Method and device for configuring timing group for handover in non-terrestrial network

Abstract

Disclosed are a method and device for configuring a timing group for handover in a non-terrestrial network. The method performed by a user equipment (UE) may comprise the steps of: receiving timing group configuration information for a timing group including the UE from a first satellite on the basis of a beam spot supported by the first satellite; receiving a handover command message including timing information about the UE from the first satellite according to a timing group index included in the timing group configuration information; acquiring timing advance (TA) information using the timing information; and transmitting a handover completed message using the TA information.

Description

Method and device for setting up timing groups for handover in non-terrestrial networks

[0001] The present disclosure relates to a technique for setting up a group for handover in a non-terrestrial network, and more particularly, to a technique for setting up a timing group in a RACH-less (Random Access Channel-less) handover.

[0002] When a handover procedure is performed in a terrestrial or non-terrestrial network, the Timing Advance (TA) of the source cell may be different from the TA of the target cell. In this case, if the UE does not know the TA value of the target cell during the handover procedure, the UE may obtain the TA value of the target cell through a random access procedure. The process of the UE obtaining the TA value of the target cell through the random access procedure may cause a delay in the handover procedure. To reduce the delay in the handover procedure, a RACH-less (Random Access Channel-less) handover may be proposed in the terrestrial network. In this case, the target base station may transmit information on the timing difference of the TA of the target cell to the UE. In addition, the source base station may transmit information on the timing difference of the TA of the source cell to the UE.

[0003] In a terrestrial network environment, handover procedures can be triggered by the movement of terminals. Therefore, it may be appropriate for the base station to control timing through individual signaling to each terminal.

[0004] In a non-terrestrial network environment, handover procedures can primarily occur due to satellite movement. Furthermore, in a non-terrestrial network environment, handover procedures can occur simultaneously or at similar times for a large number of terminals. A large number of handover procedures can result in a large number of random access procedures. These large number of random access procedures can result in signaling overhead. In a non-terrestrial network environment, a RACH-less handover procedure can reduce the signaling load and signaling delay caused by these large number of random access procedures. However, signaling overhead can occur when timing control signaling is performed on a per-terminal basis in a non-terrestrial network environment. In a non-terrestrial network, a large number of terminals can request handovers from a base station simultaneously or at similar times. Therefore, the present disclosure can configure timing information required for a RACH-less handover procedure by grouping terminals with similar timing information.

[0005] Groups with similar timing information can reduce signaling overhead because signaling is performed on a group-by-group basis. Therefore, the present disclosure can propose a method for establishing groups with similar timing information in situations requiring a feeder link switch, an earth fixed beam (EFB) environment, or an earth moving beam (EMB) environment.

[0006] The purpose of the present disclosure to solve the above problems is to provide a method and device for setting a timing group for handover in a non-terrestrial network.

[0007] In order to achieve the above object, a method of a UE (User Equipment) according to a first embodiment of the present disclosure may include a step of receiving timing group setting information for a timing group including the UE from a first satellite based on a beam spot supported by the first satellite, a step of receiving a handover command message including timing information of the UE from the first satellite according to a timing group index included in the timing group setting information, a step of obtaining TA (Timing Advance) information using the timing information, and a step of transmitting a handover completion message using the TA information.

[0008] The timing group setting information may include a timing group index for identifying the timing group including UEs within the first TA range when a difference value between the timing value of the UE and the timing value for the center position of the set distance value defined by the base station associated with the first satellite falls within the first TA range set by the base station.

[0009] The timing group setting information may include a timing group index for identifying the timing group including UEs within a distance range set by the base station from a center position of the beam area, when the UE falls within the distance range set by the base station.

[0010] The timing group setting information may include a timing group index for identifying the timing group including UEs having a cell remaining time within a time range set by the first satellite, when the cell remaining time, which is the time during which communication service for the beam area is provided to the UE, falls within the time range set by the first satellite.

[0011] The step of obtaining TA information using the timing information may include the step of obtaining TA information using a timing difference value corresponding to a difference between a first path including a path between the first satellite and a path between the first satellite and a base station at a central location of the timing group and a second path including a path between the second satellite and a path between the second satellite and a base station at a central location of the timing group.

[0012] The step of obtaining TA information using the timing information may include a step of the UE determining a UE-specific TA value on its own, and a step of updating a TA value for the UE using at least one of the UE-specific TA value, a common TA value equally applied to all UEs of a source cell included in the timing information, a common TA value equally applied to all UEs of a target cell, or a timing difference value due to a difference in RP (Reference Point) between the source cell and the target cell to obtain the TA information.

[0013] The step of obtaining TA information using the timing information may include the step of receiving at least one of the location information of the UE, the location information of the first satellite, or the satellite astronomy information from the first satellite, the step of calculating a timing adjustment value for the UE using at least one of the location information of the UE, the location information of the first satellite, and the satellite astronomy information, and the step of obtaining the TA information using the timing adjustment value and the timing information.

[0014] In order to achieve the above object, a method of a base station according to a second embodiment of the present disclosure may include a step of setting timing group setting information for a timing group including a UE (User Equipment) based on a beam spot supported by a first satellite, a step of transmitting a handover command message including timing information for the timing group to which the UE belongs to, to the UE, based on a timing group index included in the timing group setting information, and a step of receiving a handover completion message from the UE that has performed a handover procedure through the timing information for the timing group to which the UE belongs.

[0015] The step of setting the timing group setting information may include a step of setting the UE to the timing group when a difference value between the timing value of the UE and the timing value for the center position of the set distance value defined by the base station communicating through the first satellite is equal to or less than a second TA value defined by the base station for the timing group.

[0016] The step of setting the timing group setting information may include a step of setting the UE to the timing group when the cell remaining time, which is the time during which communication service for the beam area is provided to the UE, falls within a time range set by the first satellite.

[0017] The timing information may include at least one of a common TA value that is applied equally to all UEs of the source cell included in the timing information, a common TA value that is applied equally to all UEs of the target cell, or a timing difference value due to a difference in RP (Reference Point) between the source cell and the target cell.

[0018] According to a third embodiment of the present disclosure for achieving the above object, a UE includes at least one processor, and the at least one processor can cause the UE to receive timing group setting information for a timing group in which the UE is included from the first satellite based on a beam spot supported by the first satellite, receive a handover command message including timing information of the UE from the first satellite according to a timing group index included in the timing group setting information, acquire TA (Timing Advance) information using the timing information, and transmit a handover completion message using the TA information.

[0019] The timing group setting information may be configured to include a timing group index for identifying the timing group including UEs within the first TA range when a difference value between the timing value of the UE and the timing value for the center position of the set distance value defined by the base station associated with the first satellite falls within the first TA range set by the base station.

[0020] The timing group setting information may be caused to include the timing group index for identifying the timing group including UEs within a distance range set by the base station from the center position of the beam area, when the UE falls within the distance range.

[0021] The timing group setting information may be configured to include a timing group index for identifying the timing group including UEs having a cell remaining time within a time range set by the first satellite, when the cell remaining time, which is the time during which communication service for the beam area is provided to the UE, falls within the time range set by the first satellite.

[0022] When obtaining TA information using the timing information, the at least one processor may cause the UE to obtain TA information using a timing difference value corresponding to a difference between a first path including a path between the first satellite and a path between the first satellite and a base station at a central location of the timing group and a second path including a path between the second satellite and a path between the second satellite and a base station at a central location of the timing group.

[0023] In the case of obtaining TA information using the timing information, the at least one processor may cause the UE to determine a UE-specific TA value on its own, and update the TA value for the UE using at least one of the UE-specific TA value, a common TA value equally applied to all UEs of a source cell included in the timing information, a common TA value equally applied to all UEs of a target cell, or a timing difference value due to a difference in RP (Reference Point) between the source cell and the target cell, thereby obtaining the TA information.

[0024] In the case of obtaining TA information using the timing information, the at least one processor may cause the UE to receive at least one of the location information of the UE, the location information of the first satellite, or the satellite astronomy information from the first satellite, calculate a timing adjustment value for the UE using at least one of the location information of the UE, the location information of the first satellite, and the satellite astronomy information, and obtain the TA information using the timing adjustment value and the timing information.

[0025] According to the present disclosure, to enable coexistence between non-terrestrial and terrestrial communication networks, a non-terrestrial network (NTN) and a terrestrial network (TN) can share the same frequency. The non-terrestrial and terrestrial networks can provide services in the same area using the same frequency. Since signaling is performed in groups of terminals with similar timing information for handover procedures in the non-terrestrial network, signaling overhead can be reduced.

[0026] Figure 1a is a conceptual diagram illustrating embodiments of a non-terrestrial network.

[0027] Figure 1b is a conceptual diagram illustrating embodiments of a non-terrestrial network.

[0028] Figure 2a is a conceptual diagram illustrating embodiments of a non-terrestrial network.

[0029] Figure 2b is a conceptual diagram illustrating embodiments of a non-terrestrial network.

[0030] Figure 2c is a conceptual diagram illustrating embodiments of a non-terrestrial network.

[0031] Figure 3 is a block diagram illustrating embodiments of communication nodes constituting a non-terrestrial network.

[0032] Figure 4 is a block diagram illustrating embodiments of communication nodes that perform communication.

[0033] Figure 5a is a block diagram illustrating embodiments of a transmission path.

[0034] Figure 5b is a block diagram illustrating embodiments of a receiving path.

[0035] FIG. 6a is a conceptual diagram illustrating embodiments of a protocol stack of a user plane in a non-terrestrial network based on transparent payload.

[0036] FIG. 6b is a conceptual diagram illustrating embodiments of a protocol stack of a control plane in a non-terrestrial network based on transparent payload.

