Method and apparatus for configuring synchronization signal measurement timing in non-terrestrial network

Abstract

The present disclosure relates to a technique for configuring synchronization signal measurement timing in a non-terrestrial network. According to the present disclosure, a method of a terminal may be provided, the method comprising the steps of: receiving, from a non-terrestrial base station, synchronization signal measurement timing configuration (SMTC) configurations including information on reference locations; determining at least one SMTC configuration on the basis of proximities of the terminal to the reference locations of the SMTC configurations; and receiving at least one synchronization signal block (SSB) on the basis of the at least one SMTC configuration.

Description

Method and device for setting synchronization signal measurement timing in non-terrestrial networks

[0001] The present disclosure relates to a synchronization signal measurement timing setting technique in a non-terrestrial network, and more specifically, to a synchronization signal measurement timing setting technique in a non-terrestrial network that enables a terminal to receive a synchronization signal from a satellite providing a service by applying beam hopping technology.

[0002] To handle the rapidly increasing volume of wireless data, communication networks (e.g., new radio (NR) communication networks) that use frequency bands higher than the frequency bands of LTE (long term evolution) (or LTE-A) (e.g., frequency bands below 6 GHz) (e.g., frequency bands below 6 GHz) are being considered. NR communication networks can support frequency bands above 6 GHz as well as frequency bands below 6 GHz, and can support a wider variety of communication services and scenarios compared to LTE communication networks. For example, usage scenarios for NR communication networks may include eMBB (enhanced Mobile BroadBand), URLLC (Ultra Reliable Low Latency Communication), mMTC (massive Machine Type Communication), etc.

[0003] Such a communication network can be a terrestrial network as it provides communication services to terminals located on the ground. Recently, there has been an increasing demand for communication services not only on the ground but also for unmanned aerial vehicles and satellites located in non-terrestrial areas; to address this, technologies for non-terrestrial networks (NTNs) are being discussed at 3GPP. In non-terrestrial networks, satellites can utilize multi-beam hopping technology when providing services across multiple regions. Beam hopping technology is a technique in which a single satellite provides communication services by sequentially allocating beams to various geographical areas over time. In beam hopping technology, the satellite can transmit a synchronization signal block (SSB) to a specific region at a given time. The terminal can set an appropriate synchronization signal measurement timing configuration (SMTC) window to receive the SSB. However, due to the characteristics of beam hopping technology, there may be limitations in the terminal setting the SMTC window to a fixed value. An excessively long SMTC window can lead to wasted power and resources of the terminal. Conversely, a short SMTC window can cause SSB reception failure.

[0004] The objective of the present disclosure to solve the above-mentioned problems is to provide a method and apparatus for setting the timing of a synchronization signal measurement in a non-terrestrial network, which enables a terminal to receive a synchronization signal from a satellite providing services by applying beam hopping technology.

[0005] A method for setting synchronization signal measurement timing in a non-terrestrial network according to a first embodiment of the present disclosure for achieving the above objective may include, as a method of a terminal, the step of receiving synchronization signal measurement timing configuration (SMTC) configurations including information about reference locations from a non-terrestrial base station; the step of determining at least one SMTC configuration based on the proximity of the terminal to the reference locations of the SMTC configurations; and the step of receiving at least one synchronization signal block (SSB) based on the at least one SMTC configuration.

[0006] Here, each of the above SMTC settings may further include at least one of information regarding the SSB measurement period, information regarding the start time of the SMTC window, information regarding the length of the SMTC window, or information regarding the cell identifier.

[0007] Here, the step of determining at least one SMTC setting based on the proximity of the terminal to the reference locations of the SMTC settings may include: determining information about the location of the terminal; determining the distance between the location and each of the reference locations; and determining the at least one SMTC setting among the SMTC settings based on the distance.

[0008] Here, the step of determining information about the location of the terminal may include the step of determining information about the location of the terminal using at least one of a GNSS (global navigation satellite system), cell-based estimation, or a position measurement sensor.

[0009] Here, the information regarding the location may be at least one of information regarding latitude and longitude coordinates, cell ID (identifier)-based relative location information, or information regarding round-trip propagation delay with a non-ground base station.

[0010] Here, the step of receiving at least one SSB based on at least one SMTC setting may further include: determining whether the target cell associated with the at least one SMTC setting is a cell set by the non-ground base station; and adjusting the start time of the SMTC window of the at least one SMTC setting based on the fact that the target cell is not the cell set by the non-ground base station.

[0011] Here, the step of receiving at least one synchronization signal block (SSB) based on the at least one SMTC setting may further include: receiving a notification from the non-ground base station that the target cell associated with the at least one SMTC setting is a cell set by the non-ground base station different from the non-ground base station; and adjusting the start time of the SMTC window of the at least one SMTC setting.

[0012] Meanwhile, a method for setting synchronization signal measurement timing in a non-terrestrial network according to a second embodiment of the present disclosure for achieving the above objective comprises, as a method of a non-terrestrial base station, a step of generating candidate SMTC settings including information on reference locations for a serving cell of a terminal and adjacent cells; a step of transmitting information on reference locations for the serving cell and adjacent cells to a terminal; a step of requesting a reference location from the terminal; a step of receiving information on at least one reference location among the reference locations from the terminal; and a step of determining at least one SMTC setting from the candidate SMTC settings based on information on the at least one reference location, wherein the at least one reference location is determined based on the proximity of the terminal and each of the reference locations, and the proximity may be the distance between the location of the terminal and each of the reference locations.

[0013] Here, the at least one SMTC setting may further include at least one of information regarding the SSB measurement period, information regarding the start time of the SMTC window, information regarding the length of the SMTC window, or information regarding the cell identifier.

[0014] Herein, the method may further include the step of transmitting at least one SMTC setting to the terminal; the step of transmitting at least one SSB based on the at least one SMTC setting; and the step of receiving a measurement result for the at least one SSB from the terminal.

[0015] Herein, the method may further include a step of determining whether each of the adjacent cells is a cell set by the non-ground base station; and a step of adjusting the start time of the SMTC window included in the candidate SMTC setting of the first adjacent cell, which is a cell set by the non-ground base station among the adjacent cells.

[0016] Meanwhile, a synchronization signal measurement timing setting device in a non-ground network according to a third embodiment of the present disclosure for achieving the above objective comprises, as a terminal, at least one processor, and the at least one processor may cause the terminal to receive synchronization signal measurement timing configuration (SMTC) settings including information about reference locations from a non-ground base station; determine at least one SMTC setting based on the terminal's proximity to the reference locations of the SMTC settings; and cause at least one synchronization signal block (SSB) to be received based on the at least one SMTC setting.

[0017] Here, each of the above SMTC settings may further include at least one of information regarding the SSB measurement period, information regarding the start time of the SMTC window, information regarding the length of the SMTC window, or information regarding the cell identifier.

[0018] Here, in order to determine at least one SMTC setting based on the proximity of the terminal to the reference locations of the SMTC settings, the at least one processor may cause the terminal to determine information about the location of the terminal; determine the distance between the location and each of the reference locations; and determine the at least one SMTC setting in the SMTC settings based on the distance.

[0019] Here, in order to receive at least one SSB based on at least one SMTC setting, the at least one processor may further cause the terminal to determine whether the target cell associated with the at least one SMTC setting is a cell set by the non-ground base station; and to adjust the start time of the SMTC window of the at least one SMTC setting based on whether the target cell is not the cell set by the non-ground base station.

[0020] Here, in order to receive at least one SSB based on the at least one SMTC setting, the at least one processor may further cause the terminal to receive a notification from the non-ground base station that the target cell associated with the at least one SMTC setting is a cell set by the non-ground base station different from the non-ground base station; and may further cause the terminal to adjust the start time of the SMTC window of the at least one SMTC setting.

[0021] According to the present disclosure, a terminal can receive SMTC settings from a network and select SMTC settings based on the terminal's location. Accordingly, the terminal can receive SSBs with high accuracy at the location and increase the success rate of initial synchronization and cell search. In addition, the terminal can reduce unnecessary measurement attempts and reception waiting times and reduce power consumption.

[0022] FIG. 1 is a conceptual diagram illustrating embodiments of a non-ground network.

[0023] FIG. 2 is a conceptual diagram illustrating embodiments of a non-ground network.

[0024] FIG. 3 is a block diagram illustrating embodiments of entities constituting a non-ground network.

[0025] FIGS. 4a to 4d are conceptual diagrams illustrating embodiments of synchronous signal measurement timing settings in a clustered cell investigation scenario.

[0026] FIGS. 5a and 5b are conceptual diagrams illustrating examples of synchronous signal measurement timing settings in a distributed cell investigation scenario.

[0027] FIG. 6 is a flowchart illustrating an example of a method for setting the timing of a synchronous signal measurement in a non-terrestrial network.

[0028] FIG. 7 is a flowchart illustrating an example of a method for setting the timing of a synchronous signal measurement in a non-terrestrial network.

[0029] Figure 8 is a conceptual diagram illustrating a serving cell and an adjacent cell in a multi-satellite environment.

[0030] Figures 9a and 9b are conceptual diagrams for explaining propagation delay in a multi-satellite environment.

[0031] The present disclosure is capable of various modifications and may have various embodiments, and specific embodiments are illustrated in the drawings and described in detail. However, this is not intended to limit the present disclosure to specific embodiments, and it should be understood that it includes all modifications, equivalents, and substitutions that fall within the spirit and scope of the present disclosure.

[0032] Terms such as "first," "second," etc., may be used to describe various components, but said components should not be limited by said terms. Such terms are used solely for the purpose of distinguishing one component from another. For example, without departing from the scope of the present disclosure, the first component may be named the second component, and similarly, the second component may be named the first component. The term "and / or" includes a combination of a plurality of related described items or any of a plurality of related described items.

[0033] In embodiments of the present disclosure, "at least one of A and B" may mean "at least one of A or B" or "at least one of one or more combinations of A and B". Additionally, in embodiments of the present disclosure, "at least one of A and B" may mean "at least one of A or B" or "at least one of one or more combinations of A and B".

[0034] When it is stated that one component is "connected" or "connected" to another component, it should be understood that while it may be directly connected or connected to that other component, there may also be other components in between. On the other hand, when it is stated that one component is "directly connected" or "directly connected" to another component, it should be understood that there are no other components in between.

[0035] In the present disclosure, a phrase containing "~ case (e.g., when ~)" may be expressed as a phrase containing "~ based on (e.g., based on ~)" or a phrase containing "~ in response to (e.g., in response to ~)". In other words, a phrase containing "~ case" may be interpreted as identical or similar to a phrase containing "~ based on" or a phrase containing "~ in response to".

[0036] The terms used in this disclosure are used merely to describe specific embodiments and are not intended to limit this disclosure. The singular expression includes the plural expression unless the context clearly indicates otherwise. In this disclosure, terms such as “comprising” or “having” are intended to specify the existence of the features, numbers, steps, actions, components, parts, or combinations thereof described in the specification, and should be understood as not precluding the existence or addition of one or more other features, numbers, steps, actions, components, parts, or combinations thereof.

[0037] Unless otherwise defined, all terms used herein, including technical or scientific terms, have the same meaning as generally understood by those skilled in the art to which this disclosure pertains. Terms such as those defined in commonly used dictionaries should be interpreted as having a meaning consistent with their meaning in the context of the relevant technology, and should not be interpreted in an ideal or overly formal sense unless explicitly defined in this disclosure.

[0038] Hereinafter, preferred embodiments of the present disclosure will be described in more detail with reference to the attached drawings. In order to facilitate an overall understanding of the present disclosure, the same reference numerals are used for identical components in the drawings, and redundant descriptions of identical components are omitted.

[0039] A communication network to which embodiments according to the present disclosure are applied will be described. The communication system may be a non-terrestrial network (NTN), a 4G (4th Generation) communication network (e.g., an LTE (long-term evolution) communication network), a 5G (5th Generation) communication network (e.g., an NR (new radio) communication network), a 6G (6th Generation) communication network, etc. The 4G communication network, the 5G communication network, and the 6G communication network may be classified as terrestrial networks.

