Method and apparatus for group handover configuration in non-terrestrial networks

Abstract

A method and apparatus for group handover configuration in a non-terrestrial network are disclosed. The method for a user equipment (UE) may comprise the steps of: receiving, from a satellite, group configuration information on a group including the UE based on a beam point supported by the satellite; receiving, from the satellite, a group indicator indicating the group; measuring channel state information (CSI) on the group; reporting a message including the CSI to a satellite; and receiving, from the satellite, a handover command message for a handover determined based on the measurement result of the CSI.

Description

Technical Field

[0001] The present invention relates to group handover techniques in non-terrestrial networks, and more particularly, to techniques for configuring groups for group handover. Background Art

[0002] Communication networks (e.g., 5G communication networks, 6G communication networks, etc.) are being developed to provide enhanced communication services compared to existing communication networks (e.g., long term evolution (LTE), LTE-Advanced (LTE-A), etc.). A 5G communication network (e.g., a New Radio (NR) communication network) can support not only bands below 6 GHz but also bands above 6 GHz. That is, a 5G communication network can support frequency range FR1 bands and / or FR2 bands. Compared with an LTE communication network, a 5G communication network can support a variety of communication services and scenarios. For example, the usage scenarios of a 5G communication network can include enhanced Mobile BroadBand (eMBB), Ultra Reliable Low Latency Communication (URLLC), massive Machine Type Communication (mMTC), etc.

[0003] Compared with a 5G communication network, a 6G communication network can support a variety of communication services and scenarios. A 6G communication network can meet the requirements of super performance, super bandwidth, super space, super precision, super intelligence, and / or super reliability. A 6G communication network can support various wide frequency bands and can be applied to various usage scenarios (e.g., terrestrial communication, non-terrestrial communication, sidelink communication, etc.).

[0004] Communication networks (e.g., 5G communication networks, 6G communication networks, etc.) can provide communication services to terminals located on the ground. Recently, the demand for communication services not only on the ground but also for non-terrestrial aircraft, drones, and satellites has been increasing. For this purpose, techniques for non-terrestrial networks (NTN) have been discussed. A non-terrestrial network can be implemented based on 5G communication technology, 6G communication technology, etc. For example, in a non-terrestrial network, communication between a satellite and a terrestrial communication node or a non-terrestrial communication node (e.g., an aircraft, a drone, etc.) can be performed based on 5G communication technology, 6G communication technology, etc. In an NTN, a satellite can perform the functions of a base station in a communication network (e.g., a 5G communication network, a 6G communication network, etc.).

[0005] On the other hand, in a terrestrial network (TN), handovers may occur based on the individual movement of terminals. Accordingly, handover request messages may be sent to satellites in a distributed manner according to the movement of the corresponding terminals. Therefore, when the handover process is executed simultaneously by multiple terminals, the handover process may not be successfully executed. When the base station processes multiple handovers simultaneously, processes such as signal strength measurement and reporting at the terminal, handover requests and responses, and handover commands may be executed simultaneously, resulting in an increase in signaling overhead.

[0006] On the other hand, in a non-terrestrial network (NTN), handovers may occur due to the movement of satellites. In this case, due to the movement of satellites, multiple terminals may experience handovers simultaneously. Additionally, due to the high speed of satellites, frequent handovers may occur. Therefore, in a non-terrestrial network, the satellite and / or the base station may experience a high load when processing simultaneous handovers. Accordingly, the present invention proposes a method for handling handovers based on groups in order to reduce the load that occurs during the handling of a large number of handovers in an NTN environment. Summary of the Invention

[0007] Technical Problem

[0008] The present invention is directed to providing a method and apparatus for group handover configuration in a non-terrestrial network.

[0009] Technical Solution

[0010] A method for a user equipment (UE) for achieving the above object according to a first exemplary embodiment of the present invention may include: receiving, from a satellite, group configuration information for a group including the UE based on a beam area supported by the satellite; receiving a group indicator indicating the group from the satellite; measuring channel state information (CSI) of the group; reporting a message including the CSI to the satellite; and receiving a handover command message for a handover determined based on the result of measuring the CSI from the satellite.

[0011] The group configuration information may include at least one group identifier (ID) based on the beam area.

[0012] When the cell remaining time falls within a time range configured by the satellite, the group configuration information may include a group ID for identifying a group including the UE having the cell remaining time, where the cell remaining time is the time for which the UE is in a state served by the beam area.

[0013] The method may further include: determining a beam area that occupies the largest portion of a tracking area in a beam area supported by the satellite as a beam area related to the tracking area.

[0014] The method may further include: determining a beam region for supporting a UE based on beam region determination information, where the beam region determination information includes at least one of location information of the UE, ephemeris information of the satellite, or information of a target base station.

[0015] The method may further include: receiving from the satellite at least one of an indicator indicating to perform a CSI measurement process and a CSI reporting process or an indicator indicating not to perform a CSI measurement process and a CSI reporting process.

[0016] Receiving a handover command message from the satellite may include: receiving from the satellite information that the satellite generally sends to a group through a unicast, multicast, or broadcast scheme.

[0017] A method of a satellite for achieving the above object according to a second exemplary embodiment of the present invention may include: configuring a group for a user equipment (UE) served by the satellite based on a beam region supported by the satellite; sending a group indicator for the group to the UE; selecting at least one UE from the UE to perform a channel state information (CSI) measurement process and a CSI reporting process; receiving a message including the CSI of the group from at least one UE; sending a handover request message for a handover determined based on the CSI to a target satellite; receiving a handover request confirmation message from the target satellite, where the handover request confirmation message indicates that the handover request according to the handover request message is approved; and in response to the handover request of the satellite being approved by the target satellite, sending a handover command message to the UE belonging to the group.

[0018] Configuring a group for a UE served by the satellite may include: configuring a group for the UE based on at least one of a beam region, a cell remaining time, or beam region determination information, where the cell remaining time is the time when the UE is in a state served by the beam region, and where the beam region determination information may include at least one of location information of the UE, ephemeris information of the satellite, or information of a target satellite.