[0037] FIG. 7a is a conceptual diagram illustrating embodiments of a protocol stack of a user plane in a non-terrestrial network based on regenerative payload.

[0038] FIG. 7b is a conceptual diagram illustrating embodiments of a protocol stack of a control plane in a non-terrestrial network based on regenerative payload.

[0039] Figure 8 is a conceptual diagram illustrating embodiments of a non-terrestrial network.

[0040] Figure 9 is a conceptual diagram illustrating embodiments of an uplink time synchronization procedure.

[0041] Figure 10a is a conceptual diagram illustrating embodiments of a handover procedure.

[0042] Figure 10b is a conceptual diagram illustrating embodiments of a handover procedure.

[0043] Figure 11 is a conceptual diagram illustrating examples of beam footprints in an EFB environment.

[0044] Figure 12 is a conceptual diagram illustrating embodiments of EMB (earth moving beam).

[0045] Figure 13a is a conceptual diagram illustrating embodiments of a handover procedure in a non-terrestrial network.

[0046] Figure 13b is a conceptual diagram illustrating embodiments of a handover procedure in a non-terrestrial network.

[0047] FIG. 14a is a conceptual diagram illustrating embodiments of a feeder link switch environment.

[0048] Figure 14b is a conceptual diagram illustrating embodiments of a feeder link switch environment.

[0049] Figure 15 is a conceptual diagram illustrating embodiments of timing group settings.

[0050] Figure 16 is a conceptual diagram illustrating embodiments of a handover procedure in an EMB environment.

[0051] Figure 17 is a conceptual diagram illustrating embodiments of a handover procedure in an EMB environment.

[0052] Figure 18 is a flowchart illustrating embodiments of a handover procedure in an EMB environment.

[0053] This disclosure may be subject to various modifications and various embodiments. Specific embodiments are illustrated and described in detail in the drawings. However, this is not intended to limit the disclosure to specific embodiments, but rather to encompass all modifications, equivalents, and alternatives falling within the spirit and technical scope of the disclosure.

[0054] While terms such as "first" and "second" may be used to describe various components, these components should not be limited by these terms. These terms are used solely to distinguish one component from another. For example, without departing from the scope of the present disclosure, a first component could be referred to as a "second component," and similarly, a second component could also be referred to as a "first component." The term "and / or" may refer to a combination of multiple related items described herein or to any of multiple related items described herein.

[0055] In the present disclosure, “at least one of A and B” may mean “at least one of A or B” or “at least one of combinations of one or more of A and B.” Furthermore, in the present disclosure, “at least one of A and B” may mean “at least one of A or B” or “at least one of combinations of one or more of A and B.”

[0056] In the present disclosure, (re)transmission may mean “transmission,” “retransmission,” or “transmission and retransmission,” (re)setting may mean “setting,” “resetting,” or “setting and resetting,” (re)connection may mean “connection,” “reconnection,” or “connection and reconnection,” and (re)connection may mean “connection,” “reconnection,” or “connection and reconnection.”

[0057] When a component is referred to as being "connected" or "connected" to another component, it should be understood that it may be directly connected or connected to that other component, but that there may be other components intervening. Conversely, when a component is referred to as being "directly connected" or "connected" to another component, it should be understood that there are no other components intervening.

[0058] The terminology used in this disclosure is only used to describe specific embodiments and is not intended to limit the present disclosure. The singular expression includes the plural expression unless the context clearly indicates otherwise. In this disclosure, it should be understood that the terms "comprises" or "has" indicate the presence of a feature, number, step, operation, component, part, or combination thereof described in the specification, but do not preclude the presence or addition of one or more other features, numbers, steps, operations, components, parts, or combinations thereof.

[0059] Unless otherwise defined, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by a person of ordinary skill in the art to which this disclosure pertains. Terms defined in commonly used dictionaries should be interpreted as having a meaning consistent with their meaning in the context of the relevant technology, and shall not be interpreted in an idealized or overly formal sense unless explicitly defined herein.

[0060] 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 in describing the present disclosure, the same reference numerals will be used for identical components in the drawings, and redundant descriptions of identical components will be omitted. In addition to the embodiments explicitly described in the present disclosure, operations may be performed according to combinations of embodiments, extensions of embodiments, and / or modifications of embodiments. The performance of some operations may be omitted, and the order of operation may be changed.

[0061] In an embodiment, even if a method (e.g., transmitting or receiving a signal) performed by a first communication node among communication nodes is described, a corresponding second communication node can perform a method (e.g., receiving or transmitting a signal) corresponding to the method performed by the first communication node. That is, if an operation of a user equipment (UE) is described, a corresponding base station can perform an operation corresponding to the operation of the UE. Conversely, if an operation of a base station is described, a corresponding UE can perform an operation corresponding to the operation of the base station. In a non-terrestrial network (NTN) (e.g., a payload-based NTN), an operation of a base station can mean an operation of a satellite, and an operation of a satellite can mean an operation of a base station.

[0062] A base station may be referred to as a NodeB, an evolved NodeB, a gNodeB (next generation node B), a gNB, a device, an apparatus, a node, a communication node, a BTS (base transceiver station), a RRH (radio remote head), a TRP (transmission reception point), a RU (radio unit), an RSU (road side unit), a radio transceiver, an access point, an access node, etc. A UE may be referred to as a terminal, a device, an apparatus, a node, a communication node, an end node, an access terminal, a mobile terminal, a station, a subscriber station, a mobile station, a portable subscriber station, an OBU (on-broad unit), etc.

[0063] In the present disclosure, signaling may be at least one of upper layer signaling, MAC signaling, or PHY (physical) signaling. A message used for upper layer signaling may be referred to as an “upper layer message” or an “upper layer signaling message.” A message used for MAC signaling may be referred to as a “MAC message” or a “MAC signaling message.” A message used for PHY signaling may be referred to as a “PHY message” or a “PHY signaling message.” Upper layer signaling may refer to a transmission and reception operation of system information (e.g., a master information block (MIB), a system information block (SIB)) and / or an RRC message. MAC signaling may refer to a transmission and reception operation of a MAC control element (CE). PHY signaling may refer to a transmission and reception operation of control information (e.g., downlink control information (DCI), uplink control information (UCI), sidelink control information (SCI)).

[0064] In the present disclosure, “an operation (e.g., a transmission operation) is set” may mean that “setting information for the operation (e.g., an information element, a parameter)” and / or “information instructing the performance of the operation” is signaled. “An information element (e.g., a parameter) is set” may mean that the information element is signaled. In the present disclosure, “a signal and / or a channel” may mean a signal, a channel, or “a signal and a channel,” and a signal may be used to mean “a signal and / or a channel.”

[0065] The communication system may include at least one of a terrestrial network, a non-terrestrial network, a 4G communication network (e.g., a long-term evolution (LTE) communication network), a 5G communication network (e.g., a new radio (NR) communication network), or a 6G communication network. Each of the 4G communication network, the 5G communication network, and the 6G communication network may include a terrestrial network and / or a non-terrestrial network. The non-terrestrial network may operate based on at least one communication technology among the LTE communication technology, the 5G communication technology, and the 6G communication technology. The non-terrestrial network may provide communication services in various frequency bands.

[0066] The communication network to which the embodiment is applied is not limited to what is described below, and the embodiment may be applied to various communication networks (e.g., 4G communication networks, 5G communication networks, and / or 6G communication networks). Here, the communication network may be used in the same sense as the communication system.

[0067] Figure 1a is a conceptual diagram illustrating embodiments of a non-terrestrial network.

[0068] Referring to FIG. 1A, a non-terrestrial network may include a satellite (110), a communication node (120), a gateway (130), a data network (140), etc. The unit including the satellite (110) and the gateway (130) may be a remote radio unit (RRU). The non-terrestrial network illustrated in FIG. 1A may be a transparent payload-based non-terrestrial network. The satellite (110) may be a low Earth orbit (LEO) satellite, a medium Earth orbit (MEO) satellite, a geostationary Earth orbit (GEO) satellite, a high elliptical orbit (HEO) satellite, or an unmanned aircraft system (UAS) platform. The UAS platform may include a high altitude platform station (HAPS). The non-GEO satellite may be a LEO satellite and / or a MEO satellite.

[0069] The communication node (120) may include a communication node located on the ground (e.g., a UE, terminal) and a communication node located off the ground (e.g., an airplane, a 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 be referred to as an NTN payload. The gateway (130) may support multiple NTN payloads. The satellite (110) may provide a communication service to the communication node (120) using one or more beams. The shape of the reception range (footprint) of the beam of the satellite (110) may be elliptical or circular.

[0070] In non-terrestrial networks, three types of service links can be supported:

[0071] - Earth-fixed: The service link may be provided by beam(s) that continuously cover the same geographic area at all times (e.g., Geosynchronous Orbit (GSO) satellites).

[0072] - Quasi-earth-fixed: The service link may be provided by beam(s) that cover one geographic area for a limited period and another geographic area for another period (e.g., NGSO (non-GSO) satellites that produce steerable beams).

[0073] - Earth-moving: The service link may be provided by beam(s) moving over the Earth's surface (e.g., NGSO satellites producing fixed beams or non-steerable beams).

[0074] The communication node (120) can perform communication (e.g., downlink communication, uplink communication) with the satellite (110) using 4G communication technology, 5G communication technology, and / or 6G communication technology. Communication between the satellite (110) and the communication node (120) can be performed using an NR-Uu interface and / or a 6G-Uu interface. When DC (dual connectivity) is supported, the communication node (120) can be connected to not only the satellite (110) but also other base stations (e.g., base stations supporting 4G functions, 5G functions, and / or 6G functions), and can perform DC operations based on technologies defined in the 4G standard, the 5G standard, and / or the 6G standard.

