNs), which combine satellite communications with mobile communications to expand coverage across the globe. NTNs utilize satellites as relay stations to establish coverage in areas where installing mobile communication base stations is physically or economically impossible.

[0008] It is projected that the number of satellites currently in operation or expected to be operational for NTN will increase to approximately 7,500. Consequently, the number of candidate satellites per terminal could increase from approximately 1-2 to approximately 10 to approximately 100. This could create an environment conducive to improved communication performance by allowing terminals to utilize multiple satellites. However, since satellites move at different speeds based on their varying altitudes and orbits, a communication method that takes this into account will be necessary.

[0009] Accordingly, one purpose of the present disclosure is to propose a method and device for improving direct communication performance with a terminal when a 6G mobile communication system uses a satellite system.

[0010] More specifically, one object of the present disclosure is to propose a method capable of establishing multiple connections to a terminal through multiple satellites, taking into account the mobility of the satellites.

[0011] In a method of a terminal in a communication system according to an example of the present disclosure, the method comprises: receiving, from a base station, a measurement configuration message including configuration information of a measurement report for at least one non-terrestrial network (NTN) cell, the configuration information including information on an event of the measurement report; performing measurement on the at least one NTN cell based on the measurement configuration message; identifying, based on the measurement, an NTN cell satisfying a trigger condition of the event among the at least one NTN cell; and transmitting, to the base station, a measurement report message including a measurement result for the identified NTN cell, wherein the information on the event may include threshold information related to a time during which the at least one NTN cell can serve the terminal.

[0012] In addition, in a method of a base station in a communication system according to an example of the present disclosure, the method includes the steps of: transmitting, to a terminal, a measurement configuration message including configuration information of a measurement report for at least one non-terrestrial network (NTN) cell; and receiving, from the terminal, a measurement report message including a measurement result for an NTN cell among the at least one NTN cell based on the measurement configuration message, wherein the configuration information includes information on an event of the measurement report, and the information on the event may include threshold information related to a time during which the at least one NTN cell can serve the terminal.

[0013] In addition, in a communication system according to an example of the present disclosure, a terminal includes a transceiver; and a control unit for controlling the transceiver to receive, from a base station, a measurement configuration message including configuration information of a measurement report for at least one non-terrestrial network (NTN) cell, wherein the configuration information includes information on an event of the measurement report, perform measurement on the at least one NTN cell based on the measurement configuration message, identify an NTN cell satisfying a trigger condition of the event among the at least one NTN cell based on the measurement, and transmit a measurement report message including a measurement result for the identified NTN cell to the base station, wherein the information on the event may include threshold information related to a time during which the at least one NTN cell can serve the terminal.

[0014] In addition, in a communication system according to an example of the present disclosure, a base station includes a transceiver; and a control unit for controlling the transceiver to transmit a measurement configuration message including configuration information of a measurement report for at least one non-terrestrial network (NTN) cell to a terminal, and for controlling the transceiver to receive, from the terminal, a measurement report message including a measurement result for an NTN cell among the at least one NTN cell based on the measurement configuration message, wherein the configuration information includes information on an event of the measurement report, and the information on the event may include threshold information related to a time during which the at least one NTN cell can serve the terminal.

[0015] According to the present disclosure, there is an effect that an efficient measurement reporting procedure can be performed by considering the mobility of satellites for measurement reporting required for multi-connection setup.

[0016] Additionally, according to one example of the present disclosure, the terminal can reduce power consumption and resource consumption by performing appropriate measurements and measurement reports, and can prevent ping-pong effects due to satellite mobility in connection establishment.

[0017] In addition, according to one example of the present disclosure, when reporting additional information for establishing multiple connections, there is an effect of reducing the overhead of measurement reporting by taking into account NTNs with limited wireless resources.

[0018] FIG. 1 is a diagram illustrating the structure of an LTE system according to an example of the present disclosure.

[0019] FIG. 2 is a diagram illustrating a wireless protocol structure in an LTE system according to an example of the present disclosure.

[0020] FIG. 3 is a diagram illustrating the structure of a next-generation mobile communication system according to an example of the present disclosure.

[0021] FIG. 4 is a diagram illustrating a wireless protocol structure of a next-generation mobile communication system according to an example of the present disclosure.

[0022] FIG. 5a is a diagram illustrating an example of a pseudo-earth-fixed cell being formed in an NTN according to the present disclosure.

[0023] FIG. 5b is a diagram illustrating an example of forming a geomobile cell in an NTN according to the present disclosure.

[0024] FIG. 6a is a diagram for explaining throughput performance in a direct communication situation between an NTN satellite and a handheld UE according to the present disclosure.

[0025] FIG. 6b is a diagram for explaining LOS (line of sight) / NLOS (non-LOS) performance in a direct communication situation between an NTN satellite and a Handheld UE according to the present disclosure.

[0026] FIG. 7 is a diagram comparing signal strength according to the location of a terminal within a cell in an NTN according to an example of the present disclosure.

[0027] FIG. 8 is a flowchart for explaining a measurement reporting operation of a terminal according to an example of the present disclosure.

[0028] FIG. 9 is a diagram illustrating a first example of an event of a measurement report according to an example of the present disclosure.

[0029] FIG. 10 is a diagram illustrating a second example of an event of a measurement report according to an example of the present disclosure.

[0030] FIG. 11 is a diagram illustrating a third example of an event of a measurement report according to an example of the present disclosure.

[0031] FIG. 12 is a diagram illustrating a fourth example of an event of a measurement report according to an example of the present disclosure.

[0032] FIG. 13 is a flowchart for explaining a measurement setting operation of a base station according to an example of the present disclosure.

[0033] FIG. 14 is a flowchart illustrating a procedure for setting up multiple connections according to an example of the present disclosure.

[0034] FIG. 15a is a diagram for explaining a method for configuring terminal location information into GPS coordinates according to an example of the present disclosure.

[0035] FIG. 15b is a diagram for explaining a method of configuring terminal location information into GPS coordinates according to an example of the present disclosure.

[0036] FIG. 15c is a diagram illustrating a method for configuring terminal location information into a grid-based index according to an example of the present disclosure.

[0037] FIG. 16 is a drawing for comparing and explaining a method of transmitting terminal location information according to an example of the present disclosure.

[0038] FIG. 17 is a flowchart illustrating a procedure for setting up multiple connections based on terminal location information according to an example of the present disclosure.

[0039] FIG. 18 is a diagram illustrating an example of a measurement setting message according to an example of the present disclosure.

[0040] FIG. 19 is a diagram illustrating an example of a measurement report message according to an example of the present disclosure.

[0041] FIG. 20 is a block diagram illustrating the structure of a terminal according to one embodiment of the present disclosure.

[0042] FIG. 21 is a block diagram showing the structure of a base station according to one embodiment of the present disclosure.

[0043] The operating principles of the present invention will be described in detail below with reference to the attached drawings. In the following description of the present invention, detailed descriptions of known functions or components will be omitted if they are deemed to unnecessarily obscure the gist of the invention. Furthermore, the terms described below are defined based on their functions in the present invention and may vary depending on the intentions or practices of the user or operator. Therefore, their definitions should be based on the overall content of this specification.

[0044] In the following description of the present invention, detailed descriptions of known functions or configurations will be omitted if they are deemed to unnecessarily obscure the gist of the present invention. Hereinafter, embodiments of the present invention will be described with reference to the attached drawings.

[0045] The terms used in the following description to identify connection nodes, terms referring to messages, terms referring to interfaces between connection nodes, and terms referring to various identification information are provided for convenience of explanation. Therefore, the present invention is not limited to the terms described below, and other terms that refer to objects with equivalent technical meanings may be used.

[0046] For convenience of explanation, the present invention uses terms and names defined in the 1gPP LTE (1st Generation Partnership Project Long Term Evolution) standard. However, the present invention is not limited to these terms and names and can be equally applied to systems conforming to other standards. In the present invention, the term "eNB" may be used interchangeably with "gNB" for convenience of explanation. In other words, a base station described as an eNB may also represent a gNB.

[0047] FIG. 1 is a diagram illustrating the structure of an LTE system according to one embodiment of the present disclosure.

[0048] Referring to FIG. 1, as illustrated, the wireless access network of the LTE system is composed of next-generation base stations (Evolved Node Bs, hereinafter ENBs, Node Bs or base stations) (1-05, 1-10, 1-15, 1-20), MMEs (1-25, mobility management entity) and S-GWs (1-30, Serving-Gateway). User equipment (UEs, hereinafter UEs or terminals) (1-35) access external networks through ENBs (1-05 to 1-20) and S-GWs (1-30).

[0049] In Fig. 1, ENBs (1-05 to 1-20) correspond to the existing Node B of the UMTS (universal mobile telecommunication system) system. ENBs are connected to UEs (1-35) via a wireless channel and perform a more complex role than the existing Node B. In the LTE system, all user traffic, including real-time services such as VoIP (Voice over IP) via the Internet Protocol, is serviced through a shared channel. Therefore, a device that collects status information such as the buffer status of UEs, available transmission power status, and channel status and performs scheduling is required, and ENBs (1-05 to 1-20) are in charge of this. One ENB typically controls multiple cells. For example, in order to implement a transmission speed of 100 Mbps, the LTE system uses, for example, orthogonal frequency division multiplexing (OFDM) as a wireless access technology in a 20 MHz bandwidth. In addition, an adaptive modulation and coding (AMC) method is applied, which determines the modulation scheme and channel coding rate according to the channel status of the terminal.