[0019] Selecting at least one UE to perform a CSI measurement process and a CSI reporting process may include: selecting, from the UE, a UE whose cell remaining time falls within a time range configured by the satellite as at least one UE to perform a CSI measurement process and a CSI reporting process, where the cell remaining time is the time when the UE is in a state served by the beam region.

[0020] Sending a handover command message to the UE belonging to the group may include: sending, through a unicast, multicast, or broadcast scheme, information that is generally sent to a group to the UE.

[0021] A user equipment (UE) for achieving the above object according to a third exemplary embodiment of the present invention may include: at least one processor, wherein the at least one processor may cause the UE to perform: receiving, from a satellite, group configuration information for a group including the UE based on a satellite-supported beam region; receiving, from the satellite, a group indicator indicating the group; measuring channel state information (CSI) of the group; reporting a message including the CSI to the satellite; and receiving, from the satellite, a handover command message for a handover determined based on the result of measuring the CSI.

[0022] The group configuration information may include at least one group identifier (ID) based on the beam region.

[0023] When the cell remaining time falls within a time range configured by the satellite, the group configuration information may include a group ID for identifying a group including the UE having the cell remaining time, where the cell remaining time is the time when the UE is in a state served by the beam region.

[0024] The at least one processor may cause the UE to perform: determining, as a beam region related to the tracking area, a beam region that occupies the largest part of the tracking area in the satellite-supported beam region.

[0025] The at least one processor may cause the UE to perform: determining a beam region supporting the UE based on beam region determination information including at least one of the UE's location information, the satellite's ephemeris information, or the target base station's information.

[0026] The at least one processor may cause the UE to perform: receiving, from the satellite, at least one of an indicator indicating to perform the CSI measurement process and the CSI reporting process or an indicator indicating not to perform the CSI measurement process and the CSI reporting process.

[0027] When receiving the handover command message from the satellite, the at least one processor may cause the UE to perform: receiving, from the satellite, information that the satellite generally sends to the group through a unicast, multicast, or broadcast scheme.

[0028] Advantageous Effects

[0029] According to the present invention, in a non-terrestrial network, a satellite may configure terminals into a group. Some terminals within the group may send CSI to a base station based on a group indicator. According to the above operations, in a non-terrestrial network, group handover may reduce the load generated during the handover process, and group handover may also reduce the load related to the CSI measurement process and reporting process of terminals configured into a group. Description of the Drawings

[0030] Figure 1a is a conceptual diagram showing a first exemplary embodiment of a non-terrestrial network.

[0031] Figure 1b It is a conceptual diagram showing a second exemplary embodiment of a non-terrestrial network.

[0032] Figure 2a It is a conceptual diagram showing a third exemplary embodiment of a non-terrestrial network.

[0033] Figure 2b It is a conceptual diagram showing a fourth exemplary embodiment of a non-terrestrial network.

[0034] Figure 2c It is a conceptual diagram showing a fifth exemplary embodiment of a non-terrestrial network.

[0035] Figure 3 It is a block diagram showing a first exemplary embodiment of a communication node constituting a non-terrestrial network.

[0036] Figure 4 It is a block diagram showing a first exemplary embodiment of a communication node performing communication.

[0037] Figure 5a It is a block diagram showing a first exemplary embodiment of a transmission path.

[0038] Figure 5b It is a block diagram showing a first exemplary embodiment of a reception path.

[0039] Figure 6a It is a conceptual diagram showing a first exemplary embodiment of a protocol stack of a user plane in a non-terrestrial network based on a transparent payload.

[0040] Figure 6b It is a conceptual diagram showing a first exemplary embodiment of a protocol stack of a control plane in a non-terrestrial network based on a transparent payload.

[0041] Figure 7a It is a conceptual diagram showing a first exemplary embodiment of a protocol stack of a user plane in a non-terrestrial network based on a regenerated payload.

[0042] Figure 7b It is a conceptual diagram showing a first exemplary embodiment of a protocol stack of a control plane in a non-terrestrial network based on a regenerated payload.

[0043] Figure 8 It is a conceptual diagram for describing an EFB.

[0044] Figure 9 It is a conceptual diagram for describing an EMB.

[0045] Figure 10a It is a conceptual diagram showing a first exemplary embodiment of a handover process.

[0046] Figure 10b It is a conceptual diagram showing a second exemplary embodiment of the handover process.

[0047] Figure 11 It is a conceptual diagram showing a third exemplary embodiment of the handover process.

[0048] Figure 12 It is a sequence diagram showing a first exemplary embodiment of the handover process.

[0049] Figure 13 It is a sequence diagram showing a second exemplary embodiment of the handover process.

[0050] Figure 14 It is a conceptual diagram showing a first exemplary embodiment of the tracking area.

[0051] Figure 15 It is a conceptual diagram showing a first exemplary embodiment of the beam area determination method. Detailed Description

[0052] Although the present invention is capable of various modifications and alternative forms, specific embodiments thereof are shown by way of example in the drawings and will be described in detail herein. However, it should be understood that there is no intention to limit the present invention to the specific forms disclosed, but on the contrary, the present invention covers all modifications, equivalents, and alternative forms falling within the spirit and scope of the present invention. Throughout the description of the drawings, like reference numerals refer to like elements.

[0053] It will be understood that although the terms first, second, etc. may be used herein to describe various elements, these elements should not be limited by these terms. These terms are only used to distinguish one element from another. For example, without departing from the scope of the present invention, a first element may be referred to as a second element, and similarly, a second element may be referred to as a first element. As used herein, the term "and / or" includes any combination and all combinations of one or more of the associated listed items.

[0054] In the present invention, "at least one of A and B" may mean "at least one of A or B" or "at least one of a combination of one or more of A and B". Further, in the exemplary embodiments of the present invention, "one or more of A and B" may mean "one or more of A or B" or "one or more of a combination of one or more of A and B".