[0075] 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 a NR-Uu interface, a 6G-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 4G communication technology, 5G communication technology, and / or 6G communication 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 may be performed based on a NG-C / U interface or a 6G-C / U interface.

[0076] As in the embodiment of Fig. 1b below, in a non-terrestrial network based on transparent payload, a base station and a core network may exist between a gateway (130) and a data network (140).

[0077] Figure 1b is a conceptual diagram illustrating embodiments of a non-terrestrial network.

[0078] Referring to FIG. 1B, a gateway may be connected to a base station, the base station may be connected to a core network, and the core network may be connected to a data network. Each of the base station and the core network may support 4G communication technology, 5G communication technology, and / or 6G communication technology. Communication between the gateway and the base station may be performed based on a NR-Uu interface or a 6G-Uu interface, and communication between the base station and the core network (e.g., AMF, UPF, SMF) may be performed based on a NG-C / U interface or a 6G-C / U interface.

[0079] Figure 2a is a conceptual diagram illustrating embodiments of a non-terrestrial network.

[0080] Referring to FIG. 2A, the non-terrestrial network may include satellite #1 (211), satellite #2 (212), communication node (220), gateway (230), data network (240), etc. The non-terrestrial network illustrated in FIG. 2A may be a regenerative payload-based non-terrestrial network. For example, each of satellite #1 (211) and satellite #2 (212) may perform a regenerative operation (e.g., a demodulation operation, a decoding operation, a re-encoding operation, a re-modulation operation, and / or a filtering operation) on a payload received from another entity constituting the non-terrestrial network (e.g., a communication node (220), a gateway (230)) and transmit the regenerated payload.

[0081] Each of satellite #1 (211) and satellite #2 (212) may be a LEO satellite, MEO satellite, GEO satellite, HEO satellite, or UAS platform. The UAS platform may include 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) frequency or an optical band. The ISL may be configured as optional. The communication node (220) may include a ground-based communication node (e.g., a UE, terminal) and a non-ground-based communication node (e.g., an airplane, a drone). A service link (e.g., a wireless link) may be established between satellite #1 (211) and the communication node (220). Satellite #1 (211) may be referred to as an NTN payload. Satellite #1 (211) can provide communication services to a communication node (220) using one or more beams.

[0082] The communication node (220) can perform communication (e.g., downlink communication, uplink communication) with satellite #1 (211) using 4G communication technology, 5G communication technology, and / or 6G communication technology. Communication between satellite #1 (211) and the communication node (220) can be performed using an NR-Uu interface or a 6G-Uu interface. When DC is supported, the communication node (220) can be connected to not only satellite #1 (211) but also other base stations (e.g., base stations supporting 4G functions, 5G functions, and / or 6G functions), and can perform DC operations based on technologies defined in the 4G standard, the 5G standard, and / or the 6G standard.

[0083] 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. Communication between each of satellite #1 (211) and satellite #2 (212) and the gateway (230) may be performed based on an NR-Uu interface, a 6G-Uu interface, or an SRI. The gateway (230) may be connected to a data network (240).

[0084] As in the embodiments of FIGS. 2b and 2c below, a “core network” may exist between the gateway (230) and the data network (240).

[0085] FIG. 2b is a conceptual diagram illustrating embodiments of a non-terrestrial network, and FIG. 2c is a conceptual diagram illustrating embodiments of a non-terrestrial network.

[0086] Referring to FIGS. 2B and 2C, a gateway may be connected to a core network, and the core network may be connected to a data network. The core network may support 4G communication technology, 5G communication technology, and / or 6G communication technology. For example, the core network may include AMF, UPF, SMF, etc. Communication between the gateway and the core network may be performed based on an NG-C / U interface or a 6G-C / U interface. The function of a base station may be performed by a satellite. That is, a base station may be located on a satellite. Payloads may be processed by a base station located on a satellite. Base stations located on different satellites may be connected to the same core network. A single satellite may have one or more base stations. In the non-terrestrial network of FIG. 2B, an ISL between satellites may not be established, and in the non-terrestrial network of FIG. 2C, an ISL between satellites may be established.

[0087] Meanwhile, entities (e.g., satellites, base stations, UEs, communication nodes, gateways, etc.) constituting the non-terrestrial network illustrated in FIGS. 1a, 1b, 2a, 2b, and / or 2c may be configured as follows. In the present disclosure, entities may be referred to as communication nodes.

[0088] Figure 3 is a block diagram illustrating embodiments of communication nodes constituting a non-terrestrial network.

[0089] Referring to FIG. 3, a communication node (300) may include at least one processor (310), a memory (320), and a transmission / reception device (330) that is connected to a network and performs communication. In addition, the communication node (300) may further include an input interface device (340), an output interface device (350), a storage device (360), etc. Each component included in the communication node (300) may be connected by a bus (370) and communicate with each other.

[0090] However, each component included in the communication node (300) may be connected through an individual interface or individual bus centered around the processor (310), rather than a common bus (370). For example, the processor (310) may be connected to at least one of a memory (320), a transmission / reception device (330), an input interface device (340), an output interface device (350), or a storage device (360) through a dedicated interface.

[0091] The processor (310) can execute program commands stored in at least one of the memory (320) and the storage device (360). The processor (310) may refer to a central processing unit (CPU), a graphics processing unit (GPU), or a dedicated processor in which the methods according to the embodiments are performed. Each of the memory (320) and the storage device (360) may be configured with at least one of a volatile storage medium or a non-volatile storage medium. For example, the memory (320) may be configured with at least one of a read-only memory (ROM) or a random access memory (RAM).

[0092] Meanwhile, communication nodes performing communication in a communication network (e.g., a non-terrestrial network) may be configured as follows. The communication node illustrated in FIG. 4 may be a specific embodiment of the communication node illustrated in FIG. 3.

[0093] Figure 4 is a block diagram illustrating embodiments of communication nodes that perform communication.

[0094] Referring to FIG. 4, each of the first communication node (400a) and the second communication node (400b) may be a base station or a UE. The first communication node (400a) may transmit a signal to the second communication node (400b). The transmission processor (411) included in the first communication node (400a) may receive data (e.g., a data unit) from a data source (410). The transmission processor (411) may receive control information from a controller (416). The control information may include at least one of system information, RRC configuration information (e.g., information configured by RRC signaling), MAC control information (e.g., MAC CE), or PHY control information (e.g., DCI, SCI).

[0095] The transmitting processor (411) may perform a processing operation on data (e.g., an encoding operation, a symbol mapping operation, etc.) to generate data symbol(s). The transmitting processor (411) may perform a processing operation on control information (e.g., an encoding operation, a symbol mapping operation, etc.) to generate control symbol(s). In addition, the transmitting processor (411) may generate synchronization / reference symbol(s) for a synchronization signal and / or a reference signal.

[0096] The Tx MIMO processor (412) may perform spatial processing operations (e.g., precoding operations) on data symbol(s), control symbol(s), and / or synchronization / reference symbol(s). An output (e.g., a symbol stream) of the Tx MIMO processor (412) may be provided to modulators (MODs) included in the transceivers (413a to 413t). The modulators (MODs) may perform processing operations on the symbol streams to generate modulation symbols, and may perform additional processing operations (e.g., analog conversion operations, amplification operations, filtering operations, upconversion operations) on the modulation symbols to generate signals. The signals generated by the modulators (MODs) of the transceivers (413a to 413t) may be transmitted via the antennas (414a to 414t).

[0097] Signals transmitted by the first communication node (400a) may be received by antennas (464a to 464r) of the second communication node (400b). Signals received by the antennas (464a to 464r) may be provided to demodulators (DEMODs) included in transceivers (463a to 463r). The demodulator (DEMOD) may perform a processing operation (e.g., a filtering operation, an amplification operation, a downconversion operation, a digital conversion operation) on the signal to obtain samples. The demodulator (DEMOD) may perform an additional processing operation on the samples to obtain symbols. The MIMO detector (462) may perform a MIMO detection operation on the symbols. The receiving processor (461) may perform a processing operation (e.g., a deinterleaving operation, a decoding operation) on the symbols. The output of the receiving processor (461) may be provided to a data sink (460) and a controller (466). For example, data may be provided to the data sink (460) and control information may be provided to the controller (466).

[0098] Meanwhile, the second communication node (400b) can transmit a signal to the first communication node (400a). The transmitting processor (468) included in the second communication node (400b) can receive data (e.g., data units) from a data source (467) and perform a processing operation on the data to generate data symbol(s). The transmitting processor (468) can receive control information from the controller (466) and perform a processing operation on the control information to generate control symbol(s). In addition, the transmitting processor (468) can perform a processing operation on a reference signal to generate reference symbol(s).

[0099] The Tx MIMO processor (469) may perform spatial processing operations (e.g., precoding operations) on data symbol(s), control symbol(s), and / or reference symbol(s). The output (e.g., symbol stream) of the Tx MIMO processor (469) may be provided to modulators (MODs) included in the transceivers (463a to 463t). The modulators (MODs) may perform processing operations on the symbol streams to generate modulation symbols, and may perform additional processing operations (e.g., analog conversion operations, amplification operations, filtering operations, upconversion operations) on the modulation symbols to generate signals. The signals generated by the modulators (MODs) of the transceivers (463a to 463t) may be transmitted via the antennas (464a to 464t).