[0050] S-GW (1-30) is a device that provides data bearers and creates or removes data bearers under the control of MME (1-25).

[0051] MME is a device that is responsible for various control functions as well as mobility management functions for terminals and is connected to multiple base stations.

[0052] FIG. 2 is a diagram illustrating a wireless protocol structure in an LTE system according to one embodiment of the present disclosure.

[0053] Referring to Figure 2, the wireless protocol of the LTE system consists of PDCP (packet data convergence protocol 2-05, 2-40), RLC (radio link control 2-10, 2-35), and MAC (medium access control 2-15, 2-30) in the terminal and ENB, respectively. PDCP (packet data convergence protocol) (2-05, 2-40) is responsible for operations such as IP header compression / decompression. The main functions of PDCP are summarized as follows.

[0054] - Header compression and decompression (ROHC only)

[0055] - User data transfer function

[0056] - In-sequence delivery of upper layer PDUs at PDCP re-establishment procedure for RLC AM

[0057] - Order reordering function (For split bearers in DC (only support for RLC AM): PDCP PDU routing for transmission and PDCP PDU reordering for reception)

[0058] - Duplicate detection function (Duplicate detection of lower layer SDUs at PDCP re-establishment procedure for RLC AM)

[0059] - Retransmission function (Retransmission of PDCP SDUs at handover and, for split bearers in DC, of ​​PDCP PDUs at PDCP data-recovery procedure, for RLC AM)

[0060] - Encryption and decryption functions (Ciphering and deciphering)

[0061] - Timer-based SDU discard in uplink.

[0062] Radio link control (RLC) (2-10, 2-35) reconfigures PDCP PDUs (protocol data units) to an appropriate size and performs ARQ operations, etc. The main functions of RLC are summarized as follows.

[0063] - Data transfer function (Transfer of upper layer PDUs)

[0064] - ARQ function (Error Correction through ARQ (only for AM data transfer))

[0065] - Concatenation, segmentation and reassembly of RLC SDUs (only for UM and AM data transfer)

[0066] - Re-segmentation of RLC data PDUs (only for AM data transfer)

[0067] - Reordering of RLC data PDUs (only for UM and AM data transfer)

[0068] - Duplicate detection function (only for UM and AM data transfer)

[0069] - Error detection function (Protocol error detection (only for AM data transfer))

[0070] - RLC SDU discard function (RLC SDU discard (only for UM and AM data transfer))

[0071] - RLC re-establishment function

[0072] MAC (2-15, 2-30) connects to multiple RLC layer devices configured in a single terminal, and multiplexes RLC PDUs into MAC PDUs and demultiplexes RLC PDUs from MAC PDUs. The main functions of MAC are summarized as follows.

[0073] - Mapping function (Mapping between logical channels and transport channels)

[0074] - Multiplexing and demultiplexing function (Multiplexing / demultiplexing of MAC SDUs belonging to one or different logical channels into / from transport blocks (TB) delivered to / from the physical layer on transport channels)

[0075] - Scheduling information reporting function

[0076] - HARQ function (Error correction through HARQ)

[0077] - Priority handling between logical channels of one UE

[0078] - Priority handling between UEs by means of dynamic scheduling

[0079] - MBMS service identification function

[0080] - Transport format selection function

[0081] - Padding function

[0082] The physical layer (2-20, 2-25) performs the operation of channel coding and modulating upper layer data, converting it into OFDM symbols and transmitting it through a wireless channel, or demodulating and channel decoding OFDM symbols received through a wireless channel and transmitting them to the upper layer.

[0083] FIG. 3 is a diagram illustrating the structure of a next-generation mobile communication system according to one embodiment of the present disclosure.

[0084] Referring to FIG. 3, as illustrated, a wireless access network of a next-generation mobile communication system (hereinafter referred to as NR or 2g) is composed of a next-generation base station (new radio Node B, hereinafter referred to as NR gNB or NR base station) (3-10) and an NR CN (3-05, new radio core network). A user terminal (new radio user equipment, hereinafter referred to as NR UE or terminal) (3-15) accesses an external network through the NR gNB (3-10) and the NR CN (3-05).

[0085] In Fig. 3, the NR gNB (3-10) corresponds to the eNB (Evolved Node B) of the existing LTE system. The NR gNB is connected to the NR UE (3-15) via a wireless channel and can provide a service that is superior to the existing Node B. In the next-generation mobile communication system, all user traffic is serviced through a shared channel, so a device that collects status information such as the buffer status of UEs, available transmission power status, and channel status and performs scheduling is required, and the NR NB (3-10) is in charge of this. One NR gNB typically controls multiple cells. In order to implement ultra-high-speed data transmission compared to the current LTE, it can have a bandwidth higher than the existing maximum, and beamforming technology can be additionally grafted using orthogonal frequency division multiplexing (OFDM) as a wireless access technology. In addition, an adaptive modulation and coding (AMC) method is applied, which determines the modulation scheme and channel coding rate according to the channel status of the terminal.

[0086] The NR CN (3-05) performs functions such as mobility support, bearer setup, and QoS configuration. The NR CN is a device responsible for various control functions as well as mobility management for terminals and is connected to multiple base stations. Furthermore, the next-generation mobile communication system can be interoperable with the existing LTE system, and the NR CN is connected to the MME (3-25) via a network interface. The MME is connected to the existing base station, the eNB (3-30).

[0087] FIG. 4 is a diagram illustrating a wireless protocol structure of a next-generation mobile communication system according to one embodiment of the present disclosure.

[0088] Referring to FIG. 4, the wireless protocol of the next-generation mobile communication system consists of NR SDAP (service data adaptation protocol) (4-01, 4-45), NR PDCP (packet data convergence protocol) (4-05, 4-40), NR RLC (radio link control) (4-10, 4-35), and NR MAC (medium access control) (4-15, 4-30) in the terminal and NR base station, respectively.

[0089] Key features of NR SDAP (4-01, 4-45) may include some of the following:

[0090] - Transfer of user plane data

[0091] - Mapping function between QoS flow and data bearer for both DL and UL

[0092] - QoS flow ID marking function for uplink and downlink (marking QoS flow ID in both DL and UL packets)

[0093] - Ability to map relective QoS flow to data bearer for uplink SDAP PDUs (reflective QoS flow to DRB mapping for the UL SDAP PDUs).

[0094] For the above SDAP layer device, the terminal can be configured by RRC message for each PDCP layer device, each bearer, or each logical channel, whether to use the header of the SDAP layer device or whether to use the function of the SDAP layer device, and when the SDAP header is configured, the terminal can be instructed to update or reset the mapping information for the QoS flow and data bearer of the uplink and downlink with the NAS QoS reflection configuration 1-bit indicator (NAS reflective QoS) and the AS QoS reflection configuration 1-bit indicator (AS reflective QoS) of the SDAP header. The SDAP header can include QoS flow ID information indicating QoS. The QoS information can be used as data processing priority, scheduling information, etc. to support a smooth service.

[0095] The main functions of NR PDCP (4-05, 4-40) may include some of the following functions:

[0096] Header compression and decompression (ROHC only)

[0097] - User data transfer function

[0098] - In-sequence delivery of upper layer PDUs

[0099] - Out-of-sequence delivery of upper layer PDUs

[0100] - PDCP PDU reordering for reception

[0101] - Duplicate detection of lower layer SDUs

[0102] - Retransmission function (Retransmission of PDCP SDUs)

[0103] - Encryption and decryption functions (Ciphering and deciphering)

[0104] - Timer-based SDU discard in uplink.

[0105] The reordering function of the NR PDCP device above refers to a function of reordering PDCP PDUs received from a lower layer in order based on the PDCP SN (sequence number), and may include a function of transmitting data to an upper layer in the reordered order, or may include a function of transmitting data directly without considering the order, may include a function of recording lost PDCP PDUs by reordering the order, may include a function of reporting the status of lost PDCP PDUs to the transmitting side, and may include a function of requesting retransmission of lost PDCP PDUs.

[0106] The main functions of NR RLC(4-10, 4-35) may include some of the following functions:

[0107] - Data transfer function (Transfer of upper layer PDUs)

[0108] - In-sequence delivery of upper layer PDUs

[0109] - Out-of-sequence delivery of upper layer PDUs

[0110] - ARQ function (Error Correction through ARQ)

[0111] - Concatenation, segmentation and reassembly of RLC SDUs

[0112] - Re-segmentation of RLC data PDUs

[0113] - Reordering of RLC data PDUs

[0114] - Duplicate detection function

[0115] - Protocol error detection

[0116] - RLC SDU discard function

[0117] - RLC re-establishment function

[0118] The in-sequence delivery function of the NR RLC device above refers to the function of sequentially transmitting RLC SDUs received from a lower layer to an upper layer, and may include a function of reassembling and transmitting RLC SDUs when an RLC SDU is originally received divided into multiple RLC SDUs, may include a function of reordering received RLC PDUs based on RLC SN (sequence number) or PDCP SN (sequence number), may include a function of recording lost RLC PDUs by reordering the sequence, may include a function of reporting the status of lost RLC PDUs to the transmitting side, may include a function of requesting retransmission of lost RLC PDUs, may include a function of sequentially transmitting only RLC SDUs up to the lost RLC SDU to an upper layer when there is a lost RLC SDU, or may include a function of sequentially transmitting all RLC SDUs received before the timer starts when a predetermined timer expires even when there is a lost RLC SDU. Or, even if there are lost RLC SDUs, if a predetermined timer has expired, it may include a function to sequentially deliver all RLC SDUs received up to the upper layer. In addition, the RLC PDUs may be processed in the order they are received (in the order of arrival, regardless of the order of the sequence number) and delivered to the PDCP device out of sequence (out-of-sequence delivery). In the case of segments, the segments stored in the buffer or to be received later may be received, reconstructed into a single complete RLC PDU, processed, and then delivered to the PDCP device.The above NR RLC layer may not include a concatenation function, and the function may be performed in the NR MAC layer or replaced with a multiplexing function of the NR MAC layer.