[0055] In the present invention, "(re)transmission" may refer to "transmission", "retransmission", or "transmission and retransmission", "(re)configuration" may refer to "configuration", "reconfiguration", or "configuration and reconfiguration", "(re)connection" may refer to "connection", "reconnection", or "connection and reconnection", and "(re)access" may mean "access", "reaccess", or "access and reaccess".

[0056] It will be understood that when an element is referred to as being "connected" or "coupled" to another element, it can be directly connected or coupled to the other element, or intervening elements may be present. In contrast, when an element is referred to as being "directly connected" or "directly coupled" to another element, no intervening elements are present.

[0057] The terms used herein are for the purpose of describing particular embodiments only and are not intended to limit the present invention. As used herein, the singular forms are also intended to include the plural forms unless the context clearly indicates otherwise. It will be further understood that when the terms "comprises" and / or "comprising" are used herein, they specify the presence of the stated features, numbers, steps, operations, elements, components, or combinations thereof, but do not preclude the presence or addition of one or more other features, numbers, steps, operations, elements, components, and / or combinations thereof.

[0058] Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. It will be further understood that terms (e.g., terms defined in commonly used dictionaries) should be interpreted as having a meaning consistent with their meaning in the context of the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.

[0059] Hereinafter, exemplary embodiments of the present invention will be described in more detail with reference to the accompanying drawings. To facilitate an overall understanding in describing the present invention, the same components in the drawings are denoted by the same reference numerals, and repeated descriptions thereof will be omitted. In addition to the exemplary embodiments explicitly described in the present invention, operations can also be performed according to combinations of exemplary embodiments, extensions of exemplary embodiments, and / or modifications of exemplary embodiments. The execution of some operations may be omitted, and the execution order of operations may be changed.

[0060] Even when describing a method (e.g., transmission or reception of a signal) performed at a first communication node in a communication node, the corresponding second communication node may perform a method corresponding to the method performed at the first communication node (e.g., reception or transmission of a signal). That is, when describing the operation of a user equipment (UE), the base station corresponding to the UE may perform an operation corresponding to the operation of the UE. Conversely, when describing the operation of a base station, the UE corresponding to the base station may perform an operation corresponding to the operation of the base station. In a non-terrestrial network (NTN) (e.g., payload-based NTN), the operation of a base station may refer to the operation of a satellite, and the operation of a satellite may refer to the operation of a base station.

[0061] The base station may refer to Node B, evolved Node B (eNodeB), next-generation node B (gNodeB), gNB, device, apparatus, node, communication node, base transceiver station (BTS), radio remote head (RRH), transmission reception point (TRP), radio unit (RU), roadside unit (RSU), radio transceiver, access point, access node, etc. The UE may refer to a terminal, device, apparatus, node, communication node, end node, access terminal, mobile terminal, station, subscriber station, mobile station, portable subscriber station, on-board unit (OBU), etc.

[0062] In the present invention, the signaling may be at least one of higher layer signaling, medium access control (MAC) signaling, or physical (PHY) signaling. Messages for higher layer signaling may be referred to as "higher layer messages" or "higher layer signaling messages". Messages for MAC signaling may be referred to as "MAC messages" or "MAC signaling messages". Messages for PHY signaling may be referred to as "PHY messages" or "PHY signaling messages". Higher layer signaling may refer to the sending and receiving operations of system information (e.g., master information block (MIB), system information block (SIB)) and / or RRC messages. MAC signaling may refer to the sending and receiving operations of MAC control elements (CEs). PHY signaling may refer to the sending and receiving operations of control information (e.g., downlink control information (DCI), uplink control information (UCI), and sidelink control information (SCI)).

[0063] In the present invention, "configuration operation (e.g., sending operation)" may mean "signaling the configuration information of the operation (e.g., information element or parameter) and / or the information indicating the execution of the operation". "Configuration information element (e.g., parameter)" may mean "signaling the corresponding information element". In the present invention, "signal and / or channel" may mean a signal, a channel, or "signal and channel", and "signal" may be used to mean "signal and / or channel".

[0064] The communication system may include at least one of a terrestrial network, a non-terrestrial network, a 4G communication network (e.g., Long Term Evolution (LTE) communication network), a 5G communication network (e.g., New Radio (NR) communication network), or a 6G communication network. Each of the 4G communication network, 5G communication network, and 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 of communication technologies such as LTE communication technology, 5G communication technology, or 6G communication technology. The non-terrestrial network may provide communication services in various frequency bands.

[0065] The communication network applying the exemplary embodiments is not limited to the content described below, and the exemplary embodiments may be applied to various communication networks (e.g., 4G communication network, 5G communication network, and / or 6G communication network). Here, the communication network may be used in the same sense as the communication system.

[0066] Figure 1aIt is a conceptual diagram showing a first exemplary embodiment of a non-terrestrial network.

[0067] As Figure 1a shown, a non-terrestrial network (NTN) 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 correspond to a remote radio unit (RRU). Figure 1a The NTN shown may be a transparent payload-based NTN. 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 an LEO satellite and / or an MEO satellite.

[0068] The communication node 120 may include a communication node located at a ground location (e.g., a user equipment (UE) or a terminal) and a communication node located in non-terrestrial space (e.g., an aircraft, 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 provide communication services to the communication node 120 using one or more beams. The shape of the coverage area of the beam of the satellite 110 may be elliptical or circular.

[0069] In the non-terrestrial network, the following three types of service links may be supported.

[0070] - Earth-fixed: The service link may be provided by a beam that continuously covers the same geographical area all the time (e.g., a geosynchronous orbit (GSO) satellite).

[0071] - Quasi-earth-fixed: The service link may be provided by a beam that covers a geographical area during a defined period and by a beam that covers another geographical area during another period (e.g., a non-GSO (NGSO) satellite forming a steerable beam).

[0072] - Earth-moving: The service link can be provided by a beam moving on the Earth's surface (e.g., an NGSO satellite forming a fixed beam or a non-maneuverable beam).