[0040] Non-terrestrial networks may operate based on LTE technology and / or NR technology. Non-terrestrial networks may support communication in frequency bands above 6 GHz as well as in frequency bands below 6 GHz. 4G communication networks may support communication in frequency bands below 6 GHz. 5G communication networks may support communication in frequency bands above 6 GHz as well as in frequency bands below 6 GHz. The communication networks to which the embodiments according to the present disclosure are applied are not limited to those described below, and the embodiments according to the present disclosure may be applied to various communication networks. Here, the term "communication network" may be used interchangeably with "communication system."

[0041] FIG. 1 is a conceptual diagram illustrating embodiments of a non-ground network.

[0042] Referring to FIG. 1, the non-ground network may include a satellite (110), a communication node (120), a gateway (130), a data network (140), etc. The non-ground network illustrated in FIG. 1 may be a non-ground network based on a transparent payload. The satellite (110) may be a LEO (low earth orbit, altitude 300 to 1,500 km) satellite, a MEO (medium earth orbit, altitude 7,000 to 25,000 km) satellite, a GEO (geostationary earth orbit, altitude about 35,786 km) satellite, a HEO (high elliptical orbit) satellite, or an UAS (unmanned aircraft system) platform. The UAS platform may include a HAPS (high altitude platform station).

[0043] The communication node (120) may include a communication node located on the ground (e.g., UE (user equipment), terminal) and a communication node located off the ground (e.g., airplane, drone). A service link may be established between the satellite (110) and the communication node (120), and the service link may be a radio link. The satellite (110) may provide communication services to the communication node (120) using one or more beams. The shape of the receiving range (footprint) of the satellite (110) beam may be elliptical.

[0044] A communication node (120) can communicate with a satellite (110) (e.g., downlink communication, uplink communication) using LTE technology and / or NR technology. Communication between the satellite (110) and the communication node (120) can be performed using an NR-Uu interface. If dual connectivity (DC) is supported, the communication node (120) can be connected to the satellite (110) as well as other base stations (e.g., base stations supporting LTE and / or NR functions), and can perform DC operations based on technology defined in LTE and / or NR specifications.

[0045] The gateway (130) may be located on the ground, and a feeder link may be established between the satellite (110) and the gateway (130). The feeder link may be a wireless link. The gateway (130) may be referred to as a "non-terrestrial network (NTN) gateway." Communication between the satellite (110) and the gateway (130) may be performed based on an NR-Uu interface or a satellite radio interface (SRI). The gateway (130) may be connected to a data network (140). A "core network" may exist between the gateway (130) and the data network (140). In this case, the gateway (130) may be connected to the core network, and the core network may be connected to the data network (140). The core network may support NR technology. For example, the core network may include an access and mobility management function (AMF), a user plane function (UPF), a session management function (SMF), etc. Communication between the gateway (130) and the core network can be performed based on the NG-C / U interface.

[0046] Alternatively, a base station and a core network may exist between the gateway (130) and the data network (140). In this case, the gateway (130) may be connected to the base station, the base station may be connected to the core network, and the core network may be connected to the data network (140). The base station and the core network may support NR technology. Communication between the gateway (130) and the base station may be performed based on an NR-Uu interface, and communication between the base station and the core network (e.g., AMF, UPF, SMF) may be performed based on an NG-C / U interface.

[0047] FIG. 2 is a conceptual diagram illustrating embodiments of a non-ground network.

[0048] Referring to FIG. 2, the non-ground network may include satellite #1 (211), satellite #2 (212), a communication node (220), a gateway (230), a data network (240), etc. The non-ground network illustrated in FIG. 2 may be a regenerative payload-based non-ground network. For example, each of satellites #1-2 (211, 212) may perform a regenerative operation (e.g., demodulation, decoding, re-coding, re-modulation, and / or filtering) on ​​a payload received from other entities constituting the non-ground network (e.g., communication node (220), gateway (230)), and may transmit the regenerative payload.

[0049] Each of satellites #1-2 (211, 212) may be a LEO satellite, MEO satellite, GEO satellite, HEO satellite, or UAS platform. A UAS platform may include a HAPS. Satellite #1 (211) may be connected to satellite #2 (212), and an inter-satellite link (ISL) may be established between satellite #1 (211) and satellite #2 (212). The ISL may operate in a radio frequency (RF) band or an optical band. The ISL may be established optionally. Communication nodes (220) may include communication nodes located on the ground (e.g., UE, terminal) and communication nodes located off the ground (e.g., airplane, drone). A service link (e.g., a wireless link) may be established between satellite #1 (211) and communication nodes (220). Satellite #1 (211) can provide communication services to a communication node (220) using one or more beams.

[0050] The communication node (220) can communicate with satellite #1 (211) (e.g., downlink communication, uplink communication) using LTE technology and / or NR technology. Communication between satellite #1 (211) and the communication node (220) can be performed using an NR-Uu interface. If DC is supported, the communication node (220) can be connected to satellite #1 (211) as well as other base stations (e.g., base stations supporting LTE and / or NR functions) and can perform DC operations based on technology defined in the LTE and / or NR specifications.

[0051] The gateway (230) may be located on the ground, and a feeder link may be established between satellite #1 (211) and the gateway (230), and a feeder link may be established between satellite #2 (212) and the gateway (230). The feeder link may be a wireless link. If an ISL is not established between satellite #1 (211) and satellite #2 (212), a feeder link between satellite #1 (211) and the gateway (230) may be established mandatorily.

[0052] Communication between each of satellites #1-2 (211, 212) and the gateway (230) can be performed based on an NR-Uu interface or SRI. The gateway (230) can be connected to a data network (240). A "core network" may exist between the gateway (230) and the data network (240). In this case, the gateway (230) can be connected to the core network, and the core network can be connected to the data network (240). The core network may support NR technology. For example, the core network may include AMF, UPF, SMF, etc. Communication between the gateway (230) and the core network can be performed based on an NG-C / U interface.

[0053] Alternatively, a base station and a core network may exist between the gateway (230) and the data network (240). In this case, the gateway (230) may be connected to the base station, the base station may be connected to the core network, and the core network may be connected to the data network (240). The base station and the core network may support NR technology. Communication between the gateway (230) and the base station may be performed based on an NR-Uu interface, and communication between the base station and the core network (e.g., AMF, UPF, SMF) may be performed based on an NG-C / U interface.

[0054] Meanwhile, entities constituting the non-terrestrial network shown in FIGS. 1 and 2 (e.g., satellite, communication node, gateway, etc.) can be configured as follows.

[0055] FIG. 3 is a block diagram illustrating embodiments of entities constituting a non-ground network.

[0056] Referring to FIG. 3, the entity (300) may include at least one processor (310), a memory (320), and a transceiver (330) that communicates by being connected to a network. Additionally, the entity (300) may further include an input interface device (340), an output interface device (350), a storage device (360), etc. Each component included in the entity (300) may communicate with one another by being connected by a bus (370).

[0057] However, each component included in the entity (300) may be connected via individual interfaces or individual buses centered around the processor (310), rather than via a common bus (370). For example, the processor (310) may be connected via a dedicated interface to at least one of a memory (320), a transmission / reception device (330), an input interface device (340), an output interface device (350), and a storage device (360).

[0058] The processor (310) can execute a program command stored in at least one of the memory (320) and the storage device (360). The processor (310) may mean a central processing unit (CPU), a graphics processing unit (GPU), or a dedicated processor on which the methods according to embodiments of the present disclosure are performed. Each of the memory (320) and the storage device (360) may be composed of at least one of a volatile storage medium and a non-volatile storage medium. For example, the memory (320) may be composed of at least one of read-only memory (ROM) and random access memory (RAM).

[0059] Meanwhile, in non-terrestrial networks, scenarios can be defined as shown in Table 1 below.

[0060] NTN shown in Fig. 1, NTNGEO shown in Fig. 2, Scenario A, BLEO (Adjustable Beam) Scenario C1, Scenario D1, LEO (Beam Moving with Satellite) Scenario C2, Scenario D2

[0061] In the non-ground network shown in FIG. 1, if the satellite (110) is a GEO satellite (e.g., a GEO satellite that supports transparent functions), this may be referred to as “Scenario A”. In the non-ground network shown in FIG. 2, if satellite #1-2 (211, 212) is a GEO satellite (e.g., a GEO that supports regenerative functions), this may be referred to as “Scenario B”.

[0062] In the non-ground network illustrated in FIG. 1, if the satellite (110) is an LEO satellite having steerable beams, this may be referred to as "Scenario C1". In the non-ground network illustrated in FIG. 1, if the satellite (110) is an LEO satellite having beams that move with the satellite, this may be referred to as "Scenario C2". In the non-ground network illustrated in FIG. 2, if satellite #1-2 (211, 212) is an LEO satellite having steerable beams, this may be referred to as "Scenario D1". In the non-ground network illustrated in FIG. 2, if satellite #1-2 (211, 212) is an LEO satellite having beams that move with the satellite, this may be referred to as "Scenario D2". The parameters for the scenarios defined in Table 1 may be defined as shown in Table 2 below.

[0063] Scenarios A and B Scenarios C and D Elevation 35,786 km 600 km 1,200 km Spectrum (Service Link) < 6 GHz (e.g., 2 GHz) > 6 GHz (e.g., DL 20 GHz, UL 30 GHz) Maximum Channel Bandwidth Capacity (Service Link) 30 MHz for band < 6 GHz 1 GHz for band > 6 GHz Maximum Distance between Satellite and Communication Node (e.g., UE) at Minimum Elevation Angle 40,581 km 1,932 km (600 km altitude) 3,131 km (1,200 km altitude) Maximum RTD (Round Trip Delay) (Propagation Delay Only) Scenario A: 541.46 ms (Service and Feeder Links) Scenario B: 270.73 ms (Service Link Only) Scenario C: (Transparent Payload: Service and Feeder Links) - 25.77 ms (600 km Altitude) - 41.77ms (1200km altitude) Scenario D: (Regenerate Payload: Service Link Only) - 12.89ms (600km altitude) - 20.89ms (1200km altitude) Maximum differential latency within a single cell 10.3ms 3.12ms (600km altitude) 3.18ms (1200km altitude) Service Link NR or 6G Feeder Link 3GPP or non-3GPP defined radio interface

[0064] In addition, in the scenarios defined in Table 1, the delay constraint can be defined as shown in Table 3 below.

[0065] Scenario A Scenario B Scenario C1-2 Scenario D1-2 Satellite Altitude 35,786 km 600 km Maximum RTD at radio interface between base station and UE 541.75 ms (Worst case) 270.57 ms 28.41 ms 12.88 ms Minimum RTD at radio interface between base station and UE 477.14 ms 238.57 ms 8 ms 4 ms

[0066] In the following, methods for setting the timing of receiving a synchronization signal in a communication system will be described. Even when a method performed by a first communication node among the communication nodes (e.g., transmission or reception of a signal) is described, the corresponding second communication node may perform a method corresponding to the method performed by the first communication node (e.g., reception or transmission of a signal). That is, when the operation of a terminal is described, the corresponding base station may perform an operation corresponding to the operation of the terminal. Conversely, when the operation of a base station is described, the corresponding terminal may perform an operation corresponding to the operation of the base station.

[0067] Satellites can utilize multi-beam hopping technology when providing services across multiple regions. By using multi-beam hopping technology, satellites can generate multiple beams to provide services to various areas on the ground. Furthermore, by using multi-beam hopping technology to hop beams to different regions over time, satellites can efficiently utilize frequency resources and optimize service coverage. Such multi-beam hopping technology may have the following characteristics.

[0068] - Beam Generation: A satellite can generate multiple directional beams using an antenna array. The satellite can then provide communication services by targeting specific areas on the ground with each beam.

[0069] - Time Division Multiple Access: Satellites can use the Time Division Multiple Access (TDMA) method to enable each beam to provide service to an area corresponding to a specific time slot.

[0070] - Beam Hopping: A satellite can move a beam to a different area according to a specific pattern or schedule.

[0071] - Service Optimization: Satellites can optimize specific patterns based on traffic demand, regional service requirements, etc.

[0072] - Communication with the terminal: The terminal can know the satellite's beam hopping schedule. Accordingly, the terminal can perform communication when the corresponding beam hops to its area.