[0119] The out-of-sequence delivery function of the NR RLC device above refers to the function of directly delivering RLC SDUs received from a lower layer to an upper layer regardless of the order, and may include a function of reassembling and delivering RLC SDUs when an original RLC SDU is received divided into multiple RLC SDUs, and may include a function of storing the RLC SN or PDCP SN of received RLC PDUs and arranging the order to record lost RLC PDUs.

[0120] NR MAC (4-15, 4-30) can be connected to multiple NR RLC layer devices configured in one terminal, and the main functions of NR MAC can include some of the following functions.

[0121] - Mapping function (Mapping between logical channels and transport channels)

[0122] - Multiplexing / demultiplexing of MAC SDUs

[0123] - Scheduling information reporting function

[0124] - HARQ function (Error correction through HARQ)

[0125] - Priority handling between logical channels of one UE

[0126] - Priority handling between UEs by means of dynamic scheduling

[0127] - MBMS service identification function

[0128] - Transport format selection function

[0129] - Padding function

[0130] The NR PHY layer (4-20, 4-25) can perform operations such as channel coding and modulating upper layer data, converting it into OFDM symbols and transmitting it through a wireless channel, or demodulating and channel decoding OFDM symbols received through a wireless channel and transmitting them to a higher layer.

[0131]

[0132] The non-terrestrial network (NTN) applied in the present disclosure refers to a system that utilizes unmanned aerial systems (UAS), including satellites and high altitude platform stations (HAPS), as relay stations or base stations for ground base stations. NTN is a technology that is applied in particular when satellites are used as relay stations to establish a communication area in areas where the installation of base stations for mobile communication is physically or economically impossible. Satellites that can be utilized in such NTN include Geostationary Earth Orbit (GEO), Medium Earth Orbit (MEO), and Low Earth Orbit (LEO), depending on the satellite's altitude. For example, when LEO satellites are used in NTN, a relatively low delay time can be guaranteed due to the correlation between the satellite's altitude and the delay time.

[0133] Meanwhile, in NR (new radio) NTN, the method of operating satellite cells is classified into 1) earth fixed cell, 2) quasi-earth fixed cell, and 3) earth moving cell.

[0134] First, an earth-fixed cell is a method of forming a stationary satellite cell in a specific area via satellite, with an orbital period identical to the Earth's rotational period. Earth-fixed cells can be implemented using GEO satellites.

[0135] Quasi-earth fixed cells and earth moving cells are methods of forming satellite cells in satellites where the satellite's orbital period and the Earth's rotational period are not the same, and can be implemented through satellites such as MEO / LEO. In the case of a quasi-earth fixed cell, the satellite's beam antenna is rotated (beam steering) to form a cell in a fixed area for a certain period of time, and in the case of an earth moving cell, the satellite's beam antenna that forms the cell is implemented to orbit the Earth while maintaining a constant angle of the beam shining on the Earth's surface. Unlike GEO satellites with earth fixed cells that do not move relative to the Earth's surface and can form cells in a certain area 24 hours a day, LEO and MEO satellites move relative to the Earth's surface, so a single satellite cannot continuously form a cell in a certain area.

[0136] FIG. 5a is a drawing illustrating an example of forming a pseudo-earth-stationary cell in an NTN according to the present disclosure, and FIG. 5b is a drawing illustrating an example of forming an earth-moving cell in an NTN according to the present disclosure.

[0137] More specifically, referring to FIG. 5A, a satellite (NTN vehicle, S1) can move from time point t1 to time point t2, as illustrated. Depending on the movement direction of the satellite (S1), satellite coverage of 501a can be formed at time point t1, and satellite coverage of 502a can be formed at time point t2. Here, the serving area (satellite coverage) formed by the satellite (S1) is the maximum area in which a terminal on the ground surface can receive communication services from the satellite, and for example, can be defined as an arbitrary area in which the elevation angle, which is the angle between the line of sight of a satellite located at a predetermined altitude above the ground surface and the ground surface (horizontal line), has a minimum value. At this time, the minimum elevation angle may be set to the minimum angle value at which the satellite can serve a terminal located on the surface of the earth with a predetermined quality or higher, and when the elevation angle is at the maximum value, it may be expected that the communication quality within the serving area will be the best.

[0138] Meanwhile, as illustrated in FIG. 5A, a satellite (S1) can form a cell (500) in a fixed area for a certain period of time by rotating the satellite beam antenna (beam steering), and a terminal located within the serving area of ​​the satellite cell formed in this manner can receive service from the satellite (S1) through the cell (500) from time t1 to time t2. Thereafter, when the terminal is located at a position greater than the maximum antenna rotation angle of S1 due to the movement of the satellite S1, the terminal may be served by another satellite in the vicinity. In this manner, in the case of a quasi-earth fixed cell, after a certain period of time, the next quasi-earth fixed cell sequentially services the area for the corresponding point.

[0139] Referring to FIG. 5b, in the case of an earth moving cell, the angle of the beam that the satellite (S2) illuminates the Earth's surface remains constant as it orbits the Earth, so that the serving area is formed on the Earth's surface at time t1, as shown at 501b, but moves with respect to the Earth's surface at time t2, as shown at 502b. As described above, in the case of an earth moving cell, since the beam antenna of the satellite forming the cell moves while maintaining the angle of the beam that illuminates the Earth's surface constant, a specific beam area moves as shown at 51 to 52 over time.

[0140] As described above, since satellites are constantly moving, the satellites that make up a cell change at most every 256 seconds for quasi-earth fixed cells and at most every 22 seconds for terminals at the cell edge for earth moving cells. In other words, a terminal that is in an RRC (radio resource control) connected state to a specific satellite needs to perform a handover to another satellite at a predetermined interval in order to receive appropriate services from the satellite, and a terminal that is in an RRC idle / inactive state needs to perform cell selection and reselection operations.

[0141] In addition, since the time at which a terminal can connect to a satellite varies depending on whether the terminal is located at the edge or the center of the cell formed by the satellite, when selecting an appropriate satellite to serve the terminal, it is necessary to consider not only the mobility of the satellite, but also the orbit of the satellite and the location of the terminal. This will be described later with reference to FIG. 7. In addition, for the convenience of explanation, the terms NTN cell, satellite cell, NTN satellite, satellite, etc. will be used interchangeably to describe a satellite operating in NTN.

[0142] Meanwhile, in situations of direct communication between a satellite and a terminal, the characteristics of NTN itself also need to be considered.

[0143] FIG. 6a is a diagram for explaining throughput performance in a direct communication situation between an NTN satellite and a handheld UE according to the present disclosure, and FIG. 6b is a diagram for explaining LOS (line of sight) / NLOS (non-LOS) performance in a direct communication situation between an NTN satellite and a handheld UE according to the present disclosure.

[0144] In a LEO-based communication situation, considering direct communication between an NTN satellite and a terminal, the total throughput is approximately 5% of that of a Very Small Aperture Terminal (VSAT), as shown in Fig. 6a. VSAT and handheld UE have significantly different antenna gain performances and different usable frequency bands, resulting in a significant difference in total throughput performance. This reduction in throughput performance of handheld UEs is due to the lower signal-to-interference plus noise ratio (SINR) caused by inter-cell and inter-satellite interference, and the use of frequency division to resolve such interference issues. In addition, handheld UEs use circular polarization, making it difficult to distinguish between Left Hand Circular Polarization (LHCP) and Right Hand Circular Polarization (RHCP), resulting in a polarization loss of approximately 3 dB. In addition, if the directions of the satellite and the handheld UE are not aligned, there is an additional significant performance degradation, which reduces throughput performance.

[0145] Considering direct communication between NTN satellites and terminals, as shown in Fig. 6b, we can also see that the communication performance difference increases depending on whether the communication connection situation is Line of Sight (LOS) or Non-Line of Sight (NLOS). For example, in an NLOS situation, terminal performance, throughput, is reduced to less than 1 / 10 of that in LOS, because shadow fading and cluster loss increase by approximately 25 dB. According to data that has already been modeled regarding the probability of NLOS phenomenon occurring, the index value for the possibility of LOS is only about 40% (for example, in a situation where the elevation angle is 30°) assuming a dense urban scenario.