[0073] Communication node 120 can perform communication with satellite 110 (e.g., downlink communication and uplink communication) using 4G communication technology, 5G communication technology, and / or 6G communication technology. Communication between satellite 110 and communication node 120 can be performed using the NR-Uu interface and / or 6G-Uu interface. When dual connectivity (DC) is supported, communication node 120 can be connected to other base stations (e.g., base stations supporting 4G, 5G, and / or 6G functions) as well as satellite 110, and perform DC operations based on the technologies defined in the 4G, 5G, and / or 6G technical specifications.

[0074] Gateway 130 can be located at a ground location, and a feeder link can be established between satellite 110 and gateway 130. The feeder link can be a radio link. Gateway 130 can be referred to as a "non-terrestrial network (NTN) gateway". Communication between satellite 110 and gateway 130 can be performed based on the NR-Uu interface, 6G-Uu interface, or satellite radio interface (SRI). Gateway 130 can be connected to data network 140. There can be a "core network" between gateway 130 and data network 140. In this case, gateway 130 can be connected to the core network, and the core network can be connected to data network 140. The core network can support 4G communication technology, 5G communication technology, and / or 6G communication technology. For example, the core network can include an access and mobility management function (AMF), a user plane function (UPF), a session management function (SMF), etc. Communication between gateway 130 and the core network can be performed based on the NG-C / U interface or 6G-C / U interface.

[0075] As Figure 1b shown in the exemplary embodiments of

[0076] Figure 1b is a conceptual diagram showing a second exemplary embodiment of a non-terrestrial network.

[0077] As Figure 1bAs shown, the gateway can be connected to the base station, the base station can be connected to the core network, and the core network can be connected to the data network. Each of the base station and the core network can support 4G communication technology, 5G communication technology, and / or 6G communication technology. The communication between the gateway and the base station can be performed based on the NR-Uu interface or the 6G-Uu interface, and the communication between the base station and the core network (e.g., AMF, UPF, SMF, etc.) can be performed based on the NG-C / U interface or the 6G-C / U interface.

[0078] Figure 2a is a conceptual diagram showing a third exemplary embodiment of the non-terrestrial network.

[0079] As Figure 2a shown, the non-terrestrial network can include a first satellite 211, a second satellite 212, a communication node 220, a gateway 230, a data network 240, etc. Figure 2a The NTN shown can be a regenerative payload-based NTN. For example, each of the satellites 211 and 212 can perform regenerative operations (e.g., demodulation, decoding, re-encoding, re-modulation, and / or filtering operations) on the payload received from other entities (e.g., the communication node 220 or the gateway 230), and transmit the regenerated payload.

[0080] Each of the satellites 211 and 212 can be a LEO satellite, a MEO satellite, a GEO satellite, a HEO satellite, or a UAS platform. The UAS platform can include a HAPS. The satellite 211 can be connected to the satellite 212, and an inter-satellite link (ISL) can be established between the satellite 211 and the satellite 212. The ISL can operate in the RF band or the optical band. The ISL can be established optionally. The communication node 220 can include a terrestrial communication node (e.g., a UE or a terminal) and a non-terrestrial communication node (e.g., an aircraft or a drone). A service link (e.g., a radio link) can be established between the satellite 211 and the communication node 220. The satellite 211 can provide communication services to the communication node 220 using one or more beams.

[0081] The communication node 220 can perform communication (e.g., downlink communication or uplink communication) with the satellite 211 using 4G communication technology, 5G communication technology, and / or 6G communication technology. The communication between the satellite 211 and the communication node 220 can be performed using the NR-Uu interface or the 6G-Uu interface. When DC is supported, the communication node 220 can be connected to other base stations (e.g., base stations supporting 4G, 5G, and / or 6G functions) as well as the satellite 211, and can perform DC operations based on the technologies defined in the 4G, 5G, and / or 6G technical specifications.

[0082] The gateway 230 can be located at a ground position. A feeder link can be established between the satellite 211 and the gateway 230, and a feeder link can be established between the satellite 212 and the gateway 230. The feeder link can be a radio link. When no ISL is established between the satellite 211 and the satellite 212, the feeder link between the satellite 211 and the gateway 230 can be established compulsorily. The communication between each of the satellite 211 and the satellite 212 and the gateway 230 can be performed based on the NR-Uu interface, the 6G-Uu interface, or the SRI. The gateway 230 can be connected to the data network 240.

[0083] As Figure 2b and Figure 2c shown in the exemplary embodiments of, there can be a "core network" between the gateway 230 and the data network 240.

[0084] Figure 2b is a conceptual diagram showing a fourth exemplary embodiment of a non-terrestrial network, Figure 2c is a conceptual diagram showing a fifth exemplary embodiment of a non-terrestrial network.

[0085] As Figure 2b and Figure 2c shown, the gateway can be connected to the core network, and the core network can be connected to the data network. The core network can support 4G communication technology, 5G communication technology, and / or 6G communication technology. For example. The core network can include AMF, UPF, SMF, etc. The communication between the gateway and the core network can be performed based on the NG-C / U interface or the 6G-C / U interface. The functions of the base station can be performed by the satellite. That is, the base station can be located on the satellite. The payload can be processed by the base station located on the satellite. The base stations located on different satellites can be connected to the same core network. One satellite can have one or more base stations. In Figure 2b the non-terrestrial network of, it may not be possible to establish an ISL between satellites, while in Figure 2c the non-terrestrial network of, an ISL between satellites can be established.

[0086] On the other hand, the entities (such as satellites, base stations, UEs, communication nodes, gateways, etc.) constituting the Figure 1a , Figure 1b , Figure 2a , Figure 2b and / or Figure 2c shown non-terrestrial network can be configured as follows. In the present invention, the entity can be called a communication node.

[0087] Figure 3 is a block diagram showing a first exemplary embodiment of a communication node constituting a non-terrestrial network.

[0088] As Figure 3As shown, the communication node 300 may include at least one processor 310, a memory 320, and a transceiver 330 connected to a network to perform 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. Components included in the communication node 300 may be connected via a bus 370 to communicate with each other.