[0100] Signals transmitted by the second communication node (400b) may be received by the antennas (414a to 414r) of the first communication node (400a). The signals received by the antennas (414a to 414r) may be provided to demodulators (DEMODs) included in the transceivers (413a to 413r). The demodulator (DEMOD) may perform a processing operation (e.g., a filtering operation, an amplification operation, a downconversion operation, a digital conversion operation) on the signal to obtain samples. The demodulator (DEMOD) may perform an additional processing operation on the samples to obtain symbols. The MIMO detector (420) may perform a MIMO detection operation on the symbols. The receiving processor (419) may perform a processing operation (e.g., a deinterleaving operation, a decoding operation) on the symbols. The output of the receiving processor (419) may be provided to a data sink (418) and a controller (416). For example, data may be provided to the data sink (418) and control information may be provided to the controller (416).

[0101] Memories (415 and 465) can store data, control information, and / or program code. Scheduler (417) can perform scheduling operations for communication. Processors (411, 412, 419, 461, 468, 469) and controllers (416, 466) illustrated in FIG. 4 may be the processor (310) illustrated in FIG. 3 and may be used to perform the methods described in the present disclosure.

[0102] FIG. 5a is a block diagram illustrating embodiments of a transmission path, and FIG. 5b is a block diagram illustrating embodiments of a reception path.

[0103] Referring to FIGS. 5A and 5B, a transmission path (510) may be implemented in a communication node that transmits a signal, and a reception path (520) may be implemented in a communication node that receives a signal. The transmission path (510) may include a channel coding and modulation block (511), a serial-to-parallel (S-to-P) block (512), an Inverse Fast Fourier Transform (N IFFT) block (513), a parallel-to-serial (P-to-S) block (514), a cyclic prefix (CP) addition block (515), and an up-converter (UC) (516). The receiving path (520) may include a DC (down-converter) (521), a CP removal block (522), an S-to-P block (523), an N FFT block (524), a P-to-S block (525), and a channel decoding and demodulation block (526). Here, N may be a natural number.

[0104] In the transmission path (510), information bits may be input to a channel coding and modulation block (511). The channel coding and modulation block (511) may perform a coding operation (e.g., a low-density parity check (LDPC) coding operation, a polar coding operation, etc.) and a modulation operation (e.g., a quadrature phase shift keying (QPSK), a quadrature amplitude modulation (QAM), etc.) on the information bits. The output of the channel coding and modulation block (511) may be a sequence of modulation symbols.

[0105] The S-to-P block (512) can convert modulation symbols in the frequency domain into parallel symbol streams to generate N parallel symbol streams. N can be an IFFT size or an FFT size. The N IFFT block (513) can perform an IFFT operation on the N parallel symbol streams to generate signals in the time domain. The P-to-S block (514) can convert the output (e.g., parallel signals) of the N IFFT block (513) into a serial signal to generate a serial signal.

[0106] The CP addition block (515) can insert a CP into a signal. The UC (516) can up-convert the frequency of the output of the CP addition block (515) to an RF (radio frequency) frequency. Additionally, the output of the CP addition block (515) can be filtered at the baseband before up-conversion.

[0107] A signal transmitted from a transmission path (510) may be input to a reception path (520). An operation in the reception path (520) may be the reverse operation of the operation in the transmission path (510). A DC (521) may down-convert the frequency of the received signal to a baseband frequency. A CP removal block (522) may remove a CP from a signal. The output of the CP removal block (522) may be a serial signal. An S-to-P block (523) may convert the serial signal into parallel signals. An N FFT block (524) may perform an FFT algorithm to generate N parallel signals. A P-to-S block (525) may convert the parallel signals into a sequence of modulation symbols. A channel decoding and demodulation block (526) may perform a demodulation operation on the modulation symbols and perform a decoding operation on the result of the demodulation operation to restore data.

[0108] In FIGS. 5A and 5B , Discrete Fourier Transform (DFT) and Inverse DFT (IDFT) may be used instead of FFT and IFFT. Each of the blocks (e.g., components) in FIGS. 5A and 5B may be implemented by at least one of hardware, software, or firmware. For example, some of the blocks in FIGS. 5A and 5B may be implemented by software, and the remaining blocks may be implemented by hardware or a “combination of hardware and software.” In FIGS. 5A and 5B , a single block may be subdivided into multiple blocks, multiple blocks may be integrated into a single block, some blocks may be omitted, and blocks supporting other functions may be added.

[0109] Meanwhile, NTN reference scenarios can be defined as shown in Table 1 below.

[0110] NTN shown in Fig. 1 NTNGEO shown in Fig. 2 Scenario A Scenario BLEO (steerable beam) Scenario C1 Scenario D1 LEO (beam moving with satellite) Scenario C2 Scenario D2

[0111] In the non-terrestrial network illustrated in FIG. 1a and / or FIG. 1b, if the satellite (110) is a GEO satellite (e.g., a GEO satellite supporting transparent functionality), this may be referred to as “Scenario A.” In the non-terrestrial network illustrated in FIG. 2a, FIG. 2b, and / or FIG. 2c, if each of satellite #1 (211) and satellite #2 (212) is a GEO satellite (e.g., a GEO supporting regeneration functionality), this may be referred to as “Scenario B.”

[0112] If the satellite (110) in the non-terrestrial network illustrated in FIG. 1a and / or FIG. 1b is a LEO satellite having steerable beams, this may be referred to as “Scenario C1.” If the satellite (110) in the non-terrestrial network illustrated in FIG. 1a and / or FIG. 1b is a LEO satellite having beams move with the satellite, this may be referred to as “Scenario C2.” If each of satellite #1 (211) and satellite #2 (212) in the non-terrestrial network illustrated in FIG. 2a, FIG. 2b, and / or FIG. 2c is a LEO satellite having steerable beams, this may be referred to as “Scenario D1.” In the non-terrestrial network illustrated in FIG. 2a, FIG. 2b, and / or FIG. 2c, if each of satellite #1 (211) and satellite #2 (212) is a LEO satellite having beams that travel with the satellite, this may be referred to as “Scenario D2.”

[0113] Parameters for the NTN reference scenarios defined in Table 1 can be defined as shown in Table 2 below.

[0114] Scenario A and B Scenario C and D Altitude 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 capability (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 round trip delay (RTD) (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) - 41.77 ms (1200 km altitude) Scenario D: (Regeneration payload: only service link) - 12.89 ms (600 km altitude) - 20.89 ms (1200 km altitude) Maximum differential delay within a cell 10.3 ms 3.12 ms (600 km altitude) 3.18 ms (1200 km altitude) Service link NR or 6G Feeder link 3GPP or non-3GPP defined radio interface

[0115] Additionally, in the NTN reference scenario defined in Table 1, the delay constraint can be defined as shown in Table 3 below.

[0116] Scenario A Scenario B Scenario C1-2 Scenario D1-2 Satellite altitude 35,786 km 600 km Maximum RTD on the air interface between the base station and the UE 541.75 ms (worst case) 270.57 ms 28.41 ms 12.88 ms Minimum RTD on the air interface between the base station and the UE 477.14 ms 238.57 ms 8 ms 4 ms

[0117] FIG. 6a is a conceptual diagram illustrating embodiments of a protocol stack of a user plane in a non-terrestrial network based on transparent payload, and FIG. 6b is a conceptual diagram illustrating embodiments of a protocol stack of a control plane in a non-terrestrial network based on transparent payload.

[0118] Referring to FIGS. 6A and 6B, user data may be transmitted and received between a UE and a core network (e.g., UPF), and control data (e.g., control information) may be transmitted and received between a UE and a core network (e.g., AMF). Each of the user data and the control data may be transmitted and received via a satellite and / or a gateway. The protocol stack of the user plane illustrated in FIG. 6A may be applied identically or similarly to a 6G communication network. The protocol stack of the control plane illustrated in FIG. 6B may be applied identically or similarly to a 6G communication network.

[0119] FIG. 7a is a conceptual diagram illustrating embodiments of a protocol stack of a user plane in a non-terrestrial network based on regenerative payloads, and FIG. 7b is a conceptual diagram illustrating embodiments of a protocol stack of a control plane in a non-terrestrial network based on regenerative payloads.

[0120] Referring to FIGS. 7A and 7B , user data and control data (e.g., control information) may be transmitted and received through an interface between a UE and a satellite (e.g., a base station). User data may refer to a user protocol data unit (PDU). The protocol stack of the satellite radio interface (SRI) may be used to transmit and receive user data and / or control data between the satellite and the gateway. User data may be transmitted and received through a GTP (GPRS (general packet radio service) tunneling protocol)-U tunnel between the satellite and the core network.

[0121] Meanwhile, in a non-terrestrial network, a base station may transmit system information (e.g., SIB19) containing satellite assistance information for NTN access. A UE may receive system information (e.g., SIB19) from the base station, verify the satellite assistance information included in the system information, and perform communication (e.g., non-terrestrial communication) based on the satellite assistance information. SIB19 may include the information element(s) defined in Table 4 below.

[0122] SIB19-r17 ::= SEQUENCE {ntn-Config-r17 NTN-Config-r17t-Service-r17 INTEGER(0..549755813887)referenceLocation-r17 ReferenceLocation-r17distanceThresh-r17 INTEGER(0..65525)ntn-NeighCellConfigList-r17 NTN-NeighCellConfigList-r17lateNonCriticalExtension OCTET STRING...,[[ntn-NeighCellConfigListExt-v1720 NTN-NeighCellConfigList-r17]]}NTN-NeighCellConfigList-r17 ::= SEQUENCE (SIZE(1..maxCellNTN-r17)) OF NTN-NeighCellConfig-r17NTN-NeighCellConfig-r17 ::= SEQUENCE {ntn-Config-r17 NTN-Config-r17carrierFreq-r17 ARFCN-ValueNRphysCellId-r17 PhysCellId}

[0123] NTN-Config defined in Table 4 may include information element(s) defined in Table 5 below.