[0073] Satellites can maximize the capacity of satellite communications, increase the utilization of the frequency spectrum, and effectively provide services to various regions by using multi-beam hopping technology. Therefore, 3GPP is discussing the application of beam hopping technology to non-terrestrial network (NTN) systems. A technology for dynamically scheduling beam hopping may be necessary to fully utilize the advantages of multi-beam hopping technology.

[0074] To apply beam hopping technology in a non-terrestrial network system, beam footprints may have at least one of three states, N1, N2, or N3, to enable the use of beam hopping technology.

[0075] (1) Beam reception range in N1 state

[0076] The operating status of the beam reception range in N1 state may be "transmit off". The beam reception range in N1 state may not provide any satellite signals. The beam reception range in N1 state cannot provide satellite services. The transmit off operation may mean a transmit stop operation.

[0077] (2) Beam reception range in N2 state

[0078] The operational status of the beam reception range in the N2 state may be "common message only". The beam reception range in the N2 state cannot provide active user traffic. The beam reception range in the N2 state can provide only essential information for cell discovery and initial access. Optionally, the operator may consider user arrivals (e.g., RACH (random access channel) access) in cells of the beam reception range in the N2 state. The operator may explain how user arrivals were reflected in the analytic evaluation.

[0079] (3) Beam reception range in N3 state

[0080] The operating status of a beam reception range in the N3 state may be "active traffic". Each beam reception range in the N3 state may have X active users, such as VoNR (voice over new radio). X can be a positive integer. A beam reception range in the N3 state may provide essential information for cell discovery and initial connection.

[0081] Non-terrestrial networks can appropriately support transitions between three states (e.g., N1, N2, and N3 states) to apply beam hopping technology without affecting service provision. The actual satellite beam can be activated in the N2 and N3 states. In the N2 and N3 states, the synchronization signal block (SSB) transmission period and synchronization signal measurement timing configuration (SMTC) window can be appropriately set according to the beam's dwell time and revisit time.

[0082] Non-terrestrial networks can apply discontinuous transmission (DTX) and discontinuous reception (DRX) methods of network energy saving (NES) technology to efficiently apply beam hopping technology. NES technology can use cell DTX and cell DRX mechanisms for energy saving. In the case of cell DTX, each serving cell can configure a periodic DTX pattern with active and non-active cycles by radio resource control (RRC). Depending on the DTX pattern set in the serving cell, the terminal may not monitor the physical downlink control channel (PDCCH) and semi-persistent scheduling (SPS) during the non-active cycle.

[0083] On the other hand, in the case of cell DRX, each serving cell can configure a periodic DRX pattern having an active period and an inactive period by the RRC. Depending on the DRX pattern set in the serving cell, the terminal may not perform transmissions on configured grant (CG) resources, scheduling request (SR) transmissions, periodic or semi-persistent channel state information (CSI) reporting, and sounding reference signal (SRS) transmissions during the inactive period.

[0084] Cell DTX and cell DRX mechanisms can be similarly applied to NTNs where beam hopping is applied. For example, in non-ground networks, the period during which the satellite beam is active can be considered as the active cycle, and the period during which it is deactivated can be considered as the inactive cycle, thereby configuring a beam hopping DTX pattern.

[0085] The DRX / DTX configuration of NES can be cell-based. In non-ground networks, a single satellite beam can form a single cell, or multiple satellite beams can form a single cell. Therefore, it may be difficult to apply cell DTX and cell DRX mechanisms in non-ground networks. Additionally, in the case of non-ground networks based on low-orbit satellites, frequent handovers between beams or between satellites may occur due to satellite movement. If a non-ground network applies beam hopping technology during handover situations caused by satellite mobility, it may negatively affect handover performance.

[0086] The next-generation satellite communication system, NR-NTN (new radio-non terrestrial network), can provide wide coverage by dividing it temporally through beam hopping technology. In this structure, the SSB transmission time may vary from beam to beam. A terminal may require precise control of the SMTC window to receive the SSB at an appropriate time. This disclosure, particularly based on the SMTC configuration mechanism defined in Release 18, can explain the limitations of SMTC configuration in various beam hopping scenarios and provide methods for improving SMTC configuration.

[0087] 3GPP may be actively discussing whether there are any limitations to existing SMTC configurations by considering both clustered-cell illumination and scattered-cell illumination methods in a beam-hopping environment. NTN systems applying beam-hopping can provide clustered-cell illumination scenarios and scattered-cell illumination scenarios depending on the beam-hopping pattern. Specifically, in a clustered-cell illumination scenario, multiple adjacent beams can be activated simultaneously. In a scattered-cell illumination scenario, non-adjacent beams can be activated simultaneously.

[0088] FIGS. 4a to 4d are conceptual diagrams illustrating embodiments of synchronous signal measurement timing settings in a clustered cell investigation scenario.

[0089] Referring to Fig. 4a, seven cells can form a cluster cell. Such a cluster cell can be called a 7-cluster cell. Referring to Fig. 4b, four cells can form a cluster cell. Such a cluster cell can be called a 4-cluster cell. Referring to Fig. 4c, three cells can form a cluster cell. Such a cluster cell can be called a 3-cluster cell. Referring to Fig. 4d, two cells can form a cluster cell. Such a cluster cell can be called a 2-cluster cell.

[0090] The existing SMTC mechanism may have up to four SMTC windows and may be insufficient in a cluster cell illumination scenario. For example, referring to FIGS. 4a and 4b, seven cells and four cells may each form a cluster cell. In this case, the satellite (410) can illuminate the cells forming a cluster cell using beams. In this situation, all beams illuminating the cells of a cluster cell can be activated simultaneously. The terminal (420) can receive SSBs transmitted through the beams illuminating the cells of a cluster cell using one SMTC window.

[0091] The activation times of each beam in the cluster cells may differ. Therefore, an SMTC window may be required for each of the cluster cells. When the terminal is at a specific location (e.g., the center of the circle in FIG. 4a and FIG. 4b), the network can configure up to three SMTC windows in the case of FIG. 4a. The network can configure up to four SMTC windows in the case of FIG. 4b. Existing SMTC mechanisms can support 7-cluster cells and 4-cluster cells.

[0092] In contrast, when the terminal is at a specific location (e.g., the center of the circle in FIG. 4c and FIG. 4d), the network may require up to 5 SMTC windows in the case of FIG. 4c. The network may require up to 6 SMTC windows in the case of FIG. 4d. Existing SMTC mechanisms can support up to 4 SMTC windows. Accordingly, existing SMTC mechanisms may have difficulty supporting the 3-cluster cell of FIG. 4c. Additionally, existing SMTC mechanisms may have difficulty supporting a 2-cluster group.

[0093] FIGS. 5a and 5b are conceptual diagrams illustrating examples of synchronous signal measurement timing settings in a distributed cell investigation scenario.

[0094] Referring to FIG. 5a, the cells may be randomly distributed. Such cells can be described as randomly distributed cells. The satellite (510) may transmit SSBs toward the terminal (520) at randomly different times for the randomly distributed cells. The number of SMTC windows in the randomly distributed cells may exceed four to prevent interference. The existing SMTC mechanism may have a maximum of four SMTC windows. The existing SMTC mechanism may have insufficient SMTC windows in the randomly distributed cells.

[0095] Referring to FIG. 5b, the cells may be randomly distributed and may form distributed groups (530-1, 530-2). Such cells may be referred to as group-based distributed cells. In group-based distributed cells, one beam per distributed group may be activated. In group-based distributed cells, the satellite (510) may transmit SSBs using beams simultaneously to adjacent distributed groups. The existing SMTC mechanism may have up to four SMTC windows. The terminal (520) may receive SSBs transmitted via beam hopping in group-based distributed cells using the SMTC windows supported by the existing SMTC mechanism.

[0096] In other group-based distributed cells, a single satellite can service up to 1,058 beam reception ranges with 16 active beams. In other group-based distributed cells, adjacent distributed groups can transmit SSBs at different times. The existing SMTC mechanism can have up to 4 SMTC windows. In such distributed cells, terminals may have difficulty receiving SSBs using the SMTC windows according to the existing SMTC mechanism.

[0097] In the case of distributed cells, adjacent cells can transmit SSBs independently at different times. Therefore, existing SMTC mechanisms with SMTC windows limited to a maximum of four may struggle to achieve sufficient effectiveness in various beam-hopping scenarios. In particular, complex distributed cell probing patterns may require up to six SMTC windows. In clustered cell probing scenarios, some configurations (e.g., cases where multiple small clusters exist) may require more than four SMTC windows. Accordingly, non-terrestrial networks can extend the maximum number of SMTC windows to six for terminals in RRC idle and RRC disabled states.

[0098] Non-terrestrial networks can apply beam hopping technology within a range that does not increase the maximum number of SMTCs or measurement gaps that must be considered simultaneously at the terminal according to the existing SMTC mechanism. In contrast, for beam hopping scenarios where the number of SMTC windows required exceeds the limit according to the existing SMTC mechanism as described above, non-terrestrial networks may consider the following solutions.

[0099] For example, a non-terrestrial network may apply a terminal location-based SMTC selection method performed at the terminal side. The maximum number of SMTC windows may be increased in the terminal location-based SMTC selection method. For example, the maximum number of SMTC windows may be increased up to 7 in the terminal location-based SMTC selection method. The network may configure SMTC windows corresponding to the maximum number. In the terminal location-based SMTC selection method, each SMTC window may be associated with a reference location (for example, the center of the cell where the terminal is expected to measure the SSB using that SMTC window).

[0100] FIG. 6 is a flowchart illustrating an example of a method for setting the timing of a synchronous signal measurement in a non-terrestrial network.

[0101] Referring to FIG. 6, the network can transmit information to the terminal regarding settings (which can be abbreviated as SMTC settings) for various SMTC windows connected to each reference location. The terminal can receive information from the network regarding various SMTC settings connected to each reference location (S610). The terminal can determine its current location (S620). For example, the terminal can determine its current location based on GNSS (global navigation satellite system). The terminal can determine its current location through cell-based estimation. The terminal can determine its current location using a location measurement sensor.

[0102] The terminal can identify reference locations from several received SMTC settings. The terminal can select at least one SMTC setting from several SMTC settings based on proximity to the reference locations (S630). For example, the terminal can select one SMTC setting corresponding to the reference location closest to the terminal from several SMTC settings based on proximity to the reference locations. In other words, the terminal can select one SMTC setting associated with the reference location corresponding to the shortest distance between the terminal's location and the reference locations. In this way, the terminal can select one SMTC setting to optimize power consumption. The terminal can receive SSB from the satellite based on the SMTC window according to the selected SMTC setting (S640).

[0103] As another example, the terminal can select N SMTC settings in order of reference locations closest to the terminal from several SMTC settings based on proximity to reference locations (S630). N can be a positive integer. N can be, for example, 6, 7, 8, etc. In other words, the terminal can select N SMTC settings in order of shortest distance from the terminal's location to the reference locations.

[0104] The terminal can select N SMTC settings from several SMTC settings based on the distances between the terminal's location and reference locations. The terminal can form a subset of SMTCs with the selected N SMTC settings. For example, the terminal can select SMTC settings in order of proximity between its current location and the reference location. The terminal can select SMTC settings up to the maximum number of SMTCs that can be monitored simultaneously. The terminal can select SMTC setting information up to the maximum number that can be monitored simultaneously based on the determined distances. The terminal can receive SSBs from the satellite based on SMTC windows according to the selected SMTC settings (S640).

[0105] Specifically, in a terminal location-based SMTC selection method performed at the terminal side, the network can transmit multiple SMTC configuration information to the terminal. The network can deliver the SMTC configuration information to the terminal through RRC (radio resource control) signaling, for example, an RRC reset message. The terminal can receive multiple SMTC configuration information from the network. For example, the terminal can receive SMTC configuration information from the network through RRC signaling, for example, an RRC reset message.