[0089] However, each component included in the communication node 300 may be connected to the processor 310 via a separate interface or a separate bus instead of the common bus 370. For example, the processor 310 may be connected to at least one of the memory 320, the transceiver 330, the input interface device 340, the output interface device 350, and the storage device 360 via a dedicated interface.

[0090] The processor 310 may execute at least one instruction 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 on which a method according to an exemplary embodiment of the present invention is executed. Each of the memory 320 and the storage device 360 may be configured as at least one of a volatile storage medium and a non-volatile storage medium. For example, the memory 320 may be configured with at least one of a read-only memory (ROM) and a random access memory (RAM).

[0091] On the other hand, a communication node that performs communication in a communication network (e.g., a non-terrestrial network) may be configured as follows. Figure 4 The shown communication node may be Figure 3 a specific exemplary embodiment of the shown communication node.

[0092] Figure 4 is a block diagram showing a first exemplary embodiment of a communication node that performs communication.

[0093] As Figure 4 shown, 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 send a signal to the second communication node 400b. A 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).

[0094] The transmitting processor 411 may generate data symbols by performing processing operations on data (e.g., encoding operations, symbol mapping operations, etc.). The transmitting processor 411 may generate control symbols by performing processing operations on control information (e.g., encoding operations, symbol mapping operations, etc.). Additionally, the transmitting processor 411 may generate synchronization / reference symbols for synchronization signals and / or reference signals.

[0095] The Tx MIMO processor 412 may perform spatial processing operations (e.g., precoding operations) on the data symbols, control symbols, and / or synchronization / reference symbols. The output of the Tx MIMO processor 412 (e.g., symbol stream) may be provided to the modulators (MOD) included in the transceivers 413a to 413t. The modulator may generate modulated symbols by performing processing operations on the symbol stream, and may generate signals by performing additional processing operations on the modulated symbols (e.g., analog conversion operations, amplification operations, filtering operations, upconversion operations, etc.). The signals generated by the modulators of the transceivers 413a to 413t may be transmitted via the antennas 414a to 414t.

[0096] The signals transmitted by the first communication node 400a may be received at the antennas 464a to 464r of the second communication node 400b. The signals received at the antennas 464a to 464r may be provided to the demodulators (DEMOD) included in the transceivers 463a to 463r. The demodulator (DEMOD) may obtain samples by performing processing operations on the signals (e.g., filtering operations, amplification operations, downconversion operations, digital conversion operations, etc.). The demodulator may perform additional processing operations on the samples to obtain symbols. The MIMO detector 462 may perform MIMO detection operations on the symbols. The receiving processor 461 may perform processing operations on the symbols (e.g., deinterleaving operations, decoding operations, etc.). The output of the receiving processor 461 may be provided to the data sink 460 and the controller 466. For example, data may be provided to the data sink 460, and control information may be provided to the controller 466.

[0097] On the other hand, the second communication node 400b may transmit signals to the first communication node 400a. The transmitting processor 468 included in the second communication node 400b may receive data (e.g., data units) from the data source 467 and perform processing operations on the data to generate data symbols. The transmitting processor 468 may receive control information from the controller 466 and perform processing operations on the control information to generate control symbols. Additionally, the transmitting processor 468 may generate reference symbols by performing processing operations on reference signals.

[0098] The Tx MIMO processor 469 may perform spatial processing operations (e.g., precoding operations) on data symbols, control symbols, and / or reference symbols. The output of the Tx MIMO processor 469 (e.g., symbol stream) may be provided to a modulator (MOD) included in transceivers 463a to 463t. The modulator may generate modulated symbols by performing processing operations on the symbol stream, and may generate a signal by performing additional processing operations on the modulated symbols (e.g., analog conversion operations, amplification operations, filtering operations, upconversion operations, etc.). The signals generated by the modulators of transceivers 463a to 463t may be transmitted via antennas 464a to 464t.

[0099] The signals transmitted by the second communication node 400b may be received at antennas 414a to 414r of the first communication node 400a. The signals received at antennas 414a to 414r may be provided to a demodulator (DEMOD) included in transceivers 413a to 413r. The demodulator may obtain samples by performing processing operations on the signals (e.g., filtering operations, amplification operations, downconversion operations, digital conversion operations, etc.). The demodulator may perform additional processing operations on the samples to obtain symbols. The MIMO detector 420 may perform MIMO detection operations on the symbols. The receive processor 419 may perform processing operations on the symbols (e.g., deinterleaving operations, decoding operations, etc.). The output of the receive processor 419 may be provided to the data sink 418 and the controller 416. For example, data may be provided to the data sink 418, and control information may be provided to the controller 416.

[0100] The memories 415 and 465 may store data, control information, and / or program code. The scheduler 417 may perform scheduling operations for communication. Figure 4 The illustrated processors 411, 412, 419, 461, 468, and 469, and the controllers 416 and 466 may be Figure 3 the illustrated processor 310, and may be used to perform the methods described in the present invention.

[0101] Figure 5a is a block diagram showing a first exemplary embodiment of a transmission path, Figure 5b is a block diagram showing a first exemplary embodiment of a reception path.

[0102] As Figure 5a and Figure 5bAs shown, the transmit path 510 can be implemented in a communication node that transmits a signal, and the receive path 520 can be implemented in a communication node that receives a signal. The transmit path 510 can include a channel coding and modulation block 511, a serial-to-parallel (S-to-P) block 512, an N-point inverse fast Fourier transform (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 receive path 520 can include a down-converter (DC) 521, a CP removal block 522, an S-to-P block 523, an N-point FFT block 524, a P-to-S block 525, and a channel decoding and demodulation block 526. Here, N can be a natural number.

[0103] In the transmit path 510, information bits can be input to the channel coding and modulation block 511. The channel coding and modulation block 511 can perform an encoding operation (e.g., a low-density parity check (LDPC) encoding operation, a polar encoding operation, etc.) and a modulation operation (e.g., Quadrature Phase Shift Keying (QPSK), Quadrature Amplitude Modulation (QAM), etc.) on the information bits. The output of the channel coding and modulation block 511 can be a sequence of modulated symbols.