[0124] NTN-Config-r17 ::= SEQUENCE { epochTime-r17 EpochTime-r17ntn-UlSyncValidityDuration-r17 ENUMERATED{ s5, s10, s15, s20, s25, s30, s35, s40, s45, s50, s55, s60, s120, s180, s240, s900}cellSpecificKoffset-r17 INTEGER(1..1023)kmac-r17 INTEGER(1..512)ta-Info-r17 TA-Info-r17ntn-PolarizationDL-r17 ENUMERATED {rhcp,lhcp,linear}ntn-PolarizationUL-r17 ENUMERATED {rhcp,lhcp,linear}ephemerisInfo-r17 EphemerisInfo-r17ta-Report-r17 ENUMERATED {enabled}...}EpochTime-r17 ::= SEQUENCE {sfn-r17 INTEGER(0..1023),subFrameNR-r17 INTEGER(0..9)}TA-Info-r17 ::= SEQUENCE {ta-Common-r17 INTEGER(0..66485757),ta-CommonDrift-r17 INTEGER(-257303..257303)ta-CommonDriftVariant-r17 INTEGER(0..28949)}

[0125] EphemerisInfo defined in Table 5 may contain the information element(s) defined in Table 6 below.

[0126] EphemerisInfo-r17 ::= CHOICE {positionVelocity-r17 PositionVelocity-r17,orbital-r17 Orbital-r17}PositionVelocity-r17 ::= SEQUENCE {positionX-r17 PositionStateVector-r17,positionY-r17 PositionStateVector-r17,positionZ-r17 PositionStateVector-r17,velocityVX-r17 VelocityStateVector-r17,velocityVY-r17 VelocityStateVector-r17,velocityVZ-r17 VelocityStateVector-r17}Orbital-r17 ::= SEQUENCE {semiMajorAxis-r17 INTEGER (0..8589934591),eccentricity-r17 INTEGER (0..1048575),periapsis-r17 INTEGER (0..268435455),longitude-r17 INTEGER (0..268435455),inclination-r17 INTEGER (-67108864..67108863),meanAnomaly-r17 INTEGER (0..268435455)}PositionStateVector-r17 ::= INTEGER (-33554432..33554431)VelocityStateVector-r17 ::= INTEGER (-131072..131071)

[0127] In a handover procedure in a terrestrial or non-terrestrial network environment, the required source cell TA and target cell TA (Timing Advance) may be different. If the UE does not know the TA value of the target cell during the handover procedure, the UE can obtain the TA value of the target cell through a random access procedure. Therefore, the UE can perform a system information acquisition procedure, an initial timing information prediction procedure, and a fine tuning procedure through preamble transmission, similar to the procedure for initial access to a cell in the idle state (RRC_IDLE). If the UE performs a fine tuning procedure through this procedure, the handover of the UE may be delayed. To reduce the handover delay, the UE can perform a RACH (Random Access Channel)-less handover procedure in the terrestrial network. In a RACH-less handover procedure, the UEs can individually receive information about the timing difference between the TA of the target cell and the TA of the source cell. In a terrestrial network environment, handovers can occur due to terminal movement. Therefore, timing control in terrestrial networks can be achieved through individual signaling for each terminal.

[0128] In a non-terrestrial network environment, handovers can occur primarily due to satellite movement. Therefore, handovers can occur simultaneously or at similar times for a large number of terminals in a non-terrestrial network environment. In this case, RACH-less handover can be proposed to reduce signaling load and / or signaling delay in a non-terrestrial network environment. The TA values ​​of the source cell and the target cell may differ. Therefore, for a RACH-less handover procedure, the source base station can transmit timing information of the target cell to terminals in the source cell. The source base station can transmit the target cell timing information to the terminals before the terminals in the source cell initiate the handover procedure. In a terrestrial network environment, handovers can occur individually for each terminal. In a terrestrial network, handovers can occur at distributed times. On the other hand, in a non-terrestrial network environment, handover procedures can be initiated by a large number of terminals. At this time, many terminals can request handover procedures from the same target satellite. Therefore, in a non-terrestrial network environment, handover procedures can occur simultaneously or at approximately the same time. For example, in an EFB environment, terminals within the same beamspot can request a handover procedure to the same target satellite at the same or similar time. In an EMB environment, terminals within a satellite's beamspot can continuously request a handover procedure to the target satellite according to the satellite's movement. Therefore, in an EMB environment, handover procedures can be distributed and occur at various times. Furthermore, unlike handovers in a TN environment, which are triggered by the individual movements of terminals, handover procedures in an EMB environment can be triggered by satellites that move in a relatively fixed pattern.

[0129] In a non-terrestrial network environment, signaling for individual handovers for each terminal can result in a high signaling load. Therefore, to efficiently handle RACH-less handovers in a non-terrestrial network environment, satellites can transmit timing information through group-based signaling. Group-based signaling can reduce handover signaling load.

[0130] Satellites can group terminals with similar timing information to utilize group-based signaling. Signaling for groups with similar timing information can reduce signaling overhead because signaling is performed on a group-by-group basis. Therefore, the present disclosure proposes a method for grouping similar timing information in situations requiring a feeder link switch, an earth fixed beam (EFB) environment, or an earth moving beam (EMB) environment.

[0131] Figure 8 is a conceptual diagram illustrating embodiments of a non-terrestrial network.

[0132] Referring to FIG. 8, a satellite may perform a method for improving uplink time and uplink frequency synchronization for a New Radio (NR) non-terrestrial network. A terminal may perform a method for controlling timing in a Radio Resource Control (RRC) idle state (RRC_IDLE) or an RRC activated state (RRC_INACTIVE). The terminal may obtain initial timing information by utilizing system information and GNSS functions for calculating a common TA (Common TA) provided by the satellite. The terminal may obtain the initial TA before transmitting a Physical Random Access Channel (PRACH) preamble to the satellite. For uplink (UL) timing synchronization of the terminal, a timing error may need to occur within half of the preamble cyclic prefix (CP). The timing error may refer to a timing error after pre-compensating for a delay before the initial RACH (Random Access Channel) preamble transmission.

[0133] The present disclosure may propose an open-loop timing advance (TA) scheme including a common TA and a UE-specific TA in a NR NTN. The common TA may vary over time. The network may calculate a common TA value. Furthermore, the network may transmit the common TA value to a UE. The UE may estimate and predict the common TA over time according to defined rules using the transmitted common TA parameters. The UE-specific TA may refer to a TA estimated by the UE itself to pre-compensate for service link delay. The positions of the satellite and the UE may be transmitted to the UE for the TA estimated by the UE.

[0134] NR non-terrestrial networks may differ from 5G NR in the presence or absence of open-loop TA and related parameters (i.e., common TA parameters and satellite ephemeris information). To enable UEs to access the network in RRC IDLE or RRC INACTIVE state, open-loop TA parameters may be included in a System Information Block (SIB) message. The open-loop TA parameters may include information about a synchronization signal and a Physical Broadcast Channel (PBCH) block (SSB) period (e.g., 20 ms or more). The validity period of the common TA parameters and satellite ephemeris information may be set by the base station. In NR non-terrestrial networks, UEs may perform a procedure for uplink time synchronization. The procedure for uplink time synchronization may be expressed as follows.

[0135] Figure 9 is a conceptual diagram illustrating embodiments of an uplink time synchronization procedure.

[0136] Referring to Figure 9, a base station can transmit an SSB to a terminal (S910). The SSB can include at least one of DL time information, DL frequency, and synchronization information. The terminal can receive the SSB transmitted by the base station.

[0137] The base station can transmit data to the terminal via CORESET#0 (Control Resource Set #0) (S920). CORESET#0 may refer to physical resources used to carry PDCCH / DCI. In other words, CORESET#0 may refer to a special type of CORESET used to carry PDCCH / DCI for SIB. SIB detection information may include at least one of PRACH resources, common TA parameters, satellite celestial information, and absolute time information. The terminal can receive physical resources from the base station via CORESET#0.

[0138] The UE can use the common TA included in the SIB. The UE can estimate a UE-specific TA. The UE can use the estimated UE-specific TA for the preamble.

[0139] The terminal can transmit message 1 (Msg.1) or message A (Msg.A) to the base station (S930). Message 1 (Msg.1) or message A (Msg.A) can include a preamble. The base station can receive message 1 (Msg.1) or message A (Msg.A) transmitted by the terminal.

[0140] The base station can transmit message 2 (Msg.2) or message B (Msg.B) to the base station (S940). Message 2 (Msg.2) or message B (Msg.B) can include a random access preamble (RAR) message. The RAR can include a timing advance command (TAC) field. The terminal can receive message 2 (Msg.2) or message B (Msg.B) transmitted by the base station.

[0141] For uplink synchronization, the terminal may use at least one of the common TA included in the SIB, the UE-specific TA, or the TAC included in the RAR.

[0142] In the RRC connection state, the terminal and the base station can perform the following procedures. The base station can transmit a MAC CE containing a TAC to the terminal (S950). The terminal can receive the TAC transmitted by the base station. The terminal can perform an uplink synchronization procedure using at least one of the TAC, common TA, or UE-specific TA of the received MAC CE.

[0143] The base station can transmit SSB or dedicated signaling to the terminal (S960). The terminal can receive the SSB or dedicated signaling transmitted by the base station. The terminal can update common TA parameters using SSB or dedicated signaling. The terminal can update satellite astronomical information using SSB or dedicated signaling. The terminal can update absolute time using SSB or dedicated signaling.