[0106] Each of the SMTC configuration information may be associated with a single reference location. For example, the reference location may be the center location of a cell or beam where the SSB is expected to be measured using the SMTC window determined by the corresponding SMTC configuration at the terminal. However, the reference location may not be limited thereto. Each of the SMTC configuration information may include at least one of an SMTC identifier, a reference location (e.g., latitude and longitude coordinates, cell identifier, etc.), a reference SSB, or a timing window (e.g., start time, start offset, length, period, etc.).

[0107] The terminal can determine its location through position measurement technologies such as GNSS or cell-based estimation, and can determine the distance between its location and each reference location of the SMTC setting information. The terminal can sort the SMTC setting information based on the determined distances. Based on the determined distances, the terminal can select the SMTC setting information with the shortest distance, considering power consumption optimization. Alternatively, the terminal can select up to the maximum number of SMTC setting information that can be monitored simultaneously based on the determined distances. The terminal can measure SSB at a time (e.g., SMTC window) corresponding to the selected SMTC setting information.

[0108] The terminal can obtain time and frequency synchronization using the primary synchronization signal (PSS) and secondary synchronization signal (SSS) of the SSB, and can obtain the physical cell identifier (PCI). The terminal can obtain the master information block (MIB) through the physical broadcast channel (PBCH) included in the SSB. Based on the MIB, the terminal can obtain the minimum parameters required to receive the system information block 1 (SIB1) and can receive the SIB1 through the physical downlink control channel (PDCCH) and physical downlink shared channel (PDSCH). The terminal can obtain the SIBs and determine whether to select a cell or camp. The terminal can decide to camp and, if a connection is required, can proceed with the initial connection procedure based on the random access channel (RACH).

[0109] As another example, the terminal can report the measurement results of the SSB to the network. The terminal can report the measurement results of the SSB to the network via a measurement report, for example, through a measurement report message. The network can receive the measurement results of the SSB from the terminal via a measurement report message. Alternatively, the terminal can report the measurement results of the SSBs to the network. For example, the terminal can report the measurement results of the SSBs to the network via a measurement report, for example, through a measurement report message. The network can receive the measurement results of the SSBs from the terminal via a measurement report message. For example, the terminal can measure cell quality such as SS-RSRP (synchronization signal reference signal received power), SS-RSRQ (synchronization signal reference signal received quality), or SS-SINR (synchronization signal signal-to-interference-plus-noise) from the SSBs or SSBs within the SMTC window. The terminal can determine whether a measurement event is triggered based on the measurement results or the measurement results.

[0110] When the terminal determines that a measurement event has been triggered, it may report the measurement result or the measurement results to the network. The network may receive the measurement result or the measurement results from the terminal. Based on the received measurement result or the measurement results, the network may perform mobility decisions such as handover, PSCell (primary secondary cell) change, or Scell ​​(secondary cell) activation. Accordingly, the terminal and the network may perform handover, PSCell change, or Scell ​​activation.

[0111] A non-terrestrial network may apply a terminal location-based SMTC configuration method performed on the network side. The maximum number of SMTC windows configured in the terminal location-based SMTC configuration method performed on the network side may not increase beyond the maximum number of existing SMTC mechanisms (for example, the maximum number of SMTC windows may be 4). The network may select a single SMTC configuration information considering power consumption optimization. Alternatively, the network may select up to the maximum number of SMTC configuration information that can be monitored simultaneously.

[0112] FIG. 7 is a flowchart illustrating an example of a method for setting the timing of a synchronous signal measurement in a non-terrestrial network.

[0113] Referring to FIG. 7, the network can generate information about candidate SMTC settings. Each of the candidate SMTC settings may be associated with a reference location. For example, the reference location may be the center location of a cell or beam where the terminal is expected to measure the SSB using the SMTC window according to the corresponding SMTC setting. The reference location may not be limited thereto. The network may provide information about the reference locations to the terminal (S710). The terminal may receive information about the reference locations from the network. Alternatively, the network may provide the terminal with information about candidate SMTC settings that include information about the reference locations. The terminal may receive information about candidate SMTC settings that include information about the reference locations from the network.

[0114] The network may request the terminal to report location information (S720). In other words, the network may request the terminal to report information related to its current location. This request for reporting location information may mean that the network requests the terminal to determine one reference location or a subset of reference locations based on the proximity of the terminal's current location (e.g., location obtained through GNSS or cell-based estimation) and the reference locations. Proximity may mean the distance between the terminal's current location and each of the reference locations. In this way, through the request for reporting location information, the network may request the terminal to determine one reference location or a subset of reference locations with the shortest distance based on the distances between the terminal's current location (e.g., location obtained through GNSS or cell-based estimation) and the reference locations.

[0115] The terminal may receive a request to report location information from the network (S720). In other words, the terminal may receive a request to report information related to its current location from the network. Receiving such a report request may mean that the terminal receives a request from the network to determine one reference location or a subset of reference locations based on the proximity of the terminal's current location (e.g., a location obtained through GNSS or cell-based estimation) and reference locations. In this way, through the reception of the report request, the terminal may receive a request from the network to determine one reference location or a subset of reference locations with the shortest distance based on the distances between the terminal's current location (e.g., a location obtained through GNSS or cell-based estimation) and reference locations.

[0116] The terminal can determine its location through position measurement techniques, such as GNSS or cell-based estimation, in response to a request from the network, and can determine the distance between each of the reference locations and its location. The terminal can sort the reference locations based on the determined distances. Based on the determined distances, the terminal can determine the reference location with the shortest distance, taking into account power consumption optimization. Alternatively, the terminal can determine up to the maximum number of reference locations that can be monitored simultaneously based on the determined distances, and can determine a subset of reference locations from the determined reference locations. The terminal can report the determined reference location (or reference location identifier) ​​to the network. The terminal can report a subset of reference locations (a subset of reference location identifiers) consisting of the selected reference locations to the network (S730). The network can receive information regarding the reference location (or reference location identifier) ​​from the terminal. The network can receive information regarding a subset of reference locations (or a subset of reference location identifiers) consisting of the reference locations from the terminal.

[0117] The network can determine one SMTC setting from candidate SMTC settings by considering power consumption optimization based on information regarding a reference location (or reference location identifier) ​​or a subset of reference locations (or a subset of reference location identifiers) received from the terminal. The network can determine SMTC settings that can be simultaneously monitored by the terminal from candidate SMTC settings based on information regarding a reference location (or reference location identifier) ​​or a subset of reference locations (or a subset of reference location identifiers) received from the terminal.

[0118] The network can transmit information regarding a single SMTC setting or information regarding multiple SMTC settings to the terminal. The network can transmit information regarding a single SMTC setting or information regarding multiple SMTC settings to the terminal through RRC signaling, for example, an RRC reset message (S740). The terminal can receive information regarding a single SMTC setting or information regarding multiple SMTC settings from the network. For example, the terminal can receive information regarding a single SMTC setting or information regarding multiple SMTC settings from the network through RRC signaling, for example, an RRC reset message.

[0119] Each of the SMTC settings may be associated with a reference location. For example, the reference location may be the center location of a cell or beam where the SSB is expected to be measured using the SMTC window determined by the corresponding SMTC setting at the terminal. However, the reference location may not be limited thereto. Each of the SMTC settings may include at least one of an SMTC identifier, a reference location (e.g., latitude and longitude coordinates, cell identifier, etc.), a reference SSB, or a timing window (e.g., start time, start offset, length, period, etc.).

[0120] The terminal can measure an SSB at a time (e.g., an SMTC window) according to a received SMTC setting and report the measurement results of the SSB to the network. The terminal can report the measurement results of the SSB to the network via a measurement report, for example, a measurement report message (S750). The network can receive the measurement results of the SSB from the terminal via a measurement report message. Alternatively, the terminal can measure SSBs at times according to multiple received SMTC setting information and report the measurement results of the SSBs to the network. The terminal can report the measurement results of the SSBs to the network via measurement reports, for example, measurement report messages. The network can receive the measurement results of the SSBs from the terminal via a measurement report message.

[0121] For example, a terminal can measure cell quality, such as SS-RSRP / SS-RSRQ / SS-SINR, from SSBs or SSBs within the SMTC window. The terminal can determine whether a measurement event is triggered based on the measurement results or the measurement results. If the terminal determines that a measurement event has been triggered, it can report the measurement results or the measurement results to the network. The network can receive the measurement results or the measurement results from the terminal. Based on the received measurement results or the measurement results, the network can perform mobility decisions such as handover / PSCell change / SCell activation. Accordingly, the terminal and the network can perform handover / PSCell change / SCell activation, etc.

[0122] As another example, a non-terrestrial network may apply a terminal location-based SMTC configuration method performed on the network side. In the terminal location-based SMTC configuration method performed on the network side, the maximum number of SMTC windows configured may not increase beyond the maximum number of existing SMTC mechanisms (for example, the maximum number of SMTC windows may be 4). The network may select a single SMTC configuration considering power consumption optimization. Alternatively, the network may select up to the maximum number of SMTC configurations that can be monitored simultaneously.

[0123] The network may request the terminal to report location information. The terminal may receive a request from the network to report its location information. In response to the network's request, the terminal may determine its location using positioning techniques such as GNSS or cell-based estimation. The terminal may report its determined location to the network. For example, the terminal may report its determined location to the network as terminal location information (e.g., UEPositioningInfo). The terminal may also report its determined location to the network via an extended RRC reset complete message (e.g., RRCReconfigurationComplete). The network may receive information regarding the terminal's location from the terminal. The location information may be latitude and longitude coordinates for the terminal's location. The location information may be cell ID-based relative location information. The location information may be the round-trip time (RTT) with the satellite.

[0124] The network can generate candidate SMTC configuration information. Each of the candidate SMTC configuration information may be associated with a reference location. For example, the reference location may be the center location of a cell or beam where the terminal is expected to measure the SSB using the SMTC window determined by the corresponding SMTC configuration. However, the reference location may not be limited to this.

[0125] A network can determine a reference location or a subset of reference locations based on the proximity of the terminal's current location received from the terminal and the reference locations. Proximity may refer to the distance between the terminal's current location and each of the reference locations. In this way, the network can determine a reference location with the shortest distance based on the distance between the terminal's current location and the reference locations. The network can determine a subset of reference locations based on the proximity of the terminal's current location (e.g., a location obtained through GNSS or cell-based estimation) and the reference locations.

[0126] The network can determine one SMTC setting from candidate SMTC settings by considering power consumption optimization based on information regarding a determined reference location or a subset of reference locations. The network can determine SMTC settings that can be simultaneously monitored by the terminal from candidate SMTC settings based on information regarding a determined reference location or a subset of reference locations.

[0127] The network can transmit a single SMTC setting or multiple SMTC settings to the terminal. The network can convey information regarding a single SMTC setting or multiple SMTC settings to the terminal through RRC signaling, for example, an RRC reset message. The terminal can receive information regarding a single SMTC setting or multiple SMTC settings from the network. For example, the terminal can receive information regarding a single SMTC setting or multiple SMTC settings from the network through RRC signaling, for example, an RRC reset message.

[0128] Each of the SMTC settings may be associated with a reference location. For example, the reference location may be the center location of a cell or beam where the SSB is expected to be measured using the SMTC window determined by the corresponding SMTC setting at the terminal. The reference location may not be limited thereto. Each of the SMTC settings may include at least one of an SMTC identifier, a reference location (e.g., latitude and longitude coordinates, cell identifier, etc.), a reference SSB, or a timing window (e.g., start time, start offset, length, period, etc.).

[0129] The terminal can measure SSBs at a time (e.g., an SMTC window) corresponding to a single received SMTC setting and report the measurement results of the SSBs to the network. The terminal can report the measurement results of the SSBs to the network via measurement reports, for example, through measurement report messages. The network can receive the measurement results of the SSBs from the terminal via measurement report messages. Alternatively, the terminal can measure SSBs at times corresponding to multiple received SMTC settings and report the measurement results of the SSBs to the network. The terminal can report the measurement results of the SSBs to the network via measurement reports, for example, through measurement report messages. The network can receive the measurement results of the SSBs from the terminal via measurement report messages.

[0130] As another example, the network may request the terminal to report location information. The terminal may receive a request from the network to report its location information. In response to the network's request, the terminal may determine its location using positioning techniques such as GNSS or cell-based estimation. Based on its determined location, the terminal may determine the propagation delay for the serving satellite and report information regarding the determined propagation delay to the network. The network may receive information regarding the propagation delay from the terminal.