[0104] The S-to-P block 512 can convert the frequency-domain modulated symbols into a parallel symbol stream to generate N parallel symbol streams. N can be the IFFT size or the FFT size. The N-point IFFT block 513 can generate a time-domain signal by performing an IFFT operation on the N parallel symbol streams. The P-to-S block 514 can convert the output of the N-point IFFT block 513 (e.g., a parallel signal) into a serial signal to generate a serial signal.

[0105] The CP addition block 515 can insert a CP into the signal. The UC 516 can up-convert the frequency of the output of the CP addition block 515 to a radio frequency (RF) frequency. In addition, the output of the CP addition block 515 can be filtered in the baseband before up-conversion.

[0106] The signal transmitted from the transmission path 510 can be input into the reception path 520. The operations in the reception path 520 can be operations opposite to those in the transmission path 510. The DC 521 can down-convert the frequency of the received signal to the baseband frequency. The CP removal block 522 can remove the CP from the signal. The output of the CP removal block 522 can be a serial signal. The S-to-P block 523 can convert the serial signal into a parallel signal. The N-point FFT block 524 can generate N parallel signals by performing the FFT algorithm. The P-to-S block 525 can convert the parallel signal into a modulated symbol sequence. The channel decoding and demodulation block 526 can perform the demodulation operation on the modulated symbols and can recover the data by performing the decoding operation on the result of the demodulation operation.

[0107] In Figure 5a and Figure 5b discrete Fourier transform (DFT) and inverse DFT (IDFT) can be used instead of FFT and IFFT. Figure 5a and Figure 5b Each of the blocks (e.g., components) in Figure 5a and Figure 5b can be implemented by at least one of hardware, software, or firmware. For example, Figure 5a and Figure 5b some of the blocks in

[0108] On the other hand, the NTN reference scenario can be defined as shown in Table 1 below.

[0109] [Table 1]

[0110] NTN shown in Figure 1 NTN shown in Figure 2 GEO Scenario A Scenario B LEO (Steerable Beam) Scenario C1 Scenario D1 LEO (Beam Moving with Satellite) Scenario C2 Scenario D2

[0111] When Figure 1a and / or Figure 1b the satellite 110 in the NTN shown is a GEO satellite (e.g., a GEO satellite supporting the transparent function), this can be called "Scenario A". When Figure 2a , Figure 2b and / or Figure 2c the satellites 211 and 212 in the NTN shown are GEO satellites (e.g., GEOs supporting the regeneration function), this can be called "Scenario B".

[0112] When Figure 1a and / or Figure 1bWhen the satellite 110 in the NTN shown is a LEO satellite with steerable beams, this can be referred to as "Scenario C1". When Figure 1a and / or Figure 1b the satellite 110 in the NTN shown is a LEO satellite with beams that move with the satellite, this can be referred to as "Scenario C2". When Figure 2a 、 Figure 2b and / or Figure 2c the satellites 211 and 212 in the NTN shown are LEO satellites with steerable beams, this can be referred to as "Scenario D1". When Figure 2a 、 Figure 2b and / or Figure 2c the satellites 211 and 212 in the NTN shown are LEO satellites with beams that move with the satellite, this can be referred to as "Scenario D2".

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

[0114] [Table 2]

[0115]

[0116]

[0117] In addition, in the scenarios defined in Table 1, the delay constraints can be defined as shown in Table 3 below.

[0118] [Table 3]

[0119]

[0120] Figure 6a is a conceptual diagram showing a first exemplary implementation of the user plane protocol stack in a non-terrestrial network based on a transparent payload, Figure 6b is a conceptual diagram showing a first exemplary implementation of the control plane protocol stack in a non-terrestrial network based on a transparent payload.

[0121] As Figure 6a and Figure 6b shown, user data can be sent and received between the UE and the core network (e.g., UPF), and control data (e.g., control information) can be sent and received between the UE and the core network (e.g., AMF). Each of the user data and the control data can be sent and received via the satellite and / or the gateway. Figure 6a The protocol stack of the user plane shown can be applied in the same or similar way as a 6G communication network. Figure 6b The protocol stack of the control plane shown can be applied in the same or similar way as a 6G communication network.

[0122] Figure 7ais a conceptual diagram showing a first exemplary implementation of the user plane protocol stack in a non-terrestrial network based on regenerated payloads, Figure 7b is a conceptual diagram showing a first exemplary implementation of the control plane protocol stack in a non-terrestrial network based on regenerated payloads.

[0123] As Figure 7a and Figure 7b shown, each of the user data and control data (e.g., control information) can be sent and received through an interface between the UE and the satellite (e.g., base station). The user data can refer to user protocol data units (PDUs). The protocol stack of the satellite radio interface (SRI) can be used to send and receive user data and / or control data between the satellite and the gateway. The user data can be sent and received between the satellite and the core network through a General Packet Radio Service (GPRS) Tunneling Protocol (GTP)-U tunnel.

[0124] On the other hand, in a non-terrestrial network, the base station can send system information (e.g., SIB19) including satellite assistance information for NTN access. The UE can receive the system information (e.g., SIB19) from the base station, identify the satellite assistance information included in the system information, and perform communication (e.g., non-terrestrial communication) based on the satellite assistance information. SIB19 can include the information elements defined in Table 4 below.

[0125] [Table 4]

[0126]

[0127] The NTN-Config defined in Table 4 can include the information elements defined in Table 5 below.

[0128] [Table 5]

[0129]

[0130]

[0131] [Table 6]

[0132]

[0133] A non-terrestrial network can support voice call services. In a non-terrestrial network, a terminal can send packets (e.g., voice packets) to a base station via an uplink channel (e.g., a physical uplink shared channel (PUSCH)). In a non-terrestrial network based on transparent payloads, the base station can be located on the ground. In this case, the packets sent by the terminal can be delivered to the base station through the path of (terminal → satellite → gateway → base station), and the packets sent by the base station can be delivered to the terminal through the path of (base station → gateway → satellite → terminal). In a non-terrestrial network based on regenerative payloads, the base station can be located on a satellite. In this case, the communication between the terminal and the base station can represent the communication between the terminal and the satellite. In the present invention, a packet can refer to a voice packet, a video packet, etc.