[0146] As described above in Figures 6a and 6b, considering the characteristics of NTN itself, direct communication between a satellite and a terminal can be seen to have poor connectivity. Furthermore, if satellites with various altitudes are applied for direct communication with a terminal, long Round Trip Time (RTT) may be a problem in GEO, which is very far from the ground, and in LEO, the problem of communication performance degradation, such as the transition from LOS to NLOS due to the fast movement speed, may occur. As a solution to this problem, the present disclosure proposes a multi-connection configuration method in which a terminal is connected to multiple satellites.

[0147] When multiple connections are established for a terminal via multiple satellites, the base station needs information to determine whether the satellite to which the connection is being added is suitable for serving the terminal. For example, the terminal can transmit the signal strength values ​​measured for other surrounding satellite cells as a measurement report to the base station currently serving the terminal (e.g., an NTN satellite). At this time, the signal strength according to the terminal's location within the cell formed by the satellite must be considered.

[0148] FIG. 7 is a diagram comparing signal strength according to the location of a terminal within a cell in an NTN according to an example of the present disclosure.

[0149] As shown in (a) of Fig. 7, in the case of a terrestrial network, the difference in signal reception strength (e.g., reference signal received power, RSRP) can significantly vary depending on whether the terminal is located at the edge or center of the cell.

[0150] In contrast, referring to Figure 7(b), the signal strength difference is relatively small in non-terrestrial networks. For example, the signal strength difference between the center and edge of the cell is approximately 1 dB in GEO and 9.8 dB in LEO at 600 km. This means that the signal strength difference is not significant, especially in the cell edge region where the beams between two satellites overlap, compared to the center of the cell.

[0151] That is, if measurement reports are performed by applying existing measurement events based on signal strength (e.g., A1 event, B1 event, etc.), it may be difficult for the current serving base station to distinguish which satellite is more suitable for supporting the terminal. For example, even in the edge area of ​​the cell, the signal strength is sufficiently strong, so even if the satellite moves away from the terminal and does not guarantee sufficient time to serve the terminal, the base station sets the terminal to connect to the satellite based on the signal strength, which may frequently result in ping-pong phenomenon between cells. In addition, the terminal performs unnecessary or excessively frequent measurement event triggering / reporting operations without distinguishing between satellites moving toward the terminal and satellites moving away from the terminal, which may be a burden, especially in NTNs with limited radio resources. Therefore, in the present disclosure, we propose a method for supporting multiple connections based on location, so as to prevent robustness degradation due to the ping-pong effect between cells when performing multiple connections via satellites.

[0152] More specifically, in the present disclosure, when applying measurement event-based measurement reporting when establishing multiple connections of a satellite, a location-based triggering condition that takes into account the characteristics of NTN is added to the existing signal strength-based measurement report triggering conditions (e.g., A1 event, B1 event) so that the measurement report can be triggered only in appropriate situations. As described above, since the time that an NTN cell can serve a terminal varies depending on the location of the terminal, the mobility of the NTN cell, and the location (orbit and altitude, etc.) of the NTN cell, the present disclosure proposes a method of additionally reflecting various parameters that can indicate the terminal serving time of the satellite in the triggering conditions of the measurement report so as to support location-based multiple connection establishment.

[0153] For convenience of explanation, the following describes a method for adding a secondary node (SN) under the assumption of DC (dual connectivity) in a multi-connectivity situation. In this case, the base station currently serving the terminal operates as the DC's MN (master node). While it is assumed to be an NTN satellite, it is readily apparent to those skilled in the art that a scenario in which a terrestrial base station operates as the DC's MN is not excluded.

[0154] FIG. 8 is a flowchart for explaining a measurement reporting operation of a terminal according to an example of the present disclosure.

[0155] Referring to FIG. 8, a terminal according to an example of the present disclosure can receive a measurement configuration message including configuration information of a measurement report for at least one NTN cell from a base station (S810).

[0156] A measurement message according to an example of the present disclosure may be transmitted to a terminal via RRC signaling, and the configuration information of the measurement report may include information on an event of the measurement report since the report type is set to event triggered. Here, the information on the event of the measurement report may include, for example, information on a condition for determining a trigger of the event of the measurement report, such as ID (identity) information for identifying each event, and threshold information or time information for determining the trigger condition of the event. In addition, the threshold information may include, for example, a threshold for a signal strength value, and in particular, in an example according to the present disclosure, the threshold information may include threshold information related to a time during which at least one NTN cell around the terminal can serve the terminal. More specific examples of threshold information will be described later with reference to FIGS. 9 to 12.

[0157] A terminal that has received a measurement setup message can perform measurement on at least one NTN cell based on the measurement setup message (S820).

[0158] Here, information about at least one NTN cell to be measured may be provided via the measurement configuration message (e.g., measobject). Furthermore, a terminal according to an example of the present disclosure may obtain information necessary for the measurement via system information periodically broadcast by a base station. For example, the system information may include at least one of cell identification information that can identify an NTN satellite that may be measured, information about the orbit of the satellite, or information about the altitude of the satellite.

[0159] Thereafter, the terminal can identify, based on the measurement, an NTN cell that satisfies the trigger condition of the measurement event among at least one NTN cell (S830).

[0160] That is, a terminal according to an example of the present disclosure can identify an NTN cell corresponding to a measurement result value that satisfies a trigger condition of a measurement event, based on a measurement result for at least one NTN cell.

[0161] And, a measurement report message including the measurement results for the identified NTN cell can be transmitted to the base station (S840).

[0162] In this way, by setting threshold information used to determine the time at which a satellite can serve a terminal based on the location of the terminal and satellite as an event trigger condition of a measurement report, the terminal can perform measurement reporting only when necessary in a situation where additional satellites are connected (e.g., SN addition), thereby reducing frequent or unnecessary measurement reporting and enabling selection of a satellite suitable for serving the terminal.

[0163] Hereinafter, the event configuration of measurement reports will be described in more detail so as to support measurement reports based on satellite mobility and terminal location. In this disclosure, the N1 event is defined as threshold information for SN addition based on measurement report events. The N1 event is a condition that is additionally considered separately from the existing triggering conditions such as the A1 event and B1 event for SN addition, and can be defined as an event value regarding the time during which the satellite can serve the terminal. In calculating a value related to the time during which the satellite can serve the terminal, various information such as the satellite's orbit, velocity, and terminal's position are required. However, accurately calculating the service connection possible time or service connection possible distance based on this can be a great burden on the terminal's computational capability. Therefore, in this disclosure, a method for applying a more simplified calculation method using some information on the satellite orbit and satellite velocity will be described using FIGS. 9 to 12.

[0164] FIG. 9 is a diagram illustrating a first example of an event of a measurement report according to an example of the present disclosure.

[0165] Referring to FIG. 9, threshold information related to a trigger condition of a measurement report event according to an example of the present disclosure is a threshold for the service time of an NTN cell. time) can be indicated. Here, the service time can be defined, for example, by an estimated value (t'-service) for the time when the elevation angle of the NTN cell with respect to the terminal satisfies the minimum elevation angle. For example, if the time when the NTN cell approaches the terminal and its elevation angle starts to become larger than the minimum elevation angle is t1, and the time when the NTN cell starts to move away from the terminal and its elevation angle starts to become smaller than the minimum elevation angle is t2, then t'-service can be defined as the value of t2-t1. That is, the time when the NTN cell can serve the terminal can be confirmed based on t'-service.

[0166] Based on this, the t'-service calculated by the terminal is a threshold for service time (Thresh time ) is greater than or equal to, the terminal according to an example of the present disclosure may determine that the event trigger condition of the measurement report is satisfied and transmit the measurement report for the corresponding NTN cell to the base station.

[0167] - triggering condition: t'-service ≥ Thresh time

[0168] FIG. 10 is a diagram illustrating a second example of an event of a measurement report according to an example of the present disclosure.

[0169] Referring to FIG. 10, threshold information related to a trigger condition of a measurement report event according to an example of the present disclosure is the degree of elevation change of the NTN cell ( ) for threshold( ) and can indicate the minimum elevation angle related to the degree of the elevation angle change.

[0170] Here, the degree of elevation change is related to the direction in which the NTN cell moves relative to the terminal. For example, if the NTN cell moves in a direction closer to the terminal, the degree of elevation change is a value greater than or equal to 0 ( ), if the NTN cell moves away from the terminal, a value less than 0 ( ) is derived. In this way, when the NTN cell moves away from the terminal ( ), the measurement report can be set to be triggered only when the altitude is above a certain angle (i.e., when the service can be provided for a sufficient amount of time), because the time that the terminal can be served is relatively short or the terminal will soon leave the service area that can serve the terminal. However, in the present embodiment, the altitude change degree is a value greater than or equal to 0 ( ) can be set to trigger a measurement report.

[0171] Meanwhile, when the satellite orbit of the NTN cell passes vertically above the terminal or moves far away, the absolute value of the elevation angle change of the NTN cell may vary over a given period of time. For example, when the satellite orbit of the NTN cell passes vertically above the terminal, the absolute value of the elevation angle change of the NTN cell may be greater than the threshold value ( ) may be greater than or equal to the threshold value. In contrast, if the satellite orbit of the NTN cell moves far away from the terminal, the absolute value of the elevation angle change of the NTN cell over a given period of time may be greater than or equal to the threshold value ( ) may be less than.