[0131] The network can generate candidate SMTC configuration information. Each of the candidate SMTC configuration information may be associated with a reference location. For example, the reference location may be the center location of a cell or beam where the terminal is expected to measure the SSB using the SMTC window determined by the corresponding SMTC configuration. The reference location may not be limited to this. The network can determine the propagation delay for the satellite associated with the reference location at the reference location. The terminal can determine the time difference between the propagation delay for the serving satellite and the propagation delay for the satellite associated with the reference location.

[0132] The network can determine a single reference location or a subset of reference locations based on information regarding the determined time difference. In this way, the network can determine a single reference location with the shortest time difference based on the time difference in propagation delay between the terminal's current location and the reference locations. The network can determine a subset of reference locations based on the time difference between the terminal's current location and the reference locations.

[0133] The network can determine one SMTC setting from candidate SMTC settings by considering power consumption optimization based on information regarding a determined reference location or a subset of reference locations. The network can determine SMTC settings that can be simultaneously monitored by the terminal from candidate SMTC settings based on information regarding a determined reference location or a subset of reference locations.

[0134] The network can transmit a single SMTC setting or multiple SMTC settings to the terminal. The network can convey information regarding a single SMTC setting or multiple SMTC settings to the terminal through RRC signaling, for example, an RRC reset message. The terminal can receive information regarding a single SMTC setting or multiple SMTC settings from the network. For example, the terminal can receive information regarding a single SMTC setting or multiple SMTC settings from the network through RRC signaling, for example, an RRC reset message.

[0135] Each of the SMTC settings may be associated with a reference location. For example, the reference location may be the center location of a cell or beam where the SSB is expected to be measured using the SMTC window determined by the corresponding SMTC setting at the terminal. The reference location may not be limited thereto. Each of the SMTC settings may include at least one of an SMTC identifier, a reference location (e.g., latitude and longitude coordinates, cell identifier, etc.), a reference SSB, or a timing window (e.g., start time, start offset, length, period, etc.).

[0136] The terminal can measure SSBs at a time (e.g., an SMTC window) corresponding to a single received SMTC setting and report the measurement results of the SSBs to the network. The terminal can report the measurement results of the SSBs to the network via measurement reports, for example, through measurement report messages. The network can receive the measurement results of the SSBs from the terminal via measurement report messages. Alternatively, the terminal can measure SSBs at times corresponding to multiple received SMTC settings and report the measurement results of the SSBs to the network. The terminal can report the measurement results of the SSBs to the network via measurement reports, for example, through measurement report messages. The network can receive the measurement results of the SSBs from the terminal via measurement report messages.

[0137] The SMTC selection mechanism may not be limited to location-based SMTC selection methods and may include SSB index-based SMTC selection methods, RSRP-based SMTC selection methods, etc. In this regard, each selection method may have the following characteristics.

[0138] In location-based SMTC selection, each SMTC setting can be associated with a specific reference location and distance threshold. The terminal can calculate each reference location and distance based on its current location (e.g., GNSS measurement) and select and use an SMTC setting that falls within the distance threshold. The location-based SMTC selection method can accurately filter SMTC settings that are geographically highly relevant, improve measurement accuracy, and reduce power consumption.

[0139] In the RSRP-based SMTC selection method, the terminal can select the SMTC setting based on the RSRP measurement of each SSB. In an NTN environment, RSRP may not be a reliable indicator. RSRP variation can be minimal within a wide satellite beam. Signal profiles may be flat due to free-space propagation. Beam boundaries may be ambiguous, and coverage areas may overlap. For these reasons, it may be difficult for the terminal to select an accurate SMTC setting based on RSRP. Therefore, in an NTN environment, a location-based SMTC selection mechanism can complement the RSRP-based SMTC selection method. Alternatively, a location-based SMTC selection mechanism can replace the RSRP-based SMTC selection method. A location-based SMTC selection mechanism can be particularly useful for terminals in RRC idle or RRC disabled states.

[0140] As mentioned above, non-terrestrial networks can apply various SMTC selection methods. For example, non-terrestrial networks can apply a terminal-autonomous SMTC selection method based on RSRP. In the RSRP-based terminal-autonomous SMTC selection method, the terminal can autonomously select SMTC settings based on RSRP measurements. As another example, in the case of a location-based SMTC selection method, the terminal can select appropriate SMTC settings based on its geographical location. As yet another example, in an SSB-based SMTC selection method, the terminal can select a corresponding SMTC setting according to the SSB index received from the network.

[0141] As another example, non-terrestrial networks can apply a terminal assist information-based SMTC configuration method. In this terminal assist information-based SMTC configuration method, the network can configure optimal SMTC settings based on report information received from the terminal and provide the configured SMTC settings to the terminal. As yet another example, non-terrestrial networks can apply a method of linking multiple cell timings to a single SMTC setting. This method of linking multiple cell timings to a single SMTC setting enables the processing of multiple cell timings with a single SMTC setting.

[0142] These SMTC selection methods may exhibit different efficiencies depending on the characteristics of the NTN environment and the terminal state. For example, non-terrestrial networks can divide timing into two time intervals (e.g., T1, T2) and implement time / space distribution through regional allocation, thereby satisfying the Set 1-2 requirements based on 16 concurrently active beams with an SMTC list size of 4. As another example, a terminal can select two SMTC settings. In such cases, all SMTC selection methods can achieve minimal power saving effects.

[0143] In contrast, the terminal can select four or more SMTC settings. When four or more SMTC settings are selected, RSRP-based SMTC selection methods, location-based SMTC selection methods, and SSB-based SMTC selection methods can all demonstrate similar levels of power saving in idle / disabled mode. In connection mode, the number of SMTC settings may exceed four. In such cases, the terminal can report the selected SMTC settings to the network. Due to the overhead caused by this, some power saving effects may be lost. Additionally, beam-based SMTC selection methods may have less signal overhead and superior power efficiency compared to location-based methods.

[0144] Non-terrestrial networks can use an SSB-specific SMTC selection method that applies different SMTC settings per SSB in a beam-hopping environment. In the SSB-specific SMTC selection method, the network can analyze target cells or beam coverage and determine whether the structure transmits SSBs in a temporally distributed manner. In particular, in NTN environments or beam-hopping structures, the transmission timing may differ for each SSB. As a result, non-terrestrial networks may require the application of the SSB-specific SMTC selection method. In the SSB-specific SMTC selection method, the network can transmit multiple SMTC settings to the terminal via RRC messages.

[0145] Each of the multiple SMTC configurations can be mapped to be applied to a specific SSB. For example, an SMTC configuration (e.g., SMTC-ConfigList) may include at least one of the following information.

[0146] -SMTC Index

[0147] - An SSB index that specifies a particular SSB associated with an SMTC index

[0148] -SMTC Window (start time, start offset, length, etc.)

[0149] -periodicity

[0150] The SSB-specific SMTC selection method can use such SMTC settings. The SSB-specific SMTC selection method can set different SMTC windows for SSB #0 transmitted at 0ms, SSB #1 transmitted at 5ms, or SSB #2 transmitted at 10ms. The terminal can receive multiple SMTC settings from the network via RRC messages (e.g., RRCReconfiguration). The terminal can store the received multiple SMTC settings.

[0151] The terminal can determine the transmission period and window timing of the corresponding SSB for each of the multiple SMTC settings and can prepare to measure the SSB during the corresponding time period when necessary. The terminal can measure the SSB at a specified time according to the SMTC window corresponding to each of the multiple SMTC settings and can report the measured results to the network on a periodic or event-based basis.

[0152] The beam pattern may change. The terminal location may change significantly. In such cases, the network may generate a new SSB-specific SMTC configuration. The network may transmit the newly generated SSB-specific SMTC configuration to the terminal via an RRC configuration message (e.g., RRCReconfiguration) or an RRC configuration message containing a synchronization signal (e.g., RRCReconfigurationWithSync).

[0153] Existing NR-NTN can use an SMTC window adjustment mechanism to account for differences in propagation delay caused by multiple satellites. To support the SMTC window adjustment mechanism, the terminal can estimate its position by utilizing, for example, GNSS. In this regard, beam hopping technology can consider the following Case 1 and Case 2 adjacent cell scenarios to evaluate the necessity of such SMTC window adjustment.

[0154] In the Case 1 adjacent cell scenario, all adjacent cells may be formed by multiple beams of a single satellite. In the Case 2 adjacent cell scenario, some adjacent cells may be formed by beams of different satellites. In the Case 1 adjacent cell scenario, multiple SMTC settings for the adjacent beams of a single satellite may have a fixed window timing offset from the terminal's perspective. As a result, adjustment for each of the multiple SMTC settings may not be required.

[0155] Figure 8 is a conceptual diagram illustrating a serving cell and an adjacent cell in a multi-satellite environment.

[0156] Referring to FIG. 8, a serving cell (821) by a serving satellite (811) can provide service to a terminal (830). The serving cell (821) may have first to seventh adjacent cells (822, 823, 824, 825, 826, 827). Some fourth, fifth, and sixth adjacent cells (824, 825, 826) may be cells by the serving satellite. Other some third adjacent cells (823) may be cells by the adjacent satellite (812). Other some second and seventh adjacent cells (822, 827) may be cells by another adjacent satellite (813).

[0157] Figure 9 is a conceptual diagram illustrating propagation delay in a multi-satellite environment.

[0158] Referring to FIG. 9, unlike the Case 1 adjacent cell scenario, in the Case 2 adjacent cell scenario, the serving cell by the serving satellite may have adjacent cells by other satellites. In the Case 2 adjacent cell scenario, the SSBs of the cells of the same satellite may share the same serving propagation delay (PD). For example, the serving cell, the third adjacent cell, the fourth adjacent cell, and the fifth adjacent cell may have the same serving propagation delay. The second adjacent cell may have the first adjacent propagation delay. The first adjacent cell and the sixth adjacent cell may have the second adjacent propagation delay.

[0159] The serving satellite may transmit a first SSB toward the serving cell. The first SSB may reach the serving cell after passing through the serving propagation delay from the serving satellite after experiencing the serving propagation delay. The terminal may set the start time of the first SMTC window (SMTC 1) to the serving propagation delay. The terminal may receive the first SSB from the serving satellite using the first SMTC window. The terminal may perform a first measurement on the first SSB and report the result of the first measurement to the network. The network may receive the result of the first measurement from the terminal.

[0160] The second adjacent satellite may transmit the second SSB toward the first adjacent cell after the elapsed first offset. The second SSB may reach the first adjacent cell from the second adjacent satellite after experiencing the second adjacent propagation delay. The terminal may set the start time of the second SMTC window (SMTC 2) to the serving propagation delay and the first offset. As a result, the terminal cannot receive the second SSB from the second adjacent satellite using the second SMTC window. To receive the second SSB from the second adjacent satellite, the terminal may adjust the start time of the second SMTC window (SMTC 2) to the second adjacent propagation delay and the first offset. The terminal may receive the second SSB from the second adjacent satellite using the adjusted second SMTC window. The terminal may perform a second measurement on the second SSB and report the result of the second measurement to the network. The network may receive the result of the second measurement from the terminal.

[0161] The first adjacent satellite may transmit the third SSB toward the second adjacent cell after the elapsed second offset. The third SSB may reach the second adjacent cell from the first adjacent satellite after experiencing the first adjacent propagation delay. The terminal may set the start time of the third SMTC window (SMTC 3) to the serving propagation delay and the second offset. As a result, the terminal cannot receive the third SSB from the first adjacent satellite using the third SMTC window. To receive the third SSB from the first adjacent satellite, the terminal may adjust the start time of the third SMTC window (SMTC 3) to the first adjacent propagation delay and the second offset. The terminal may receive the third SSB from the first adjacent satellite using the adjusted third SMTC window. The terminal may perform a third measurement on the third SSB and report the result of the third measurement to the network. The network may receive the result of the third measurement from the terminal.