[0144] Meanwhile, when performing RACH-less handover in a non-terrestrial network, the base station may use a reference signal (RS) resource that uses the same beam (e.g., the same beam index) as the SS / PBCH block to schedule the initial PUSCH transmission. The reference signal (RS) resource using the SS / PBCH block index may have quasi-co-location characteristics for PDCCH reception.

[0145] Figure 10a is a conceptual diagram illustrating embodiments of a handover procedure.

[0146] Referring to Fig. 10a, in an EFB environment, satellites (the first satellite and the second satellite) can form cell coverage. At this time, beam coverage can be formed by at least one beam area (e.g., beam spot). A beam area can mean an area covered by a single beam. In other words, a satellite can form one or more beam areas (beam spots).

[0147] In an EFB environment, all terminals within the same beam area can request a handover procedure from the satellite at the same or similar time points. If terminals are within the same beam area, they may have the same remaining cell time. This allows the satellite to group all terminals within the same beam area together.

[0148] Figure 10b is a conceptual diagram illustrating embodiments of a handover procedure.

[0149] Referring to FIGS. 10A and 10B, in an EFB-based NTN (hereinafter, referred to as “EFB NTN”), each of the first satellite and the second satellite can move over time (e.g., from the first time to the second time) and support EFB. The second time may be after the first time. The handover procedure can be classified into an intra-SAT (satellite) handover procedure and an inter-SAT handover procedure. Each of the intra-SAT handover procedure and the inter-SAT handover procedure can be a normal handover procedure or a CHO (conditional handover) procedure. In the intra-SAT handover procedure, terminal(s) can perform a handover procedure for cells of the same satellite. That is, the intra-SAT handover procedure can be performed through beam switching on the same satellite. For example, in the intra-SAT handover procedure, all terminals connected to the first cell of the first satellite can be handed over to the second cell of the first satellite. In this case, all UEs can be handed over to the second cell at the same or similar time. EFB can be supported through beam steering within the same satellite.

[0150] In an inter-SAT handover procedure, terminal(s) may perform a handover procedure for satellites. In an inter-SAT handover procedure, all UEs connected to a first satellite (e.g., a specific cell of the first satellite) may be handed over to a second satellite (e.g., a specific cell of the second satellite). In this case, all terminals may be handed over to the second satellite at the same or similar times. The handover procedure performed during the period from the first time to the second time may be an inter-SAT handover procedure. EFB may be supported through a new cell of a new satellite (e.g., the second satellite).

[0151] Due to the high altitude of the NTN, RSRP-based handover procedures may not be efficient. Therefore, a handover procedure suitable for NTN is needed. In an EFB NTN, cell coverage on the ground can be maintained even when a satellite moves. That is, the satellite can support a fixed cell coverage. Intra-SAT and / or inter-SAT handover procedures can be performed simultaneously for terminals within the same cell (e.g., all terminals or some terminals). An efficient handover procedure that takes into account the characteristics of the EFB NTN described above is needed.

[0152] In an EFB environment, even if satellites (first satellite, second satellite) move, the existing beam coverage (860) on the ground can be maintained. The beam coverage may be referred to as a cell area on the ground. In an EFB environment, satellites (first satellite, second satellite) can maintain a fixed cell area through beam steering or beam switching. As the existing satellite moves, the cell area can be serviced by a new satellite. When the cell area starts to be serviced by a new satellite, the elevation angle between the cell area and the new satellite may be the smallest. The elevation angle may increase as the satellite moves. After the elevation angle increases, the elevation angle may decrease again as the satellite moves further. At this time, the distance between the satellite and the cell may decrease or increase depending on the change in the elevation angle.

[0153] Figure 11 is a conceptual diagram illustrating examples of beam footprints in an EFB environment.

[0154] Referring to FIG. 11, a satellite (or UAS (Unmanned Aerial Vehicle) platform) (1110) can support multi-beams. The satellite can form cell coverage through multi-beams. The satellite can form a beam footprint included in the cell coverage formed by the satellite. At this time, the radius of the cell coverage formed by the satellite can be several tens of kilometers. Meanwhile, the satellite's moving speed can be 7.56 km / s.

[0155] Figure 12 is a conceptual diagram illustrating embodiments of EMB (earth moving beam).

[0156] Referring to Fig. 12, a satellite beam may have an EMB (earth moving beam) characteristic. When a satellite (1210, 1220) moves in an EMB environment, the ground cell area (1260, 1270) may change according to the movement of the satellite. Therefore, a satellite servicing a terminal in a specific area may continuously change. At this time, a terminal included in the beam coverage of a specific satellite may have a data service time by a specific satellite depending on the location of the beam coverage. In other words, the remaining cell time of the terminal may vary depending on the location of the terminal. The remaining cell time may refer to the remaining time that the terminal is serviced in the corresponding cell depending on the location of the terminal within the beam coverage. In other words, the remaining cell time may be the time during which communication services can be provided to the terminal in the cell in which the terminal is located. When the remaining cell service time expires, the terminal may need to perform a procedure to (re)select another cell.

[0157] Figure 13a is a conceptual diagram illustrating embodiments for explaining handover of a non-terrestrial network.

[0158] Referring to Figure 13a, the intra-satellite handover procedure may involve changes in both the service link and / or the feeder link.

[0159] Figure 13b is a conceptual diagram illustrating embodiments for explaining handover of a non-terrestrial network.

[0160] Referring to Figure 13b, the inter-SAT handover procedure may not change the service link, but may change the feeder link.

[0161] Meanwhile, NTN satellite systems may experience EFB and EMB environments due to changes in ground beam footprints caused by satellite movement. Applying the same grouping method to both scenarios may be inefficient. It may be difficult to achieve the handover signaling reduction effect through grouping. Therefore, in non-terrestrial network handover procedures, the satellite can transmit the changed TA to the terminal when changing base stations.

[0162] Meanwhile, TA information for a terminal in a non-terrestrial network can be configured as follows. A satellite can perform RACH-less handover in a non-terrestrial network. The satellite can configure TA information when performing a RACH-less handover procedure. When performing a RACH-less handover procedure in a non-terrestrial network environment, timing difference information may be different for each terminal. The timing difference information may include a difference value between the timing value of the source cell and the timing value of the target cell in the timing information of the source cell and the timing information of the target cell. The satellite can obtain timing information for each cell to calculate the timing difference information. Timing information in a non-terrestrial network can be expressed as in the following mathematical expression 1.

[0163]

[0164]

[0165] may mean timing information. may mean the delay between the RP (Reference point) and the satellite. may be referred to as a common TA. may mean a delay in the service link. may mean the TA value estimated by the terminal. may be referred to as UE-specific TA. UE-specific TA may refer to the round trip delay (RTD) between the UE and the satellite. In other words, may refer to a delay value between the terminal and the satellite. Meanwhile, the terminal may perform a closed-loop timing control procedure by a TA command message transmitted by the base station.

[0166] is in the terrestrial network It can perform the same role as TA information in NTN. This can be further defined. means the TA value to be applied UE-commonly, is a basic unit of time constant mainly used in the NR physical layer, which can mean (4096*480*1000)-1 second.

[0167] Timing difference information may include a common TA difference value. The timing difference information may refer to the difference between different common TA values. For example, the difference between different common TA values ​​may refer to the difference between the common TA value for the source cell and the common TA value for the target cell.

[0168] The common TA can be calculated based on the RP of each cell. When a UE changes cells through a handover procedure, the common TA value may change. Therefore, the UE can perform the handover procedure using timing difference information between the common TA of the source cell and the common TA of the target cell.

[0169] Timing difference information for a common TA can be transmitted to a terminal via a handover command message. The terminal can receive the handover command message transmitted by the base station. The handover command message can include a common TA difference value. The terminal can independently calculate a terminal-specific TA value. The terminal can obtain timing information for a target cell based on the common TA difference value and the terminal-specific TA value. In addition, the terminal can perform a RACH-less handover using the timing information for the target cell.

[0170] Meanwhile, if the RP of the source cell and the RP of the target cell are set differently, the base station can transmit a timing difference value due to the RP difference to the terminal.

[0171] The timing difference value for the common TA and the timing difference value due to the RP difference can be transmitted to the terminal using two parameters. Furthermore, the timing difference value for the common TA and the timing difference value due to the RP difference can be transmitted to the terminal using a single parameter. For example, FL_TA_diff can be defined to include the common TA difference value and the timing difference value due to the RP difference. Furthermore, the satellite can redefine and use the common TA.

[0172] Meanwhile, in a Feeder Link Switch situation, TA information can be updated as follows.

[0173] FIG. 14a is a conceptual diagram illustrating embodiments of a feeder link switch environment, and FIG. 14b is a conceptual diagram illustrating embodiments of a feeder link switch environment.

[0174] Referring to FIGS. 14A and 14B, the base station can update the TA value in a situation where a feeder link switch is performed. T1 may refer to the time when the satellite is connected to gateway 1. Additionally, T1 may refer to the time immediately before the satellite performs a handover. T2 may refer to the time when the satellite is connected to gateway 2. T2 may refer to the time immediately after the satellite performs a handover. The satellite can change gateways through the handover procedure. In other words, the satellite can perform a feeder link switch.

[0175] A feeder link switch may refer to changing the gateway or base station (gNB) associated with a satellite to another gateway or base station. In other words, a feeder link switch may refer to changing the gateway or base station without changing the satellite. When a satellite performs a feeder link switch procedure, differences in service link delay and / or feeder link delay may occur. Here, the service link delay may be a common value.