[0134] In a non-terrestrial network, very large propagation delays may occur. To meet the low latency requirements of voice call services in a non-terrestrial network, voice packets can be repeatedly retransmitted. The repeated retransmission of voice packets can improve transmission reliability. HARQ retransmission operations may not be applied in voice call services.

[0135] To encode packets (e.g., voice packets) in a non-terrestrial network, an adaptive multi-rate (AMR) codec can be utilized. The AMR codec can support various modes, as shown in Table 7 below. AMR_4.75 can be supported in a non-terrestrial network.

[0136] [Table 7]

[0137] Mode Bit Rate (kbits / s) AMR_12.20 12.20 AMR_10.20 10.20 AMR_7.95 7.95 AMR_7.40 7.40 AMR_6.70 6.70 AMR_5.90 5.90 AMR_5.15 5.15 AMR_4.75 4.75 AMR_SID 1.80

[0138] When voice data (e.g., payload) is generated in a terminal, the medium access control (MAC) layer of the terminal can generate a MAC protocol data unit (MPDU) including the voice data and deliver the MPDU to the physical (PHY) layer of the terminal. The PHY layer of the terminal can receive the MPDU from the MAC layer of the terminal, generate a physical PDU (PPDU) based on the MPDU, and send the PPDU to the base station. The PPDU including voice data can be a voice packet. The structure of the MPDU including voice data can be as shown in Table 8 below.

[0139] [Table 8]

[0140]

[0141] The AMR payload can be voice data. A PPDU (e.g., a voice packet) can include a PHY header, an MPDU specified in Table 8, and a cyclic redundancy check (CRC) field. The size of the CRC field (e.g., the number of CRC bits) can be 16 bits. The generation period (or transmission period) of a voice packet (e.g., an MPDU including voice data) can be 20 ms. Since the size of the header in a voice packet is significant, the overhead caused by the header can be large. This overhead may reduce the transmission efficiency, so a method to address this problem is needed.

[0142] On the other hand, in a traditional terrestrial network, handover may occur due to the individual movement of a terminal. In other words, according to the individual movement of a terminal, the handover process may be executed on each terminal. In this case, when the handover process occurs, the handover process may include at least one of a handover-related signal strength measurement, a handover-related signal strength report, a handover request, a handover confirmation, or a handover command process. In this case, signaling overhead may occur in the satellite when processing the handover confirmation or handover command process.

[0143] On the other hand, in a non-terrestrial network, handover may occur due to the movement of a satellite. Handover in a non-terrestrial network may occur simultaneously from a large number of terminals. Additionally, due to the high speed of the satellite, handover in a non-terrestrial network may occur frequently. Therefore, since the satellite and the base station in a non-terrestrial network process handovers of a large number of terminals simultaneously, signaling overhead may occur. The present invention proposes a group-based handover processing method as a method for reducing the overhead that occurs when processing handovers in a non-terrestrial network.

[0144] The group-based handover processing method can include a method for group configuration and a method for reducing handover overhead based on group configuration. In this case, since handover occurs according to the movement of the satellite in a non-terrestrial network environment, the group-based handover processing method can consider the movement of the satellite. The movement of the satellite can vary according to the satellite system in a non-terrestrial network. Additionally, the satellite system in a non-terrestrial network can vary according to the movement of the satellite. In this case, the area supported by the satellite for providing services can be referred to as a beam point or a beam area. The beam area can be referred to as a beam coverage area. The beam coverage area generated by the satellite can vary on the ground according to the movement of the satellite. According to the change of the beam coverage area in a non-terrestrial network, the satellite system can be divided into two scenarios. These two scenarios can include an earth fixed beam (EFB) scenario and an earth moving beam (EMB) scenario. In this case, the present invention can apply different group configuration methods to the EFB scenario and the EMB scenario.

[0145] Figure 8 It is a conceptual diagram for describing the EFB.

[0146] As Figure 8 shown, the beam of the satellite can have EFB characteristics. Figure 8 It can represent the characteristic of maintaining cell coverage regardless of the movement of the satellite in the EFB environment.

[0147] In the EFB environment, even when the satellite (located at 810 or 820) moves, the existing beam coverage on the ground 860 can be maintained. The beam coverage can be referred to as the cell area (cell coverage) on the ground. In the EFB environment, the satellite at 810 or 820 can fixedly maintain the cell area through beam steering or beam switching. As the satellite moves, a new satellite can provide services to the cell area. When the new satellite starts to provide services to the cell area, the elevation angle between the cell area and the new satellite can be the smallest. The elevation angle can increase as the satellite moves. After the elevation angle increases, as the satellite moves further, the elevation angle may decrease again. In this case, the distance between the satellite and the cell can decrease or increase according to the change of the elevation angle.

[0148] Figure 9 It is a conceptual diagram for describing the EMB.

[0149] As Figure 9 shown, the beam of the satellite can have EMB characteristics. Figure 9 It can represent the characteristic that the beam coverage changes according to the movement of the satellite in the EMB environment.

[0150] In the EMB environment, when the satellite (located at 910 or 920) moves, the cell area 960 or the cell area 970 on the ground can change according to the movement of the satellite. Therefore, the satellite serving the terminals in a specific area can change continuously. In this case, the terminals included in the beam coverage of a specific satellite can have different data service times according to the position of the beam coverage. In other words, the remaining cell time of the terminal can be different according to the position of the terminal. The remaining cell time can refer to the remaining time that the terminal is served in the corresponding cell according to the position of the terminal within the beam coverage. In other words, the remaining cell time can be the time when communication services can be provided to the terminal in the cell where the terminal is located. When the remaining cell time (e.g., the remaining cell service time) expires, the terminal can perform the process of (re)selecting another cell. The remaining cell time can be referred to as the remaining time.