[0162] The serving satellite may transmit a fourth SSB toward a third adjacent cell after the third offset has elapsed. The fourth SSB may reach the third adjacent cell from the serving satellite after experiencing a serving propagation delay. The terminal may set the start time of the fourth SMTC window (SMTC 4) to the serving propagation delay and the third offset. As a result, the terminal may receive the fourth SSB from the serving satellite using the fourth SMTC window. The terminal may perform a fourth measurement on the fourth SSB and report the result of the fourth measurement to the network. The network may receive the result of the fourth measurement from the terminal.

[0163] The serving satellite may transmit a fifth SSB toward a fourth adjacent cell after the elapsed fourth offset. The fifth SSB may reach the fourth adjacent cell from the serving satellite after experiencing a serving propagation delay. The terminal may set the start time of the fifth SMTC window (SMTC 5) to the serving propagation delay and the fourth offset. As a result, the terminal may receive the fifth SSB from the serving satellite using the fifth SMTC window. The terminal may perform a fifth measurement on the fifth SSB and report the result of the fifth measurement to the network. The network may receive the result of the fifth measurement from the terminal.

[0164] The serving satellite may transmit the 6th SSB toward the 5th adjacent cell after the elapsed 5th offset. The 6th SSB may reach the 5th adjacent cell from the serving satellite after experiencing the serving propagation delay. The terminal may set the start time of the 6th SMTC window (SMTC 6) to the serving propagation delay and the 5th offset. As a result, the terminal may receive the 6th SSB from the serving satellite using the 6th SMTC window. The terminal may perform a 6th measurement on the 6th SSB and report the result of the 6th measurement to the network. The network may receive the result of the 6th measurement from the terminal.

[0165] The second adjacent satellite may transmit the seventh SSB toward the sixth adjacent cell after the elapsed sixth offset. The seventh SSB may reach the sixth adjacent cell from the second adjacent satellite after experiencing the second adjacent propagation delay. The terminal may set the start time of the seventh SMTC window (SMTC 7) to the serving propagation delay and the sixth offset. As a result, the terminal cannot receive the seventh SSB from the second adjacent satellite using the seventh SMTC window. To receive the seventh SSB from the second adjacent satellite, the terminal may adjust the start time of the seventh SMTC window (SMTC 7) to the second adjacent propagation delay and the sixth offset. The terminal may receive the seventh SSB from the second adjacent satellite using the adjusted seventh SMTC window. The terminal may perform a seventh measurement on the seventh SSB and report the result of the seventh measurement to the network. The network may receive the result of the seventh measurement from the terminal.

[0166] As such, in the Case 2 adjacent cell scenario, SSBs from different satellites may have different propagation delays. Consequently, the terminal may not be able to receive SSBs from adjacent cells without location-based SMTC window adjustment. Considering these characteristics, non-ground networks may omit SMTC window adjustment for adjacent beam-hopping cells of the serving satellite. Non-ground networks may apply SMTC window adjustment similar to existing NR-NTN to adjacent beam-hopping cells of other satellites. SMTC window adjustment can guarantee SSB reception at the terminal in a multi-satellite environment while reducing unnecessary computations. In particular, the necessity of SMTC window adjustment in a multi-satellite environment may vary depending on the source of the satellite from which the adjacent cells are formed.

[0167] Non-terrestrial networks can apply SMTC window adjustments separately in Case 1 and Case 2 adjacent cell scenarios. In the Case 1 adjacent cell scenario, multiple SMTC configurations for adjacent beams of a single satellite may have a fixed window timing offset from the terminal's perspective. In the Case 1 adjacent cell scenario, the propagation delay between SSBs originating from the same satellite may be nearly identical. Therefore, SMTC window adjustment may not be necessary in the Case 1 adjacent cell scenario. In the Case 2 adjacent cell scenario, SSB signals originating from different satellites may have different propagation delays. Therefore, location-based SMTC window adjustment may be required in the Case 2 adjacent cell scenario. Without location-based SMTC window adjustment, the terminal may not be able to properly receive adjacent cell SSBs from other satellites.

[0168] Therefore, non-terrestrial networks can omit SMTC window adjustment for adjacent beam-hopping cells of the serving satellite in a beam-hopping environment. It may be efficient for non-terrestrial networks to apply SMTC window adjustment to adjacent beam-hopping cells of other satellites in a manner similar to existing NTNs. This approach can have the advantage of guaranteeing SSB reception in a multi-satellite environment while reducing unnecessary computations. In this regard, non-terrestrial networks can apply a terminal-based SMTC window adjustment method in a satellite beam-hopping environment.

[0169] The terminal may attempt to measure at least one SSB in at least one adjacent cell of the serving cell. The network may transmit information about the adjacent cells to the terminal. For example, the network may transmit a System Information Block (SIB) containing information about the adjacent cells to the terminal. The terminal may receive information about the adjacent cells from the network. For example, the terminal may receive a System Information Block containing information about the adjacent cells from the network.

[0170] Information regarding adjacent cells may include the physical cell identifier (PCI) for each adjacent cell, the carrier frequency, auxiliary information regarding the satellite associated with the adjacent cell, etc. Auxiliary information regarding the satellite associated with the adjacent cell may include the satellite's position information (e.g., ephemeris).

[0171] The terminal can acquire its position via GNSS, etc., and can determine whether to apply SMTC window adjustment based on information about adjacent cells received from the network. The terminal can determine that the adjacent cell is a cell generated from the same satellite as the serving cell based on ephemeris of the adjacent cell. If the SMTC setting is for a cell generated from the same satellite as the serving cell, the terminal may not apply SMTC window adjustment. In other words, if the adjacent cell is formed by the same satellite as the serving cell, the terminal may maintain the default setting without applying an offset to the SMTC window.

[0172] In contrast, the terminal can determine that the adjacent cell is a cell generated by a satellite different from the serving cell based on ephemerals regarding the adjacent cell. The terminal can apply SMTC window adjustments if the adjacent cell from which it intends to measure SSB from the network is an adjacent cell generated by a satellite different from the serving cell's satellite. For example, the terminal can determine the difference in the estimated time of arrival of the SSB based on the terminal's location information and the orbit information of the other satellite. The terminal can determine an offset to apply the determined difference in the estimated time of arrival to the start period of the SMTC window. The terminal can adjust the SMTC window to reflect the determined offset and measure the SSB using the adjusted SMTC window. In this way, the offset can be dynamically determined based on the difference in propagation delay between the other satellite and the terminal, and can be applied to align the estimated time of arrival of the SSB with the SMTC window.

[0173] As another example, a terminal may attempt to measure at least one SSB from at least one adjacent cell of a serving cell. In such a case, in the SMTC window adjustment method by the terminal, the network may notify the terminal via RRC signaling whether the cell or beam to be measured is a cell or beam generated from the satellite of the serving cell. The terminal may receive a notification from the network via RRC signaling indicating whether the cell or beam to be measured is a cell or beam generated from the satellite of the serving cell.

[0174] In other words, the network can transmit information about the cell or beam to the terminal via RRC signaling when the cell or beam to be measured for SSB is a cell or beam generated from the satellite of the serving cell. The terminal can receive information about the cell or beam from the network via RRC signaling when the cell or beam to be measured for SSB is a cell or beam generated from the satellite of the serving cell.

[0175] The terminal can acquire its position through GNSS, etc., and can determine whether to apply SMTC window adjustment based on information about the cell or beam received from the network. If the SMTC setting is for a cell generated from the same satellite as the serving cell, the terminal may not apply SMTC window adjustment. Conversely, if the SMTC setting is for a cell generated from a satellite different from the satellite of the serving cell, the terminal may apply SMTC window adjustment.

[0176] The network may transmit adjacent cell (or adjacent satellite) information to the terminal, including satellite position information (e.g., ephemeris) for adjacent cells generated from the satellite of the serving cell and other satellites. The terminal may receive adjacent cell (or adjacent satellite) information from the network, including satellite position information (e.g., ephemeris) for adjacent cells generated from the satellite of the serving cell and other satellites. When applying SMTC window adjustment, the terminal may obtain satellite position information (e.g., ephemeris) for adjacent cells generated from the satellite of the serving cell and other satellites from the adjacent cell (or adjacent satellite) information received from the network.

[0177] For example, the terminal can determine the serving propagation delay between itself and a serving cell (or serving satellite) based on its own location. The terminal can determine the adjacent propagation delay between itself and an adjacent cell (or adjacent satellite) based on its own location. The terminal can determine the time difference between the serving propagation delay and the adjacent propagation delay. The terminal can adjust the SMTC window based on the determined time difference.

[0178] As another example, in a satellite beam-hopping environment, a non-terrestrial network may apply an SMTC window adjustment method by the network. The network may request the terminal to report location information. The terminal may receive a request from the network to report its location information. In response to the network's request, the terminal may determine its location using positioning techniques such as GNSS or cell-based estimation. The terminal may report its determined location to the network. For example, the terminal may report its determined location to the network as terminal location information (e.g., UEPositioningInfo). Alternatively, the terminal may report its determined location to the network through an extended RRC reset completion message (e.g., RRCReconfigurationComplete). The network may receive information regarding the terminal's location from the terminal. Alternatively, the terminal may report its determined location to the network through a location assist information message (e.g., LocationAssistanceInfo). The network may receive information regarding the terminal's location from the terminal.

[0179] The network can manage at least one of the ephemeris (or orbital information) or beam hopping schedules of each satellite. The network can track and determine, based on a schedule table, when and where each beam arrives based on at least one of the ephemeris (or orbital information) or beam hopping schedules of each satellite. Based on information regarding the terminal's location and the transmission times of the satellite beams, the network can calculate the estimated time for each SSB to arrive at the terminal. For example, SSB arrival time t rx can be calculated by the following mathematical formula 1. tx t can be the SSB transmission time, d can be the distance between the satellite and the terminal, and c can be the speed of light.

[0180]

[0181] The network can set the SMTC offset and SMTC duration based on the SSB arrival time. The network can include a time margin before and after the SSB arrival time in the SMTC offset. The network can set the duration to a measurement time length (e.g., 2 to 5 ms).

[0182] For example, the network can determine the estimated time of arrival difference of the SSB based on the terminal's location information and the orbit information of other satellites. The network can determine an offset to apply the determined estimated time of arrival difference to the start period of the SMTC window. The network can adjust the start time of the SMTC window by reflecting the determined offset.

[0183] The network may transmit SMTC configuration information to the terminal via RRC reset messages, etc. The terminal may receive SMTC configuration information from the network via RRC reset messages, etc. The SMTC configuration information may include at least one of an SMTC offset (e.g., an offset based on the arrival time of the SSB), an SMTC duration (e.g., a window length), or an SMTC periodicity (e.g., a repetition period). The terminal may measure the SSB during the SMTC window set by the SMTC configuration information. The terminal may utilize the measurement results for cell selection, beam selection, handover, etc.

[0184] SMTC settings or SMTC operation methods may vary depending on the terminal's RRC status. For example, in an RRC idle or RRC disabled state, the terminal can autonomously select and apply SMTC. In an RRC connected state, the network can control SMTC settings more directly. In this regard, non-terrestrial networks can set the SMTC cycle to be shorter than the SSB cycle in the RRC idle or RRC disabled state, thereby increasing flexibility. In the RRC idle or RRC disabled state, the terminal can select an appropriate SMTC and optimize power consumption by utilizing location-based auxiliary information received from the network.

[0185] In an RRC connection state, the terminal may use a single SMTC cycle. In such cases, the terminal's mobility performance may be degraded. The beam hopping pattern and SMTC timing may not align. In such cases, the terminal may fail to measure adjacent cells. Therefore, a more sophisticated SMTC configuration method may be required in connection mode.

[0186] Considering these characteristics, the ability to set different SMTC periods and offsets within the same frequency layer can be particularly important for terminals in an RRC connection state. This allows the network to provide the terminal with optimized measurement settings tailored to the terminal's location and beam hopping pattern. The terminal can receive these optimized measurement settings from the network. Such optimized measurement settings can contribute to improving the terminal's mobility performance.

[0187] The terminal can report location information to the network. The network can receive location information from the terminal. The network can determine SMTC settings optimized for the location and can provide the determined optimized SMTC settings to the terminal.