[0176] The feeder link delay difference can be calculated based on the satellite's location, the gateway's location, or the base station's location. During the handover procedure, the satellite can transmit information about the feeder link delay difference to all terminals within the cell it supports. A parameter representing the feeder link delay difference can be defined as FL_TA_diff. The satellite can generate a handover command message containing FL_TA_diff and transmit the handover command message to the terminal.

[0177] At this time, the FL_TA_diff value can have a range of [-X, +X]. X can be a parameter set in advance through an RRC message. At this time, the FL_TA_diff value can be defined by a table having a total of 2^N values. The FL_TA_diff value can be transmitted to the terminal by utilizing the index of the table having 2^N values.

[0178] The RP (Reference Point) of the feeder link formed through gateway 1 may be located at gateway 1. The RP (Reference Point) may mean any location (or time point) existing on the feeder link between the gateway (or ground base station) and the satellite. The RP (Reference Point) of the feeder link formed through gateway 2 may be located at gateway 2. The common TA value may mean a value between the base station and the RP. In this case, the FL_TA_diff value may be equal to the difference in the common TA values ​​(the difference between the common TA value for gateway 1 and the common TA value for gateway 2).

[0179] A Reference Point (RP) may be located in at least one of a base station, satellite, feeder link, or service link for uplink synchronization. The location of the RP may not be limited. The RP location may not be transmitted to the UE. Therefore, the common TA may not be estimated by the UE, and may be calculated by the network.

[0180] When a feeder link formed through a gateway establishes a different RP, the FL_TA_diff value may differ from the common TA value. In this case, the FL_TA_diff value may include a timing difference value resulting from the difference in the common TA and the position difference of the RPs.

[0181] The satellite can generate an RRC message including a difference value of common TA and a timing difference value due to RP position difference instead of a single parameter FL_TA_diff, and transmit the RRC message to the terminal.

[0182] The present disclosure can set up timing groups to improve the performance of handover procedures in non-terrestrial network environments.

[0183] Figure 15 is a conceptual diagram illustrating embodiments of timing group settings.

[0184] Referring to Figure 15, when an inter-SAT handover is requested from a terminal in an EFB environment, the feeder link and service link can be changed. When performing a handover procedure in an EFB environment, the satellite can change the transmission path immediately before and after the handover. When performing a handover procedure, the satellite can perform the handover procedure using four linearly configured timing groups (TG).

[0185] A timing group may refer to a group of terminals with identical or similar timing information. A timing group may be composed of terminals. A timing group may include terminals whose timing values ​​differ by no more than △T from the reference value.

[0186] The reference value may refer to a timing value for the center position of the set distance value defined by the base station associated with the satellite. For example, the reference value of timing group 1 may refer to Tref1. Tref1 may refer to a timing value corresponding to the center position of timing group 1. Tref1 may be expressed as follows: Tref1=△T. Tref2 may refer to a reference value of timing group 2. Tref2 may refer to a timing value corresponding to the center position of timing group 2. Tref2 may be expressed as follows: Tref2= Tref1+2△T. In addition, Tref3 may refer to a reference value of timing group 3. Tref3 may refer to a timing value corresponding to the center position of timing group 3. Tref3 may be expressed as follows: Tref3=Tref2+2△T. Tref4 may refer to a reference value of timing group 4. Tref4 may refer to a timing value corresponding to the center position of timing group 4. Tref4 may be expressed as follows. Tref4=Tref3+2△T. △T may refer to a parameter preset by an RRC message. △T may refer to the first TA range. The base station may set the first TA range.

[0187] Accordingly, the base station can configure a timing group using timing group configuration information. The timing group configuration information can include a timing group index of the terminal. In other words, the base station can transmit the configured timing group index to each terminal. The base station can transmit the timing group index configured by the base station to each terminal via RRC signaling. The timing group index can include an identification number of the group configured for the terminal. The terminal can receive the timing group index transmitted by the base station. The terminal can identify the timing group of the terminal through the timing group index.

[0188] A timing group may be composed of terminals located within a certain distance from a location having a reference value. The timing group may be set by considering △T. In addition, the timing group may be set by considering a certain distance from a location having a reference value. In other words, the timing group may be set by using at least one of △T or a certain distance from a location having a reference value. The center position of the timing group may be obtained using the location information of the terminals. In this case, the terminal may obtain its location information through a global navigation satellite system (GNSS).

[0189] In cases where people are densely packed in a confined space, the satellite can establish a timing group based on the timing value of the central location of the area (the confined space). The satellite can assign the same timing group to terminals within a certain distance from the central location of the area. The satellite can assign the same timing group to terminals that have a timing value that differs from the central location of the area by a predefined value.

[0190] In other words, the base station can set a timing group for terminals whose timing value difference (e.g., reference value - terminal timing value) is within △T. The reference value can mean a timing value for the center position of the region or a value set by the base station (Tref1, Tref2, Tref3, Tref4). The reference value is a value set by the base station and can mean a constant value.

[0191] When performing a handover procedure, terminals can receive changed timing information from the base station. The base station can select a method for transmitting the changed timing information to the terminals.

[0192] The terminals within each timing group can have the same common TA. When performing a handover procedure, the common TA value can be changed. Therefore, the base station can transmit the difference in the common TA value to the terminals within the timing group. The common TA value can be included in a handover command message. The base station can transmit the handover command message to the terminals within the group. The base station can transmit the handover command message to the terminals within the timing group through group-based signaling. In other words, the base station can transmit the handover command message to the terminals within the timing group through common signaling such as groupcast.

[0193] The common TA can be calculated based on the RP of each cell. Therefore, when a handover procedure that changes cells is performed, the common TA can be changed. Accordingly, when performing a handover procedure, the terminals can receive information about the difference between the common TA of the source cell and the common value of the target cell. The base station can transmit the common TA difference information to the terminals via a handover command message. The terminal can obtain timing information about the target cell through the common TA difference value transmitted from the base station and the terminal-specific TA value calculated by the terminal. In addition, the terminal can perform a RACH-less handover using the acquired timing information about the target cell.

[0194] When the RP changes, the base station can generate a handover command message including additional timing information and transmit the handover command message to the terminals.

[0195] Meanwhile, the base station can set a center point of the timing group. The center point of the timing group can refer to a geographically central location. Additionally, the center point of the timing group can refer to a median value of the timing values ​​of each terminal within the timing group. The base station can transmit a timing difference value based on the center point (e.g., a reference value) to the terminals. The base station can generate a handover command message including the timing difference value based on the center point (e.g., a reference value) and transmit the handover command message to the terminals. For example, the base station can transmit to the terminal the timing difference value for the path from the center point (e.g., the reference value) to the base station via satellite 1 and the timing difference value for the path from the center point (e.g., the reference value) to the base station via satellite 2.

[0196] Meanwhile, in a non-terrestrial network environment, the base station can perform an open loop timing control procedure using a common TA value and a terminal-specific TA value. In a terrestrial network environment, the base station can perform a closed loop timing control procedure. The reason for introducing an open loop timing control procedure in a non-terrestrial network environment is that the open loop timing control procedure is utilized. , It may be used to perform timing control procedures in a non-terrestrial network environment by utilizing parameters. At this time, the utilized , Parameters may not have their length changed.

[0197] However, since the handover command message has no restrictions on changing the length of parameters, the base station can transmit a timing difference value based on the center point of each timing group to the terminals.

[0198] In densely populated areas, terminals may be clustered in a small area. Therefore, the base station can transmit timing values ​​based on the center point of the timing group to the terminals within the timing group. The terminals can then perform a RACH-less handover procedure using the timing values ​​based on the center point of the timing group transmitted by the base station.

[0199] For example, if the timing group is set based on half the CP (cyclic prefix) length for the signal, and the Sub-carrier Spacing (SCS) is 15 kHz, the CP length is 4.7 uesc, so the base station can set terminals within 705 meters to the same timing group considering the propagation speed of 2.35 usec, which is half the CP length. In other words, the base station can set terminals within a radius of approximately 705 meters to the same timing group. Terminals within 705 meters can perform initial access with the same timing value.

[0200] The base station can transmit to the terminal a timing difference value based on the center point of the timing group and information about the center point of the timing group. The terminal can calculate an additional timing adjustment value using its location information and satellite astronomical information. The terminal can perform a RACH-less handover using the timing adjustment value. If the terminal cannot receive a GNSS signal, it can perform a RACH-less handover using the timing adjustment value.

[0201] Figure 16 is a conceptual diagram illustrating embodiments of a handover procedure in an EMB environment.

[0202] Referring to Fig. 16, the remaining time of terminals included in a beam spot in an EMB environment may be different. The remaining time may refer to the time remaining until the handover request time of the terminals belonging to the beam spot. The remaining time may vary depending on the location of the terminals belonging to the beam spot. For example, a beam spot (1611) may include multiple terminals. The multiple terminals may refer to a primary terminal (1621), a square terminal (1622), and a triangular terminal (1623). At this time, the primary terminal (1621) can receive service for the longest time compared to other terminals (the square terminal (1622), the triangular terminal (1623)) considering the satellite's traveling direction. In other words, the primary terminal (1621) can perform the handover procedure last compared to other terminals (the square terminal (1622), the triangular terminal (1623)). Accordingly, the original terminals (1621) can have a greater remaining time than other terminals (square terminals (1622), triangle terminals (1623)). Terminals belonging to the beam spot (1611) can perform the handover procedure in the order of the smallest remaining time value.

[0203] Meanwhile, terminals may have different target satellites for the handover procedure even if they have the same remaining time depending on their location. For example, the original terminal (1621) and the square terminal (1622) may be included in different beam spots even if they have the same remaining time. Therefore, the handover procedure for the original terminal (1621) and the square terminal (1622) may be performed by different target satellites.