[0172] At this time, the minimum elevation angle, which is a trigger condition for the measurement report event, may be applied differently depending on the absolute value of the elevation angle change degree of the NTN cell.

[0173] More specifically, as shown in FIG. 10, when the NTN cell (10a) passes vertically above the terminal, the elevation angle of the NTN cell (10a) starts from the minimum value and reaches a relatively large elevation angle value (for example, up to 90°), so the change value of the elevation angle is large. ) That is, in the case of NTN cell (10a), since the service time that can serve the terminal by moving vertically above the terminal is relatively long, the elevation angle of the NTN cell (10a) is the minimum elevation angle value. If it is determined that the case is greater than this, the terminal can determine that an event in the measurement report has been triggered.

[0174] In contrast, when the orbit of the NTN cell (10b) is relatively far from the terminal, even if it gets as close as possible to the terminal, the maximum elevation angle for the terminal is reached with a relatively small value, so the change in the elevation angle is also relatively smaller than that of the NTN cell (10a). ). In this case, the elevation angle of the corresponding NTN cell (10b) is the minimum elevation angle value. If it is determined that the case is greater than , the terminal can determine that the event of the measurement report has been triggered. However, since the NTN cell (10b) has a shorter service time for the terminal than the NTN cell (10a) and cannot provide service at a larger elevation angle, the minimum elevation angle size can be set to a larger value than the NTN cell (10a). )

[0175] - triggering condition

[0176] If

[0177] If and

[0178] If and

[0179]

[0180] FIG. 11 is a diagram illustrating a third example of an event of a measurement report according to an example of the present disclosure.

[0181] Referring to FIG. 11, threshold information related to a trigger condition of a measurement report event according to an example of the present disclosure is a threshold value of the distance that an NTN cell has moved within a preset serving area. ) can be directed.

[0182] Here, the preset serving area refers to the maximum area in which a terminal on the ground surface can receive communication services from an NTN cell, as described above in FIG. 5A, and can be determined based on the terminal's location on the ground surface, the altitude of the NTN cell, and the minimum elevation angle according to the positional relationship between the NTN cell and the terminal. In this case, when defining the preset serving area on the ground surface where the terminal is located, it can be defined as a circle having a predetermined cell radius centered on the point where the terminal is located.

[0183] For example, assuming that an NTN cell moves almost parallel to the ground surface where the terminal is located, and implementing the path that the NTN cell moves on the ground surface, the distance that the NTN cell moves in the preset serving area is calculated by using the points where the curve corresponding to the path passes through the serving area defined as a circle based on the terminal. ) can be calculated. For example, as shown in Fig. 11, the straight-line distance connecting the points where the NTN cell's path intersects the terminal-based circle can be calculated as the distance the NTN cell has moved within the preset serving area.

[0184] A terminal according to an example of the present disclosure determines the time at which an NTN cell can serve the terminal based on the straight-line distance calculated in this way, and the straight-line distance is a specific ratio of the cell diameter ( ) above, it can be determined that the event of the measurement report has been triggered.

[0185] In this example, a simplified method using two points where the NTN cell passes through the terminal-based circle is used to calculate the distance that the NTN cell moves within the terminal-based circle, but a method using more points is also possible.

[0186] - Triggering condition:

[0187] ,

[0188]

[0189] FIG. 12 is a diagram illustrating a fourth example of an event of a measurement report according to an example of the present disclosure.

[0190] Referring to FIG. 12, threshold information related to a trigger condition of a measurement report event according to an example of the present disclosure is a threshold for an angle at which an NTN cell enters a preset serving area toward a terminal. ) can be directed.

[0191] Here, the preset serving area can be determined based on the terminal location on the ground surface, the altitude of the NTN cell, and the minimum elevation angle according to the positional relationship between the NTN cell and the terminal, as described above in FIG. 11, and can be defined as a circle having a predetermined cell radius centered on the point where the terminal is located, as shown in FIG. 12.

[0192] As in Fig. 11, assuming that the NTN cell moves almost parallel to the ground surface where the terminal is located, and implementing the path of movement of the NTN cell on the ground surface, a point (12) where the NTN cell enters the preset serving area toward the terminal is defined, and the angle formed by the tangent line (12a) at that point (12) and the direction (12b, 12c) in which the NTN cell moves at that point is called the penetration angle. can be defined as follows.

[0193] At this time, the terminal according to the example of the present disclosure, Based on the value of , the time when the NTN cell can serve the terminal is determined. For example, Depending on the value of , the satellite passes vertically above the terminal (e.g., ) to ensure a longer service time for the terminal, or, alternatively, by passing through the terminal-based circle (e.g., ) can determine whether the service time for the terminal is very short. Accordingly, the terminal, The value of the above set threshold ( ) above, it can be determined that the trigger condition of the measurement report event is satisfied.

[0194] - Triggering condition:

[0195] In FIGS. 9 through 12, four examples of event (N1 event) information of various measurement reports that predict the time at which an NTN cell can serve a terminal are provided for location-based SN addition. While each of the four examples can be configured separately, a base station according to an example of the present disclosure can also configure a measurement report to trigger a measurement report when at least one of the four examples is satisfied together.

[0196] FIG. 13 is a flowchart for explaining a measurement setting operation of a base station according to an example of the present disclosure.

[0197] In this drawing, descriptions that overlap with the above descriptions are omitted or briefly described.

[0198] A base station according to an example of the present disclosure can transmit a measurement configuration message including configuration information of a measurement report for at least one NTN cell to a terminal (S1310).

[0199] At this time, the measurement configuration message may be transmitted via an RRC message as described above in FIG. 8, and may include information on an event of a measurement report. The information on the event of the measurement report here may include information on at least one of the N1 event values ​​described above in FIGS. 9 to 12. In an example of the present disclosure, when a base station determines a multi-connection configuration for a serving terminal in consideration of communication service support, congestion situation, load situation, etc., the base station may select N1 event values ​​appropriate to the situation and set them to the terminal.

[0200] Based on the above measurement setup message, a measurement report message including measurement results for an NTN cell can be received from the terminal (S1320).

[0201] The measurement report message may include information about the terminal's signal strength measurements for the NTN cell. Furthermore, as described below, the measurement report message may include location information related to the terminal, depending on how the base station configures the measurement configuration message.

[0202] A base station according to an example of the present disclosure can determine whether to establish multiple connections by adding the corresponding NTN cell to the terminal based on a measurement report message of the terminal.

[0203] The procedure related to this will be explained with reference to Fig. 14.

[0204] FIG. 14 is a flowchart illustrating a procedure for setting up multiple connections according to an example of the present disclosure.

[0205] Referring to FIG. 14, a terminal (1401) according to an example of the present disclosure is connected to a base station (1402) in an RRC connection state. The base station (1402) can transmit a measurement configuration message to the terminal (1401) to configure measurement and measurement reporting for surrounding NTN cells (S1410).

[0206] The measurement configuration message herein may include information on a predetermined event value, i.e., an N1 event, so as to trigger a measurement report for an NTN cell sufficient to serve the terminal based on the positional relationship between the terminal (1401) and the NTN cell as described above. The information on the N1 event may include at least one of the thresholds described above with reference to FIGS. 9 to 12. In addition, although not illustrated in the drawing, in the measurement configuration for general SN addition, a configuration for an event value (A1 event, B1 event, etc.) related to signal strength may also be included in the measurement configuration message.

[0207] The terminal (1401) can perform measurements on at least one NTN cell located in the vicinity based on a measurement configuration message (S1420). The base station (1402) can periodically broadcast information on each NTN cell, such as ephemeris data such as NTN cell identification information or orbit information, through system information (e.g., SIB 19). The terminal (1401) can perform the measurement operation using the information included in the system information. In addition, the terminal (1401) can determine whether an N1 event is triggered based on the measurement result values.

[0208] If it is determined that an N1 event has been triggered, the terminal (1401) can transmit information about the NTN cell having the measurement result value for which the N1 event has been triggered to the base station (1402) through a measurement report message (S1430).

[0209] The base station (1402) may determine to add a connection of an NTN cell (1403) to the terminal (1401) based on a measurement report message from the terminal (1401) (S1440). At this time, if a measurement report message including information on multiple NTN cells is received, the base station (1402) may, for example, select the NTN cell with the best signal strength value among the multiple NTN cells as the cell to be added to the terminal (1401).

[0210] The base station (1402) can transmit an SN addition request message including information about the terminal (1401) to the selected NTN cell (1403) (S1450), and when the NTN cell (1403) approves the request, the base station (1402) can transmit an SN addition ACK message including predetermined information required for the terminal (1401) to connect to the NTN cell (1403) (S1460).

[0211] The base station (1402) can transmit information conveyed as an SN addition ACK message to the terminal (1401) through an RRC message (e.g., RRCconnection Reconfiguration) (S1470), and the terminal (1401) can transmit a response thereto to the base station (1402) (e.g., RRCconnection reconfiguration complete) (S1480).

[0212] Although not shown in the drawing, when the terminal performs random access to the NTN cell, the DC between the base station and the target NTN cell is set for the terminal.