[0188] In the pre-configuration phase, the network (e.g., a base station (e.g., a gNB) or an NTN gateway) may pre-define multiple candidate SMTC configurations considering service coverage. Each of the multiple candidate SMTC configurations may include the following information.

[0189] - Reference location information

[0190] ■ Latitude and Longitude Coordinate Formats

[0191] -SSB transmission timing information

[0192] ■ Information about the frame / slot in which the SSB is transmitted, SSB transmission period, SSB transmission offset

[0193] ■ Measurement cycle, timing window start time and length

[0194] - Applicable regional scope or identifier (identifier, ID) (optional)

[0195] - Beam Hopping Schedule Information: Beam hopping schedule information may be pattern / table information regarding which beam (or cell) is turned on and transmitted at which time / interval on the time axis.

[0196] For example, a network can define different SMTC settings for regions communicating from the ground via satellite. For example, a network can define an SMTC setting, e.g., SMTC-A, for region A communicating from the ground via satellite. A network can define an SMTC setting, e.g., SMTC-B, for region B communicating from the ground via satellite. A network can define an SMTC setting, e.g., SMTC-C, for region C communicating from the ground via satellite. In the position reporting phase, a terminal can acquire its geographic location through GNSS or cell-based positioning technology. The terminal can express the acquired location as latitude / longitude or (x,y,z) coordinates. The terminal can transmit information about the acquired location to the network via an RRC message. The network can receive information about the acquired location from the terminal.

[0197] In the distance calculation and SMTC matching step on the network side, the network may determine the distance to each predefined reference location (e.g., Euclidean distance or Earth ellipsoid-based distance (e.g., Haversine distance)) based on the location of the received terminal. The network may determine one or more candidate SMTC settings corresponding to the reference location closest to the terminal location among the candidate SMTC settings. For example, the SMTC settings and distances may be as follows. The network may select and determine the SMTC-C that has the shortest distance between the terminal location and the reference location.

[0198] -SMTC-A(Reference Location-Busan): The distance between the terminal's location and the reference location is 330 km.

[0199] -SMTC-B(Reference Location-Daejeon): The distance between the terminal's location and the reference location is 140 km.

[0200] -SMTC-C(Reference Location-Seoul): The distance between the terminal's location and the reference location is 10km.

[0201] In the final SMTC setting determination and signaling stage, the network may determine the selected SMTC-C as the final SMTC setting for the terminal and signal the corresponding SMTC setting information to the terminal. The signaling method may be performed through an RRC reset message. The SMTC setting may include the following parameters. The terminal may receive the SMTC setting from the network.

[0202] - SMTC measurement period, SMTC window start offset, SMTC window length

[0203] In the terminal-side synchronization signal measurement step, the terminal can perform a measurement for receiving a synchronization signal block (e.g., SSB) based on the received SMTC settings. The arrival of the SSB can be anticipated within the SMTC window selected by the terminal. The terminal can perform effective synchronization without unnecessary standby or power consumption.

[0204] As another example, a network can signal multiple candidate reference locations and multiple candidate SMTC settings to a terminal. The terminal can receive multiple candidate reference locations and multiple candidate SMTC settings from the network through signaling. The terminal can acquire its own location through GNSS, etc. The terminal can determine priority information for the nearest reference location or reference locations based on its acquired location and at least one of the multiple candidate reference locations or candidate SMTC settings.

[0205] The terminal can feed back priority information regarding the nearest reference location or reference locations to the network. The network can receive priority information regarding the nearest reference location or reference locations from the terminal. Based on the nearest reference location received from the terminal, the network can select and determine one SMTC setting from multiple SMTC settings. The network can transmit information regarding the determined SMTC setting to the terminal. The terminal can measure the SSB according to the received SMTC setting and report the measurement result to the network. The network can receive the SSB measurement result from the terminal.

[0206] Alternatively, the network may select and determine multiple SMTC settings from multiple SMTC settings based on priority information regarding a reference location received from the terminal. The network may transmit information regarding the determined SMTC settings to the terminal. The terminal may measure SSBs according to the received SMTC settings and report the measurement results to the network. The network may receive the SSB measurement results from the terminal.

[0207] The terminal can autonomously select and use the SMTC setting most suitable for its location from among multiple candidate SMTC settings received in advance from the network. To this end, during the candidate SMTC setting and provision stage on the network side, the network may consider wide coverage and pre-define multiple candidate SMTC settings. The network may transmit multiple candidate SMTC settings to the terminal. The terminal may receive multiple candidate SMTC settings from the network. Each of the candidate SMTC settings may include the following information.

[0208] - Reference location information, SMTC window parameters (e.g., SSB measurement period, window start time, window length, etc.)

[0209] For example, the network can signal four candidate SMTC settings to the terminal as shown in Table 4.

[0210] SMTC ID Reference Location Measurement Period (ms) Start Time (ms) Window Length (ms) SMTC-1 Seoul 160 105 SMTC-2 Daejeon 160 155 SMTC-3 Busan 160 205 SMTC-4 Gwangju 160 255

[0211] In the terminal location acquisition stage, the terminal can determine its location in real time using GNSS or other positioning methods. For example, the terminal's location could be downtown Seoul at latitude 37.56 degrees and longitude 126.98 degrees. In the distance determination and priority determination stage, the terminal can determine the distance between the reference locations of candidate SMTC settings received from the network and its current location. For example, the terminal can obtain results as shown in Table 5 below through distance determination using the Haversine formula. The terminal can sort the candidate SMTC settings in order of distance and select one or two candidate SMTC settings closest to the terminal's current location. For example, the terminal can determine SMTC-1.

[0212] SMTC ID Distance (km) SMTC-12.1 SMTC-2140.0 SMTC-3330.0 SMTC-4270.0

[0213] In the step of performing SSB measurements based on a selected SMTC on the terminal side, the terminal can set an SMTC window based on the timing parameters of the determined SMTC-1, and can perform measurements to receive SSB during the SMTC window using the set SMTC window. Through this process, the terminal can avoid unnecessary reception waiting or seeking excluding the measurement window, reduce power consumption, and quickly synchronize with the network. As a variant embodiment, the terminal may apply a multiple SMTC setting selection and priority reporting method. In the multiple SMTC setting selection and priority reporting method, the terminal can select two or more candidate SMTC settings and manage priorities internally. In some cases, the terminal may feed back the selected reference location ID or priority to the network. The network may adjust the beam hopping schedule, etc., based on the reference location ID or priority received from the terminal. Alternatively, the network may optimize the beam hopping schedule, etc., based on the reference location ID or priority received from the terminal.

[0214] The SSB index-based SMTC autonomous selection method may be a method that allows the terminal to autonomously select the optimal SMTC setting by utilizing SSB index information received. In the SSB index-based SMTC autonomous selection method, the network may generate SMTC setting information mapped to each SSB index. The network may transmit the SMTC setting information mapped to each SSB index to the terminal. The network may broadcast the SMTC setting information corresponding to each SSB index (or beam ID) through RRC messages or system information blocks. The SMTC setting information may include SMTC timing information (start time, window length, period, etc.) for each SSB index.

[0215] The terminal can receive SMTC configuration information mapped by SSB index from the network. The terminal can receive at least one SSB in the cell where it is currently located. The terminal can determine the index of the SSB having the strongest received signal strength among the at least one received SSB. The terminal can apply the SMTC configuration information mapped to the determined SSB index.

[0216] In other words, the terminal can measure the SSB using an SMTC window based on SMTC configuration information matched to the determined SSB index, and report the SSB measurement results to the network. As a result, the terminal can avoid unnecessary SMTC window monitoring and reduce power consumption.

[0217] For example, the SSB index may change due to the terminal's position change. In other words, the index of the SSB with the strongest received signal strength received by the terminal may change due to the terminal's position change. Alternatively, the SSB index may change due to a change in the beam pattern. In other words, the index of the SSB with the strongest received signal strength received by the terminal may change due to a change in the beam pattern. The terminal can determine the converted SSB index. The terminal can apply SMTC configuration information mapped to the determined new SSB index.

[0218] The terminal can measure the SSB using an SMTC window based on SMTC configuration information matched to the index of the determined new SSB, and report the measurement results of the SSB to the network. This dynamic switching capability can enhance the adaptability of the terminal in NTN environments with various beam-hopping patterns.

[0219] In particular, the SSB index-based SMTC autonomous selection method can efficiently select SMTC settings on the terminal without a separate location measurement technology (e.g., GNSS). The SSB index-based SMTC autonomous selection method minimizes additional processing burden by utilizing the tasks that must be performed for SSB reception on the terminal.

[0220] A non-terrestrial network can correct the SMTC window by considering the difference in arrival times of synchronization signal blocks in a beam-hopping scenario where adjacent cells are formed by different satellites. To this end, in the step of determining the need for offset correction, the terminal or network can verify whether adjacent cells are formed by different satellites through RRC configuration information or beam schedule information, and can decide whether to make corrections based on the verification result.

[0221] - Case 1 Adjacent Cell Scenario (Same Satellite-Based Adjacent Cell)

[0222] ■ SSB propagation delays can be nearly identical across cells. Therefore, the terminal or network may decide that correction of the SMTC window is unnecessary.

[0223] - Case 2 Adjacent Cell Scenario (Multi-satellite-based Adjacent Cell)

[0224] ■ SSB propagation delays can vary across cells. Therefore, the terminal or network may determine that correction of the SMTC window is necessary.

[0225] The terminal can determine the satellite-specific propagation delay using at least one of the terminal's current location (e.g., obtained via GNSS), orbit information of each satellite (e.g., ephemeris), or the distance between the satellite and the terminal. The terminal can correct the start time of the SMTC window by delaying it by 1.0 ms as shown in Table 6 in order to receive SSB from an adjacent cell.

[0226] Target Cell SSB Estimated Time SMTC Window Start Period (Before Correction) SMTC Window Start Time (After Correction) Serving Cell (A) TO+4ms TO+3ms TO+3ms (No Change) Adjacent Cell (B) TO+5ms TO+3ms TO+4ms (+1ms Offset Applied)

[0227] In contrast, the network may determine the satellite-specific propagation delay using at least one of the terminal's current location, orbital information of each satellite (e.g., ephemeris), or the distance between the satellite and the terminal. The network may determine an offset to correct the start time of the SMTC window by delaying it in order to receive the SSB from an adjacent cell. The network may transmit information regarding the determined offset to the terminal. The terminal may receive information regarding the offset from the network and correct the start time of the SMTC window according to the received information regarding the offset. In the SSB reception and measurement phase, the terminal may reliably receive the SSB based on the corrected SMTC window and perform cell selection, handover, and measurement reporting based on the measurement results of the received SSB.

[0228] As a modified embodiment, the non-terrestrial network may consider a terminal-led method in which the terminal directly calculates the offset and applies it to the SMTC window, a network-led method in which a base station or satellite calculates the offset value and signals it to the terminal, and a hybrid method in which the network provides a reference value to the terminal and fine-tunes according to the environment based on the reference value received by the terminal.

[0229] Regarding cell access control mechanisms for downlink coverage enhancement (DL-CE), non-terrestrial networks may consider an explicit barring mechanism to control access of terminals supporting downlink coverage enhancement. The barring mechanism may be implemented by including a new field called cellBarredNTN-DL-CE in system information block 1 (SIB1).

[0230] For example, the 'cellBarredNTN-DL-CE' field can have a value of 'barred' or 'notBarred'. A 'barred' value may mean that the cell blocks connections from terminals that support DL-CE. On the other hand, a 'notBarred' value may mean that the cell allows connections from terminals that support downlink coverage improvement. The terminal may receive a system information block. The system information block received by the terminal may not contain the 'cellBarredNTN-DL-CE' field. In this case, the terminal may assume that the cell does not allow connections from terminals that support DL-CE.

[0231] In particular, even when both the existing 'cellBarred' and 'cellBarredNTN' are set to the 'barred' value, a terminal supporting DL-CE can ignore this 'barred' value and operate based on the value of the 'cellBarredNTN-DL-CE' field. As a result, a terminal supporting DL-CE can effectively access a cell with a downlink coverage enhancement function applied. Through this explicit barring mechanism, the terminal can clearly determine whether a cell is accessible without needing to monitor additional system information blocks other than SIB1, thereby reducing the burden on the terminal.