[0204] Therefore, the base station can establish a group so that terminals within the group can perform a handover procedure through common signaling. The base station can group terminals using the remaining time value and additional information. Group configuration can be established at the base station. The established group information can be transmitted to the terminals as an index for the group. At this time, the terminal can select a target satellite when performing the handover procedure. If the terminal determines the target satellite, the base station can establish a group using the ID of the target satellite. The base station can establish a group using the terminal's location information and the satellite's astronomical information.

[0205] Figure 17 is a conceptual diagram illustrating embodiments of a handover procedure in an EMB environment.

[0206] Referring to Figure 17, in an EMB environment, handovers can occur sequentially among terminals based on the satellite's movement. In other words, the base station can perform the handover procedure by considering the timing group index. The satellite's beam spot can be a timing group with the same common TA. The base station can predetermine the satellite's movement (speed, direction, altitude) in the non-terrestrial network. The base station can utilize the TA information from the previous area to predict or calculate the TA information for the next area.

[0207] Figure 18 is a conceptual diagram illustrating embodiments of a handover procedure in an EMB environment.

[0208] Referring to Figure 18, handovers in an EMF environment can occur in batches at the cell or beam level. However, handovers in an EMB environment can occur continuously. Figure 18 may illustrate a method for updating timing information in a handover procedure that occurs continuously in an EMB environment.

[0209] In an EMB environment, a base station can set timing groups for terminals (S1810). Terminals may refer to terminals in the same beam spot. The base station can set terminals into timing groups using the remaining time. The remaining time may be set as [reference value, reference value + △T]. The base station can set terminals having the same target cell into timing groups. For example, if the reference value of timing group 1 is 0, the reference value of timing group 2 may be △T, and the reference value of timing group 3 may be 2△T. Therefore, the remaining time of timing group 1 may be [0, △T]. The remaining time of timing group 2 may be [△T, 2△T]. The remaining time of timing group 3 may be [2△T, 3△T]. In other words, timing group 2 may be composed of terminals whose remaining times are [△T, 2△T].

[0210] The base station can assign numbers to each timing group (S1820). The base station can assign numbers in order of the remaining time of the timing group.

[0211] A base station can transmit TA information to all terminals within a timing group at a specific point in time (S1830). The specific point in time can refer to any value set by the base station. The specific point in time can be referred to as t. In this case, the TA information can refer to TA information for a specific point in time.

[0212] Terminals can use the same TA information during △T (S1840).

[0213] The base station can transmit TA information to all terminals within the next timing group (S1850). The base station can transmit TA information to all terminals within the next timing group after △T has elapsed. At this time, the TA information may refer to TA information for a specific point in time plus △T.

[0214] The base station can determine whether the timing group of the terminals transmitting TA information is the final timing group (S1860). If the timing group for the terminal is not the final timing group, the base station and the terminal can re-perform steps S1840 and S1850. If the timing group is the final timing group, the base station can terminate the procedure.

[0215] The operations of the method according to 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 any type of recording device that stores information readable by a computer system. Furthermore, a computer-readable recording medium can be distributed across network-connected computer systems, allowing the computer-readable program or code to be stored and executed in a distributed manner.

[0216] Additionally, the computer-readable recording medium may include hardware devices specifically configured to store and execute program instructions, such as ROM, RAM, flash memory, etc. The program instructions may include not only machine language codes produced by a compiler, but also high-level language codes that can be executed by a computer using an interpreter, etc.

[0217] While some aspects of the present disclosure have been described in the context of a device, they may also represent a description of 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 as 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 or more of the most significant method steps may be performed by such a device.

[0218] 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 in the present disclosure. The field-programmable gate array may operate in conjunction with a microprocessor to perform one of the methods described in the present disclosure. In general, the methods are preferably performed by some hardware device.

[0219] Although the present disclosure has been described with reference to preferred embodiments thereof, it will be understood by those skilled in the art that various modifications and changes may be made to the present disclosure without departing from the spirit and scope of the present disclosure as set forth in the claims below.

Claims

1. In the UE (User Equipment) method, A step of receiving timing group setting information for a timing group including the UE from the first satellite based on a beam spot supported by the first satellite; A step of receiving a handover command message including timing information of the UE from the first satellite according to a timing group index included in the timing group setting information; A step of obtaining TA (Timing Advance) information using the above timing information; and Including a step of transmitting a handover completion message using the above TA information, UE's method.

2. In claim 1, The above timing group setting information is: If the difference value between the timing value of the UE and the timing value for the center position of the set distance value defined by the base station associated with the first satellite falls within the first TA range set by the base station, including the timing group index for identifying the timing group including UEs within the first TA range, UE's method.

3. In claim 1, The above timing group setting information is: Including the timing group index for identifying the timing group including UEs within the distance range set by the base station from the center position of the beam area, UE's method.

4. In claim 1, The above timing group setting information is: When the cell remaining time, which is the time during which communication service for the beam area is provided to the UE, falls within the time range set by the first satellite, the timing group index for identifying the timing group including UEs having cell remaining time within the time range is included. UE's method.

5. In claim 1, The step of obtaining TA information using the above timing information is: A step of obtaining TA information using a timing difference value corresponding to a difference between a first path including a path between the first satellite and a path between the first satellite and a base station at a central location of the timing group and a second path including a path between the second satellite and a path between the second satellite and a base station at a central location of the timing group, UE's method.

6. In claim 1, The step of obtaining TA information using the above timing information is: a step in which the UE determines a UE-specific TA value on its own; and A step of obtaining the TA information by updating the TA value for the UE using at least one of the UE specific TA value, a common TA value equally applied to all UEs of the source cell included in the timing information, a common TA value equally applied to all UEs of the target cell, or a timing difference value due to a difference in RP (Reference Point) between the source cell and the target cell. UE's method.

7. In claim 1, The step of obtaining TA information using the above timing information is: A step of receiving at least one of the location information of the UE, the location information of the first satellite, or satellite astronomical information from the first satellite; and A step of calculating a timing adjustment value for the UE using at least one of the location information of the UE, the location information of the first satellite, and the satellite astronomical information; Comprising a step of obtaining the TA information using the timing adjustment value and the timing information, UE's method.

8. In the method of the base station, A step for setting timing group setting information for a timing group including a UE (User Equipment) based on a beam spot supported by the first satellite; A step of transmitting a handover command message including timing information for the timing group to which the UE belongs, to the UE, according to a timing group index included in the timing group setting information; and A step of receiving a handover completion message from the UE that performed the handover procedure through the timing information for the timing group to which the UE belongs. Method of base station.

9. In claim 8, The steps for setting the above timing group setting information are: A step of setting the UE to the timing group when the difference value between the timing value of the UE and the timing value for the center position of the set distance value defined by the base station communicating through the first satellite is equal to or less than the second TA value defined by the base station for the timing group, Method of base station.

10. In claim 8, The steps for setting the above timing group setting information are: Including a step of setting the UE to the timing group when the cell remaining time, which is the time during which communication service for the beam area is provided to the UE, falls within the time range set by the first satellite. Method of base station.

11. In claim 8, The above timing information is, At least one of a common TA value applied equally to all UEs of the source cell included in the timing information, a common TA value applied equally to all UEs of the target cell, or a timing difference value due to a difference in RP (Reference Point) between the source cell and the target cell is included. Method of base station.

12. In UE(user equipment), Contains at least one processor, At least one processor of the UE, Receive timing group setting information for a timing group including the UE from the first satellite based on the beam spot supported by the first satellite, Receive a handover command message including timing information of the UE from the first satellite according to the timing group index included in the timing group setting information; Using the above timing information, TA (Timing Advance) information is obtained, and Causing a handover completion message to be transmitted using the above TA information, UE.

13. In claim 12, The above timing group setting information is: If the difference value between the timing value of the UE and the timing value for the center position of the set distance value defined by the base station associated with the first satellite falls within the first TA range set by the base station, causing the timing group index to be included for identifying the timing group including UEs within the first TA range. UE.

14. In claim 12, The above timing group setting information is: If the UE falls within a distance range set by the base station from the center position of the beam area, causing the timing group index to be included for identifying the timing group including the UEs within the distance range. UE.

15. In claim 12, The above timing group setting information is: If the cell remaining time, which is the time during which communication service for the beam area is provided to the UE, falls within the time range set by the first satellite, causing the timing group index to be included for identifying the timing group including UEs having cell remaining time within the time range, UE.

16. In claim 12, In case of obtaining TA information using the above timing information, the at least one processor causes the UE to, Causing to obtain TA information by using a timing difference value corresponding to the difference between a first path including a path between the first satellite and a path between the first satellite and a base station at a central location of the timing group and a second path including a path between the second satellite and a base station at a central location of the timing group. UE.

17. In claim 12, In case of obtaining TA information using the above timing information, the at least one processor causes the UE to, The above UE determines the UE specific TA value by itself, and Causing to include a step of obtaining the TA information by updating the TA value for the UE using at least one of the UE specific TA value, a common TA value equally applied to all UEs of the source cell included in the timing information, a common TA value equally applied to all UEs of the target cell, or a timing difference value due to a difference in RP (Reference Point) between the source cell and the target cell. UE.

18. In claim 12, In case of obtaining TA information using the above timing information, the at least one processor causes the UE to, Receive at least one of the location information of the UE, the location information of the first satellite, or satellite astronomical information from the first satellite, Calculate a timing adjustment value for the UE by using at least one of the position information of the UE, the position information of the first satellite, and the satellite astronomical information, Causing the TA information to be acquired by using the timing adjustment value and the timing information. UE.

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