[0213] According to the embodiments of the present disclosure described above, frequent and inefficient measurement events that may occur in NTNs can be triggered only when necessary, the ping-pong effect due to satellite mobility when supporting connection can be prevented, and since the terminal triggers measurement reports only when necessary, there is an effect of reducing power consumption due to measurements and resource consumption due to unnecessary measurement reports. Furthermore, due to information-based SN addition, it is possible to select a satellite suitable for serving the terminal from among the increasing number of satellite candidates.

[0214] As mentioned in Fig. 13, when transmitting a measurement report for SN addition, the terminal can transmit additional information so that the base station can perform an appropriate SN addition. In this case, the present disclosure proposes that the additional information transmitted by the terminal include the terminal's location information. When the base station additionally receives the terminal's location information, it can accurately calculate the actual service receiving time for each terminal along with the satellite orbit, which has the effect of selecting a more appropriate NTN cell for SN addition. Based on this, the present disclosure proposes a method for reducing overhead when transmitting location information via the terminal uplink, considering the NTN with limited radio resources. The following description assumes that the terminal additionally includes the terminal's location information when transmitting the measurement report message; however, this procedure may also be performed through a separate procedure from the measurement report procedure. For example, the base station may, if necessary, request the terminal to transmit location information, and the terminal location information reporting procedure may of course be triggered accordingly.

[0215] In this disclosure, we propose two methods for transmitting location information while reducing overhead.

[0216] The first method involves transmitting terminal location information using GPS (global positioning system) coordinates. Figures 15a and 15b are diagrams illustrating a method for configuring terminal location information using GPS coordinates according to an example of the present disclosure.

[0217] In the case of GPS coordinates, the resolution and accuracy of location information vary depending on the number of decimal points in the GPS coordinates. While GPS coordinates could be transmitted via RRC's commonLocationInformation, the format is somewhat limited, and since it transmits both GPS information and related location information together, a large number of bits must be allocated. Therefore, the existing GPS coordinate transmission method is not suitable for NTNs with limited radio resources. Therefore, the present disclosure proposes a method for transmitting location information using GPS coordinates, while allowing the size of the GPS coordinate information to be flexibly set. For example, a base station can designate and allocate a number of bits for GPS coordinates to a terminal. For example, the base station can configure the number of decimal points of GPS coordinate information bits that the base station wants to receive from the terminal via an RRC message, and the terminal can transmit location information to the base station using the number of bits set accordingly.

[0218] Since the location of the terminal is limited to a given cell range, the base station can sufficiently infer the location of the terminal even if all GPS coordinate information is not transmitted. For example, since the tens digit of the GPS coordinate distinguishes approximately 1000 km, the + / - signs indicating latitude / longitude can be omitted as shown in Fig. 15a, and the hundreds digit of longitude can be omitted (latitude: -90° to 90°, longitude: -180° to 180°). Additionally, information about the sign need only be transmitted near the equator and the prime meridian (where longitude is 0° and 180°), as shown in Fig. 15b. For example, based on a 200 km cell radius, the sign need only be transmitted for latitude / longitude ±0° to 10° and longitude ±170° to 180°. Therefore, according to the present disclosure, the base station can roughly determine the location of the terminal based on GPS coordinate information represented with a relatively small number of bits.

[0219] Second, assuming a grid where the MN cells are expanded into a square, the index where the terminal is located A method for transmitting information about. FIG. 15c is a diagram for explaining a method for configuring terminal location information into a grid-based index according to an example of the present disclosure.

[0220] Referring to Fig. 15c, system information (e.g., SIB 19) transmitted from a base station to a terminal may include information about the center point and radius of the corresponding base station cell. When the terminal provides this information and the grid spacing value through an RRC message from the base station, the terminal can derive the index of the grid to which the terminal belongs. For example, the center point of the cell can be expressed as index = 0, and the range of the index can be expressed as {-maxIndexSize … 0 … maxIndexSize-1}.

[0221] At this time, the method for calculating the terminal index is as follows.

[0222] - UE position

[0223] - Cell center and cell radius

[0224] - Index spacing , column index spacing

[0225] - Row index , column index

[0226] (1) Max row index size , max column index size

[0227] (2) If , then and If , then

[0228] (3) If , then and If , then

[0229] (4) else, and

[0230] According to this example, the terminal can calculate the maxIndexSize through (1) and the terminal index through (4). If the terminal is determined to be outside the cell range, the terminal can determine the index closest to the terminal's location through (2) and (3).

[0231] FIG. 16 is a drawing for comparing and explaining a method of transmitting terminal location information according to an example of the present disclosure.

[0232] The number of bits required for the two location information transmission methods described in FIGS. 15a, 15b, and 15c can be reduced by about 1 to 3 bits if the sign and hundreds digits of GPS coordinates are omitted based on the same resolution, as shown in FIG. 16, and by 1 / 2 to 1 / 3 bits if the grid method is used.

[0233] In the GPS coordinate transmission method, the method of adjusting the resolution of the position is limited to the number of decimal places of the GPS, whereas the grid index transmission method has the advantage of not having restrictions compared to GPS coordinates because the resolution can be adjusted by adjusting the grid spacing. For example, in order to have a resolution of 50 m, in the case of the grid index transmission method, the grid spacing can be set to 50 m without changing the number of bits, but in the case of the GPS coordinate transmission method, the difference is that it must be set to 4 decimal places with a resolution of 10 m.

[0234] Figure 17 is a flowchart illustrating a procedure for establishing multiple connections based on terminal location information according to an example of the present disclosure. In the following, descriptions of Figure 17 that overlap with the operations and features described above in Figure 14 will be omitted or briefly described.

[0235] Referring to FIG. 17, a terminal (1701) according to an example of the present disclosure is connected to a base station (1702) in an RRC connection state. The base station (1702) may transmit a measurement configuration message to the terminal (1701) to configure measurement and measurement reporting for surrounding NTN cells (S1710).

[0236] The measurement configuration message herein may include information about a predetermined event value, i.e., an N1 event, to trigger a measurement report for an NTN cell sufficient to serve the terminal based on the positional relationship between the terminal (1701) and the NTN cell, as described above. The information about the N1 event may include at least one of the threshold values ​​described above in FIGS. 9 to 12.

[0237] The terminal (1701) can perform measurements on at least one NTN cell located in the vicinity based on the measurement setup message (S1720).

[0238] The terminal (1701) can perform measurements based on information about NTN candidate cells and measurement trigger events included in the measurement configuration message, and can utilize information acquired through system information (e.g., SIB 19) for the measurements. In addition, the measurement configuration message according to an example of the present disclosure may include information instructing the terminal (1701) to report location information of the terminal together with the measurement report. For example, information for setting whether to report location information of the terminal based on the cell range of the corresponding base station (1702) based on GPS coordinates or a grid index may additionally be included.

[0239] If the terminal (1701) determines that an N1 event has been triggered based on measurement result values, the terminal (1701) can transmit information about the NTN cell having the measurement result value for which the N1 event has been triggered to the base station (1702) via a measurement report message (S1730). At this time, based on what is set by the base station (1702), the terminal (1701) can report the terminal's location information along with the measurement result value to the base station (1702) based on GPS coordinates or a grid index.

[0240] The base station (1702) can decide to add a connection to the NTN cell (1703) for the terminal (1401) based on the measurement report message from the terminal (1701) (S1740).

[0241] At this time, the base station (1702) can select an NTN cell to which to additionally establish a connection to the terminal (1701) using the location information of the terminal (1701) along with the measurement result. For example, when a measurement report message including information on multiple NTN cells is received from the terminal (1701), the base station (1702) can select, from among the multiple NTN cells, an NTN cell that is most suitable for serving the terminal (1701) considering the location of the terminal.

[0242] The base station (1702) can transmit an SN addition request message including information about the terminal (1701) to the selected NTN cell (1703) (S1750), and when the NTN cell (1703) approves the request of the base station (1702), the terminal (1701) can transmit an SN addition ACK message including predetermined information necessary for connecting to the corresponding NTN cell (1703) to the base station (1702) (S1760).

[0243] The base station (1702) can transmit information transmitted as an SN addition ACK message to the terminal (1701) through an RRCconnection Reconfiguration message (S1770), and the terminal (1701) can transmit an RRCconnection reconfiguration complete message to the base station (1702) in response thereto (S1780).

[0244] After the terminal successfully completes random access to the NTN cell, DC is established between the base station and the NTN cell.

[0245] According to the present disclosure, a terminal can provide information on a highly accurate terminal location to a base station with a minimum information size without excessive resource consumption or overhead, and the base station can support multiple connections by selecting an NTN cell that can serve the terminal as the most suitable cell based on the terminal location.

[0246] FIG. 18 is a diagram illustrating an example of a measurement setting message according to an example of the present disclosure, and FIG. 19 is a diagram illustrating an example of a measurement report message according to an example of the present disclosure.

[0247] According to an example of the present disclosure, a measurement configuration message transmitted from a base station to a terminal may include information about each event in an information field as illustrated in FIG. 18 when setting the measurement report to be reported as an “eventtriggered” type. As described above, the measurement configuration message may include information about an N1 event proposed in the present disclosure in addition to information about an existing signal strength-related event, or optionally in addition to an existing signal strength-related event.