[0232] According to the present disclosure, the network can obtain the following technical effects by utilizing the location information of the terminal to select and provide the synchronization signal measurement timing setting to a minimum.

[0233] - Minimize device power consumption

[0234] ■ The terminal may not receive or process all pre-configured candidate SMTC settings, and may receive some SMTC settings optimized for its location. As a result, the power efficiency of the terminal can be improved due to a reduction in signal processing burden and computational load.

[0235] - Improved signal reception success rate

[0236] ■ An appropriate SMTC timing window can be set based on location. As a result, the terminal can receive SSBs with high accuracy at that location. The terminal can receive SSBs with high accuracy and improve initial synchronization and cell search success rates.

[0237] - Improve network resource efficiency

[0238] ■ The network may not provide the same SMTC settings to all terminals. The network may provide SMTC settings differentially based on location. Terminals can operate SSB and measurement resources more precisely and efficiently.

[0239] - Securing flexibility in responding to location privacy

[0240] ■ The terminal may not directly provide location coordinates to the network. The terminal may report a reference location ID close to its own location to the network. As a result, non-terrestrial networks can flexibly apply location-based SMTC configuration methods in environments requiring location privacy protection.

[0241] - Provides scalability and flexibility of application

[0242] ■ The method of the present disclosure can be extended and applied to various location-dependent network environments, such as beamforming-based ground networks, drone networks, and fixed wireless access (FWA), in addition to NTN.

[0243] ■ The method of the present disclosure may be operated by combining terminal-led or network-led methods depending on the system structure or terminal function level.

[0244] According to the present disclosure, a terminal can receive a plurality of candidate SMTC settings from a network. The terminal can autonomously select an appropriate SMTC setting based on its location, thereby obtaining the following technical effects.

[0245] - Improved terminal power efficiency

[0246] ■ The terminal may not measure SSBs collectively across the entire candidate SMTC window, but may select some SMTC settings corresponding to the reference location closest to its own location to perform measurements. As a result, the terminal can reduce unnecessary measurement attempts and reception waiting times, and reduce power consumption.

[0247] - Ensure fast and stable synchronization performance

[0248] ■ An appropriate timing window can be set based on location. The terminal can improve the reception success rate of synchronization signal blocks. As a result, the terminal can reduce initial connection time and improve cell search performance.

[0249] - Reduce network load

[0250] ■ The network may not request or determine real-time location information on a per-terminal basis, and may provide up to seven SMTC settings defined collectively. As a result, the network can reduce RRC signaling complexity and system processing burden.

[0251] - Ensuring terminal autonomy and scalability

[0252] ■ The terminal can automatically select SMTC settings based on location. As a result, the terminal can flexibly adapt to various terrains, satellite orbits, and situations involving changes in terminal location.

[0253] - Simple implementation and excellent standard compatibility

[0254] ■ The method of the present disclosure can be based on the structure discussed in 3GPP RAN2 and can be easily implemented within the existing RRC message structure, so it can be efficient from the perspective of standardization and implementation.

[0255] According to the present disclosure, a non-ground network can provide an offset adjustment mechanism to resolve the problem of failure to receive synchronization signals that may occur in a multi-satellite-based beam-hopping scenario in an NR-NTN environment. As a result, the non-ground network can achieve the following technical effects.

[0256] - Improvement in synchronization signal reception rate

[0257] ■ In the case of adjacent cells formed by different satellites, the arrival time of the SSB may differ due to orbital differences between the satellites.

[0258] ■ The present disclosure can predict the difference in propagation delay of each satellite by utilizing terminal location and satellite orbit information, and can apply an accurate offset to the SMTC window based on this. As a result, the terminal can receive SSB without omission.

[0259] - Precise calibration possible without unnecessary window expansion

[0260] ■ Conventional methods cannot account for differences in propagation delay, which may result in setting a wide SMTC window or enabling multiple settings. However, according to the present disclosure, window correction can be precisely targeted only at the necessary times, thereby reducing resource waste and power consumption.

[0261] - Ensuring dynamic adaptability to differences in propagation delay between satellites

[0262] ■ Non-ground networks can dynamically adjust offsets in real time according to changes in satellite orbits or terminal location movements. As a result, non-ground networks can flexibly respond to various temporal and spatial situations.

[0263] - Supports both terminal-driven and network-driven methods

[0264] ■ The network can determine the offset and provide the determined offset to the terminal. Alternatively, the terminal can determine the offset independently. In this way, the non-terrestrial network can flexibly provide implementation methods depending on the network structure and the terminal performance level.

[0265] - Improvement of NR-NTN operational stability based on beam hopping

[0266] ■ In a multi-satellite environment, the terminal can reliably receive SSB. As a result, the terminal can achieve effects such as reduced initial connection failure rates, improved cell measurement accuracy, and ensured handover stability.

[0267] The methods according to the present invention may be implemented in the form of program instructions that can be executed through various computer means and recorded on a computer-readable medium. The computer-readable medium may include program instructions, data files, data structures, etc., either alone or in combination. The program instructions recorded on the computer-readable medium may be those specifically designed and configured for the present invention, or they may be those known and available to those skilled in the art of computer software.

[0268] Examples of computer-readable media include hardware devices specifically configured to store and execute program instructions, such as ROM, RAM, and flash memory. Examples of program instructions include machine code, such as that produced by a compiler, as well as high-level language code that can be executed by a computer using an interpreter, etc. The aforementioned hardware devices may be configured to operate as at least one software module to perform the operation of the present invention, and vice versa.

[0269] The operation of the method according to an embodiment of the present disclosure can be implemented as a computer-readable program or code on a computer-readable recording medium. A computer-readable recording medium includes all types of recording devices in which information that can be read by a computer system is stored. Additionally, the computer-readable recording medium may be distributed across networked computer systems, allowing the computer-readable program or code to be stored and executed in a distributed manner.

[0270] In addition, computer-readable recording media may include hardware devices specifically configured to store and execute program instructions, such as ROM, RAM, and flash memory. Program instructions may include machine code, such as that generated by a compiler, as well as high-level language code that can be executed by a computer using an interpreter, etc.

[0271] Some aspects of the present disclosure have been described in the context of a device, but may also be described according to a corresponding method, wherein a block or device corresponds to a method step or a feature of a method step. Similarly, aspects described in the context of a method may also be described according to a corresponding block or item or a feature of a corresponding device. Some or all of the method steps may be performed by (or using) a hardware device, such as, for example, a microprocessor, a programmable computer, or an electronic circuit. In some embodiments, at least one of the most important method steps may be performed by such a device.

[0272] In the embodiments, a programmable logic device (e.g., a field-programmable gate array) may be used to perform some or all of the functions of the methods described herein. In the embodiments, the field-programmable gate array may operate with a microprocessor to perform one of the methods described herein. Generally, it is preferable that the methods be performed by some hardware device.

[0273] Although the present disclosure has been described with reference to preferred embodiments, those skilled in the art will understand that various modifications and changes can be made to the present disclosure without departing from the spirit and scope of the present disclosure as set forth in the following claims.

Claims

1. As a method of a terminal, A step of receiving SMTC (synchronization signal measurement timing configuration) settings containing information about a reference location from a non-ground base station; A step of determining at least one SMTC setting based on the proximity of the terminal to the reference locations of the SMTC settings; and A method comprising the step of receiving at least one synchronization signal block (SSB) based on at least one SMTC setting, Method of the terminal.

2. In Claim 1, Each of the above SMTC settings further includes at least one of information regarding the SSB measurement period, information regarding the start time of the SMTC window, information regarding the length of the SMTC window, or information regarding the cell identifier. Method of the terminal.

3. In Claim 1, The step of determining at least one SMTC setting based on the proximity of the terminal to the reference locations of the SMTC settings is: A step of determining information regarding the location of the above terminal; A step of determining the distance between the above location and each of the above reference locations; and A step comprising determining at least one SMTC setting from the SMTC settings based on the distance above, Method of the terminal.

4. In Claim 3, The step of determining information regarding the location of the above terminal is, A step comprising determining information about the location of the terminal using at least one of a GNSS (global navigation satellite system), cell-based estimation, or position measurement sensor, Method of the terminal.

5. In Claim 3, The information regarding the above location is at least one of information regarding latitude and longitude coordinates, cell ID (identifier)-based relative location information, or information regarding round-trip propagation delay with a non-ground base station. Method of the terminal.

6. In Claim 1, The step of receiving at least one SSB based on the above at least one SMTC setting is, A step of determining whether the target cell associated with the above at least one SMTC setting is a cell set by the above non-ground base station; and The method further includes the step of adjusting the start time of the SMTC window of the at least one SMTC setting based on the fact that the target cell is not the cell set by the non-ground base station. Method of the terminal.

7. In Claim 1, The step of receiving at least one synchronization signal block (SSB) based on the above at least one SMTC setting is, A step of receiving a notification from the non-ground base station that the target cell associated with the above at least one SMTC setting is a cell set by the non-ground base station different from the above non-ground base station; and A step further comprising adjusting the start time of the SMTC window of at least one SMTC setting, Method of the terminal.

8. As a method of a non-ground base station, A step of generating candidate SMTC settings including information on reference locations for the terminal's serving cell and adjacent cells; A step of transmitting information about reference locations for the above serving cell and the above adjacent cells to a terminal; A step of requesting a reference location from the above terminal; A step of receiving information about at least one reference location among the reference locations from the terminal; and The method includes the step of determining at least one SMTC setting from the candidate SMTC settings based on information regarding at least one reference location, The above at least one reference location is determined based on the proximity of the terminal and each of the reference locations, and the proximity is the distance between the location of the terminal and each of the reference locations, Non-ground base station method.

9. In Claim 8, The above at least one SMTC setting further includes at least one of information regarding the SSB measurement cycle, information regarding the start time of the SMTC window, information regarding the length of the SMTC window, or information regarding the cell identifier. Non-ground base station method.

10. In Claim 8, A step of transmitting at least one SMTC setting to the terminal; A step of transmitting at least one SSB based on the above at least one SMTC setting; and The method further comprises the step of receiving a measurement result for the at least one SSB from the terminal. Non-ground base station method.

11. In Claim 8, A step of determining whether each of the above adjacent cells is a cell set by the above non-ground base station; and The method further comprises the step of adjusting the start time of an SMTC window included in the candidate SMTC setting of a first adjacent cell, which is a cell set by the non-ground base station among the adjacent cells. Non-ground base station method.

12. As a terminal, It includes at least one processor, and the at least one processor is the terminal, Receive SMTC (synchronization signal measurement timing configuration) settings containing information about a reference location from a non-ground base station; Determining at least one SMTC setting based on the proximity of the terminal to the reference locations of the above SMTC settings; and Causing to receive at least one SSB (synchronization signal block) based on the above at least one SMTC setting, Terminal.

13. In Claim 12, Each of the above SMTC settings further includes at least one of information regarding the SSB measurement period, information regarding the start time of the SMTC window, information regarding the length of the SMTC window, or information regarding the cell identifier. Terminal.

14. In Claim 12, In order to determine at least one SMTC setting based on the proximity of the terminal to the reference locations of the above SMTC settings, the at least one processor, the terminal, Determining information regarding the location of the above terminal; Determine the distance between the above location and each of the above reference locations; and Causing to determine at least one SMTC setting among the SMTC settings based on the above distance, Terminal.

15. In Claim 12, In order to receive at least one SSB based on the above at least one SMTC setting, the at least one processor, the terminal, Determining whether the target cell associated with the above at least one SMTC setting is a cell set by the above non-ground base station; and Further causing to adjust the start time of the SMTC window of the at least one SMTC setting based on the fact that the above target cell is not the cell set by the above non-ground base station, Terminal.

16. In Claim 12, In order to receive at least one SSB based on the above at least one SMTC setting, the at least one processor, the terminal, The non-ground base station receives a notification that the target cell associated with the above-mentioned at least one SMTC setting is a cell set by a non-ground base station different from the above-mentioned non-ground base station; and Further causing to adjust the start time of the SMTC window of at least one of the above SMTC settings, Terminal.

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