[0248] Information about an N1 event, in addition to information about the ID of the event and information about the time for triggering, may include, as measurement types, thresholds for various parameters that can indicate the time for which the NTN cell can serve the terminal. For example, the threshold for the service time (approx-Tservice) of the NTN cell described in FIG. 9, the threshold related to the degree of elevation angle change (deltaElevationAngle) of the NTN cell described in FIG. 10, the threshold for the terminal serving distance (distanceUEcell) of the NTN cell described in FIG. 11, and the threshold for the entry angle (penetrationAngle) into the terminal serving area of ​​the NTN cell described in FIG. 12 may be included as measurement types.

[0249] Additionally, when a base station according to an example of the present disclosure is additionally set to report location information of a terminal, the setting for the report type may instruct the terminal location information to be reported as either GPS coordinates or a grid index.

[0250] Additionally, the terminal may include various information in the measurement report message, as illustrated in FIG. 19, in response to the measurement settings of the base station. The measurement report message may include information indicating which NTN cell the measurement result is for, measurement result information for the NTN cell, and, if location information reporting is set, GPS coordinates or grid indexes as terminal location information, depending on the setting type.

[0251] FIG. 20 is a block diagram illustrating the structure of a terminal according to one embodiment of the present disclosure.

[0252] Referring to FIG. 20, a terminal according to one embodiment of the present disclosure may include an RF (Radio Frequency) processing unit (20-10), a baseband processing unit (20-20), a storage unit (20-30), and a control unit (20-40).

[0253] The RF processing unit (20-10) performs functions for transmitting and receiving signals through a wireless channel, such as signal band conversion and amplification. That is, the RF processing unit (20-10) up-converts the baseband signal provided from the baseband processing unit (20-20) into an RF band signal and transmits it through an antenna, and down-converts the RF band signal received through the antenna into a baseband signal. For example, the RF processing unit (20-10) may include a transmission filter, a reception filter, an amplifier, a mixer, an oscillator, a digital to analog convertor (DAC), an analog to digital convertor (ADC), etc. In the drawing, only one antenna is illustrated, but the terminal may be equipped with multiple antennas. In addition, the RF processing unit (20-10) may include multiple RF chains. Furthermore, the RF processing unit (20-10) may perform beamforming. For the above beamforming, the RF processing unit (20-10) can adjust the phase and size of each signal transmitted and received through multiple antennas or antenna elements. In addition, the RF processing unit can perform MIMO and receive multiple layers when performing the MIMO operation.

[0254] The baseband processing unit (20-20) above performs a conversion function between a baseband signal and a bit stream according to the physical layer specifications of the system. For example, when transmitting data, the baseband processing unit (20-20) generates complex symbols by encoding and modulating a transmission bit stream. In addition, when receiving data, the baseband processing unit (20-20) restores the reception bit stream by demodulating and decoding the baseband signal provided from the RF processing unit (20-10). For example, in the case of following the OFDM (orthogonal frequency division multiplexing) method, when transmitting data, the baseband processing unit (20-20) generates complex symbols by encoding and modulating a transmission bit stream, maps the complex symbols to subcarriers, and then configures OFDM symbols through an inverse fast Fourier transform (IFFT) operation and a cyclic prefix (CP) insertion. In addition, when receiving data, the baseband processing unit (20-20) divides the baseband signal provided from the RF processing unit (20-10) into OFDM symbol units, restores signals mapped to subcarriers through FFT (fast Fourier transform), and then restores the received bit string through demodulation and decoding.

[0255] The baseband processing unit (20-20) and the RF processing unit (20-10) transmit and receive signals as described above. Accordingly, the baseband processing unit (20-20) and the RF processing unit (20-10) may be referred to as a transmitter, a receiver, a transceiver, or a communication unit. Furthermore, at least one of the baseband processing unit (20-20) and the RF processing unit (20-10) may include a plurality of communication modules to support a plurality of different wireless access technologies. In addition, at least one of the baseband processing unit (20-20) and the RF processing unit (20-10) may include different communication modules to process signals of different frequency bands. For example, the different wireless access technologies may include a wireless LAN (e.g., IEEE 802.11), a cellular network (e.g., LTE), etc. Additionally, the different frequency bands may include a super high frequency (SHF) (e.g., 2.NRHz, NRhz) band and a millimeter wave (mm wave) (e.g., 60GHz) band.

[0256] The storage unit (20-30) stores data such as basic programs, application programs, and setting information for the operation of the terminal. In particular, the storage unit (20-30) can store information related to a node performing wireless communication using wireless access technology. In addition, the storage unit (20-30) provides the stored data at the request of the control unit (20-40).

[0257] The control unit (20-40) controls the overall operations of the terminal. For example, the control unit (20-40) transmits and receives signals through the baseband processing unit (20-20) and the RF processing unit (20-10). In addition, the control unit (20-40) records and reads data in the storage unit (20-30). For this purpose, the control unit (20-40) may include at least one processor. For example, the control unit (20-40) may include a communication processor (CP) that performs control for communication and an application processor (AP) that controls upper layers such as application programs.

[0258] FIG. 21 is a block diagram showing the structure of a base station according to one embodiment of the present disclosure.

[0259] Here, a base station according to an embodiment of the present disclosure may refer to a base station, a first node, a second node, a master node, a secondary node, or an NTN cell described in the examples of the present disclosure. For example, a first node may refer to a node that first established a connection (e.g., an RRC connection) with a terminal, and a second node may refer to a node that last established a connection with a terminal or a node to which a connection was last added for the terminal.

[0260] Referring to FIG. 21, the base station may include an RF processing unit (21-10), a baseband processing unit (21-20), a backhaul communication unit (21-30), a storage unit (21-40), and a control unit (21-50).

[0261] The RF processing unit (21-10) performs functions for transmitting and receiving signals through a wireless channel, such as signal band conversion and amplification. That is, the RF processing unit (21-10) up-converts the baseband signal provided from the baseband processing unit (21-20) into an RF band signal and transmits it through an antenna, and down-converts the RF band signal received through the antenna into a baseband signal. For example, the RF processing unit (21-10) may include a transmission filter, a reception filter, an amplifier, a mixer, an oscillator, a DAC, an ADC, etc. In this drawing, only one antenna is illustrated, but multiple antennas may be provided. In addition, the RF processing unit (21-10) may include multiple RF chains. Furthermore, the RF processing unit (21-10) may perform beamforming. For the above beamforming, the RF processing unit (21-10) can adjust the phase and size of each signal transmitted and received through multiple antennas or antenna elements. The RF processing unit (21-10) can perform a downlink MIMO operation by transmitting one or more layers.

[0262] The baseband processing unit (21-20) above performs a conversion function between a baseband signal and a bit stream according to the physical layer specifications of the wireless access technology. For example, when transmitting data, the baseband processing unit (21-20) generates complex symbols by encoding and modulating a transmission bit stream. In addition, when receiving data, the baseband processing unit (21-20) restores the reception bit stream by demodulating and decoding the baseband signal provided from the RF processing unit (21-10). For example, in the case of OFDM, when transmitting data, the baseband processing unit (21-20) generates complex symbols by encoding and modulating a transmission bit stream, maps the complex symbols to subcarriers, and then configures OFDM symbols through IFFT operation and CP insertion. In addition, when receiving data, the baseband processing unit (21-20) divides the baseband signal provided from the RF processing unit (21-10) into OFDM symbol units, restores the signals mapped to subcarriers through FFT operation, and then restores the received bit string through demodulation and decoding. The baseband processing unit (21-20) and the RF processing unit (21-10) transmit and receive signals as described above. Accordingly, the baseband processing unit (21-20) and the RF processing unit (21-10) may be referred to as a transmitter, a receiver, a transceiver, a communication unit, or a wireless communication unit.

[0263] The above backhaul communication unit (21-30) provides an interface for performing communication with other nodes within the network. That is, the backhaul communication unit (21-30) converts a bit string transmitted from the main base station to other nodes, such as auxiliary base stations and core networks, into a physical signal, and converts a physical signal received from the other nodes into a bit string.

[0264] The storage unit (21-40) stores data such as basic programs, application programs, and setting information for the operation of the base station. In particular, the storage unit (21-40) can store information on bearers assigned to connected terminals, measurement results reported from connected terminals, and the like. In addition, the storage unit (21-40) can store information that serves as a judgment criterion for whether to provide or terminate multiple connections to a terminal. In addition, the storage unit (21-40) provides the stored data at the request of the control unit (21-50).

[0265] The control unit (21-50) controls the overall operations of the base station. For example, the control unit (21-50) transmits and receives signals through the baseband processing unit (21-20) and the RF processing unit (21-10) or through the backhaul communication unit (21-30). In addition, the control unit (21-50) records and reads data in the storage unit (21-40). For this purpose, the control unit (21-50) may include at least one processor.

[0266] In the specific embodiments of the present invention described above, components included in the invention are expressed in the singular or plural form depending on the specific embodiment presented. However, the singular or plural expressions are selected to suit the presented situation for convenience of explanation, and the present invention is not limited to singular or plural components. Even components expressed in the plural form may be composed of singular elements, or even components expressed in the singular form may be composed of plural elements.

[0267] While the detailed description of the present invention has described specific embodiments, it is clear that various modifications are possible without departing from the scope of the present invention. Therefore, the scope of the present invention should not be limited to the described embodiments, but should be defined not only by the scope of the following claims but also by equivalents thereof.

Claims

1. In a terminal method in a communication system, A step of receiving, from a base station, a measurement configuration message including configuration information of a measurement report for at least one non-terrestrial network (NTN) cell, wherein the configuration information includes information on an event of the measurement report; A step of performing measurement for at least one NTN cell based on the measurement setup message; Based on the above measurement, a step of identifying an NTN cell among the at least one NTN cell that satisfies the trigger condition of the event; and Comprising a step of transmitting a measurement report message including a measurement result for the identified NTN cell to the base station, A method of a terminal, characterized in that the information about the above event includes threshold information related to a time during which the at least one NTN cell can serve the terminal.

2. In paragraph 1, The above threshold information includes a threshold for the service time of the NTN cell, The time at which the terminal can be served is determined based on the time interval between a first point in time at which the elevation angle of the NTN cell for the terminal starts to increase from a minimum value and a second point in time at which the elevation angle starts to decrease from the minimum value. A method of a terminal, characterized in that if the time interval is greater than or equal to the threshold value, the trigger condition is determined to be satisfied.

3. In paragraph 1, The above threshold information includes a threshold value for the degree of elevation change of the NTN cell, and a minimum elevation angle related to the degree of elevation change, wherein the minimum elevation angle includes a first minimum elevation angle and a second minimum elevation angle greater than the first minimum elevation angle. The time that the terminal can be served is determined based on a comparison between the elevation angle and the minimum elevation angle when the elevation angle of the NTN cell changes to increase. If the degree of elevation change of the NTN cell for a given period of time is greater than or equal to the threshold value, the trigger condition is determined to be satisfied based on the elevation angle of the NTN cell being greater than the first minimum elevation angle, A method of a terminal characterized in that the trigger condition is determined to be satisfied based on the elevation angle of the NTN cell being greater than a second minimum elevation angle when the degree of elevation angle change of the NTN cell during the predetermined period of time is less than the threshold value.

4. In paragraph 1, The above threshold information includes a threshold value of the distance traveled by the NTN cell within a preset serving area or a threshold value of the angle at which the NTN cell enters the preset serving area toward the terminal. The above-described preset serving area is determined based on the altitude of the NTN cell and the location of the terminal. If the above threshold information includes a threshold value of the distance traveled by the NTN cell within the preset serving area, the time that can serve the terminal is confirmed based on the straight-line distance between the points where the preset serving area and the movement line of the NTN cell intersect with respect to a predetermined plane, If the above threshold information includes a threshold value of an angle at which the NTN cell enters the preset serving area toward the terminal, the time at which the terminal can be served is determined based on the angle between a tangent to a point at which the NTN cell enters the preset serving area on the predetermined plane and a direction in which the NTN cell moves from the point, A method of a terminal, characterized in that if the straight-line distance or the angle is greater than the threshold value, it is determined that the trigger condition is satisfied.

5. In a method of a base station in a communication system, A step of transmitting a measurement configuration message including configuration information of a measurement report for at least one non-terrestrial network (NTN) cell to a terminal; and A step of receiving, from the terminal, a measurement report message including a measurement result for an NTN cell among the at least one NTN cell based on the measurement setup message, The above setting information includes information about the event of the above measurement report, A method of a base station, characterized in that the information about the above event includes threshold information related to a time during which the at least one NTN cell can serve the terminal.

6. In paragraph 5, The above threshold information includes a threshold for the service time of the NTN cell, A method of a base station, characterized in that the measurement report message is received from the terminal based on a time interval between a first time point at which the elevation angle of the NTN cell for the terminal starts to increase from a minimum value and a second time point at which the elevation angle starts to decrease from the minimum value being greater than or equal to the threshold value.

7. In paragraph 5, The above threshold information includes a threshold value for the degree of elevation change of the NTN cell, and a minimum elevation angle related to the degree of elevation change, wherein the minimum elevation angle includes a first minimum elevation angle and a second minimum elevation angle greater than the first minimum elevation angle. A method of a base station, characterized in that the measurement report message is received from the terminal based on the degree of elevation angle increase of the NTN cell for a predetermined period of time being greater than or equal to the threshold value and the elevation angle of the NTN cell being greater than a first minimum elevation angle, or based on the degree of elevation angle increase of the NTN cell for the predetermined period of time being less than the threshold value and the elevation angle of the NTN cell being greater than a second minimum elevation angle.

8. In paragraph 5, The above threshold information includes a threshold value of the distance traveled by the NTN cell within a preset serving area or a threshold value of the angle at which the NTN cell enters the preset serving area toward the terminal. The above-described preset serving area is determined based on the altitude of the NTN cell and the location of the terminal. The above measurement report message is a method of a base station, characterized in that the above measurement report message is received from the terminal if the straight-line distance between points where the preset serving area and the moving line of the NTN cell intersect on a preset plane is greater than the threshold value, or if the angle between the tangent line to the point where the NTN cell enters the preset serving area on the preset plane and the direction in which the NTN cell moves from the point is greater than the threshold value.

9. In a terminal in a communication system, Transmitter and receiver; and A control unit for controlling the transceiver to receive, from a base station, a measurement configuration message including configuration information of a measurement report for at least one non-terrestrial network (NTN) cell, wherein the configuration information includes information about an event of the measurement report, perform measurement on the at least one NTN cell based on the measurement configuration message, identify an NTN cell satisfying a trigger condition of the event among the at least one NTN cell based on the measurement, and control the transceiver to transmit, to the base station, a measurement report message including a measurement result for the identified NTN cell, A terminal, characterized in that the information about the above event includes threshold information related to a time during which the at least one NTN cell can serve the terminal.

10. In paragraph 9, The above threshold information includes a threshold for the service time of the NTN cell, The terminal is characterized in that the control unit determines a time for serving the terminal based on a time interval between a first time point at which the elevation angle of the NTN cell for the terminal starts to increase from a minimum value and a second time point at which the elevation angle starts to decrease from the minimum value, and determines that the trigger condition is satisfied if the time interval is greater than or equal to the threshold value.

11. In paragraph 9, The above threshold information includes a threshold value for the degree of elevation change of the NTN cell, and a minimum elevation angle related to the degree of elevation change, wherein the minimum elevation angle includes a first minimum elevation angle and a second minimum elevation angle greater than the first minimum elevation angle. The control unit determines a time for serving the terminal based on a comparison between the elevation angle and the minimum elevation angle when the elevation angle of the NTN cell changes to increase, and determines that the trigger condition is satisfied based on the elevation angle of the NTN cell being greater than a first minimum elevation angle when the degree of elevation angle change of the NTN cell for a predetermined time is greater than or equal to the threshold value, and determines that the trigger condition is satisfied based on the elevation angle of the NTN cell being greater than a second minimum elevation angle when the degree of elevation angle change of the NTN cell for the predetermined time is less than the threshold value. The terminal is characterized in that.

12. In paragraph 9, The above threshold information includes a threshold value of the distance traveled by the NTN cell within a preset serving area or a threshold value of the angle at which the NTN cell enters the preset serving area toward the terminal. The above-described preset serving area is determined based on the altitude of the NTN cell and the location of the terminal. The control unit, if the threshold information includes a threshold value of a distance moved by the NTN cell within the preset serving area, determines a time that can serve the terminal based on a straight-line distance between points where the preset serving area and the moving line of the NTN cell meet with respect to a predetermined plane, and if the threshold information includes a threshold value of an angle at which the NTN cell enters the preset serving area toward the terminal, determines a time that can serve the terminal based on an angle between a tangent to a point at which the NTN cell enters the preset serving area on the predetermined plane and a direction in which the NTN cell moves from the point, and if the straight-line distance or the angle is greater than the threshold value, determines that the trigger condition is satisfied. The terminal according to claim 1, wherein:

13. In a base station in a communication system, Transmitter and receiver; and A terminal comprises a control unit for controlling the transceiver to transmit a measurement configuration message including configuration information of a measurement report for at least one non-terrestrial network (NTN) cell, and for controlling the transceiver to receive, from the terminal, a measurement report message including a measurement result for an NTN cell among the at least one NTN cell based on the measurement configuration message. The above setting information includes information about the event of the above measurement report, A base station, characterized in that the information about the above event includes threshold information related to a time during which the at least one NTN cell can serve the terminal.

14. In paragraph 13, The above threshold information includes a threshold for the service time of the NTN cell, A base station, characterized in that the above measurement report message is received from the terminal based on a time interval between a first time point at which the elevation angle of the NTN cell for the terminal starts to increase from a minimum value and a second time point at which the elevation angle starts to decrease from the minimum value being greater than or equal to the threshold value.

15. In paragraph 13, The above threshold information includes a threshold value for the degree of elevation change of the NTN cell, and a minimum elevation angle related to the degree of elevation change, wherein the minimum elevation angle includes a first minimum elevation angle and a second minimum elevation angle greater than the first minimum elevation angle. A base station characterized in that the measurement report message is received from the terminal based on the degree of elevation angle increase of the NTN cell for a predetermined period of time being greater than or equal to the threshold value and the elevation angle of the NTN cell being greater than a first minimum elevation angle, or based on the degree of elevation angle increase of the NTN cell for the predetermined period of time being less than the threshold value and the elevation angle of the NTN cell being greater than a second minimum elevation angle.

Images