[0151] Figure 10a It is a conceptual diagram showing the first exemplary embodiment of the handover process.

[0152] As Figure 10aAs shown, in an EFB environment, satellites (i.e., the first satellite, the second satellite) can form cell coverage. In this case, the beam coverage can be formed by at least one beam region (e.g., a beam point). A beam region can refer to the region covered by one beam. In other words, a satellite can form one or more beam regions (beam points).

[0153] In an EFB environment, all terminals located in the same beam region can request a handover process from the satellite at the same or similar time. When terminals are included in the same beam region, the terminals can have the same remaining cell time value. With the same remaining cell time value, the satellite can configure all terminals in the same beam region as the same group.

[0154] The satellite can send a paging message to terminals in one beam region. The satellite can send one paging message to terminals in multiple beam regions. The paging message can include a group identifier. Different group identifiers can be assigned to each beam region. For example, the satellite can send a paging message to 5 beam regions. In this case, the group identifiers of the terminal groups belonging to different beam regions among the 5 beam regions can be different from each other. Terminals in one beam region can receive the same group identifier from the satellite.

[0155] Figure 10b It is a conceptual diagram showing a second exemplary embodiment of the handover process.

[0156] As Figure 10a and Figure 10b shown, in an EFB-based non-terrestrial network (hereinafter referred to as the "EFB non-terrestrial network"), each of the first satellite and the second satellite can move over time (e.g., from a first time to a second time) and can support EFB. The second time can be after the first time. The handover process can be divided into an intra-SAT (intra-satellite) handover process and an inter-SAT (inter-satellite) handover process. Each of the intra-SAT handover process and the inter-SAT handover process can be a conventional handover process or a conditional handover (CHO) process. In the intra-SAT handover process, a terminal can perform a handover process in the cell of the same satellite. In other words, the intra-SAT handover process can be performed by beam switching at the same satellite. For example, in the intra-SAT handover process, all terminals connected to the first cell of the first satellite can switch to the second cell of the first satellite. In this case, all terminals can switch to the second cell at the same or similar time. EFB can be supported by beam steering within the same satellite.

[0157] During the satellite handover process, the terminal can perform the handover process between satellites. During the satellite handover process, all terminals connected to the first cell of the first satellite can be handed over to the second cell of the second satellite. In this case, all terminals can be handed over to the second satellite at the same or similar time. The handover process performed during the time period from the first time to the second time can be a satellite handover process. EFB can be supported by a new cell of a new satellite (e.g., the second satellite).

[0158] Due to the high altitude in the non-terrestrial network, the handover process based on the reference signal received power (RSRP) may not be effective. Therefore, a handover process suitable for the non-terrestrial network may be required. Even when the satellites in the EFB environment move in the non-terrestrial network, the cell area on the ground can be maintained. In other words, the satellite can support a fixed cell area. The intra-satellite handover process and / or the inter-satellite handover process can be performed simultaneously for the terminals within the same cell (e.g., all terminals or some terminals). An efficient handover process considering the above characteristics of the EFB non-terrestrial network may be required.

[0159] Figure 11 It is a conceptual diagram showing a third exemplary embodiment of the handover process.

[0160] As Figure 11 shown, in the EMB environment, terminals included in the same beam area can have different remaining cell times according to the positions of the terminals. When the remaining cell times of the respective terminals are different, the time at which each terminal requests a handover can be different. For example, the first terminal 1121, the second terminal 1122, and the third terminal 1123 can be included in one beam area (e.g., beam area 12). The remaining cell time of the first terminal 1121 can be the longest compared to other terminals. In this case, the terminals belonging to the same beam area can perform the handover in ascending order of the remaining cell time values.

[0161] On the other hand, regardless of the remaining cell time, the target satellite of the terminal can change according to the position of the terminal. For example, the third terminal can be included in the beam area 12, but can also be included in the beam area 14. The second terminal can be included in the beam areas 12, 13, and 15. Therefore, the third terminal can perform the handover process to the target satellite supporting the beam area 14. The second terminal can perform the handover process to the target satellite supporting the beam area 15.

[0162] The satellite can configure a group for the terminal based on the remaining cell time value and the beam region determination information, so that the terminals within the same beam region can perform the handover process through common signaling. The beam region determination information can refer to the information used to determine one beam region that supports the terminal when the terminal is included in multiple beam regions. The beam region determination information can include at least one of the position information of the terminal, the ephemeris information of the satellite, or the identifier (ID) of the target satellite. The position information of the terminal can include at least one of the most recent position information of the terminal, the past position information, the moving speed, or the moving direction. The moving speed and the moving direction of the terminal can be determined based on the most recent position information and / or the past position information of the terminal. The remaining cell time and / or the ID of the target satellite can be updated based on the position information of the terminal.

[0163] On the other hand, according to the present invention, the beam region can be determined in an environment where a terrestrial network and a non-terrestrial network coexist. A method for determining the beam region in an environment where a terrestrial network and a non-terrestrial network coexist will be described later.

[0164] The satellite can send a position information request message to the terminal to obtain the position information of the terminal. In addition, the satellite can configure the terminal through an RRC configuration message so that the terminal periodically sends their position information to the satellite. In the present invention, only the most recent position information of the terminal can be used.

[0165] Figure 12 It is a sequence diagram showing a first exemplary embodiment of the handover process.

[0166] As Figure 12 shown, the handover process is shown. In Figure 12 , the satellite can refer to the base station. In other words, the first satellite can represent the first base station. In addition, the second satellite can represent the second base station.

[0167] The terminal can measure the channel state information (CSI) to perform the handover. The first terminal can send a CSI measurement report message (S1211) to the first satellite. The CSI measurement report message can include the CSI. The first satellite can receive the CSI measurement report message sent by the first terminal. The Nth terminal can send a CSI measurement report message (S1212) to the first satellite. The first satellite can receive the CSI measurement report message sent by the Nth terminal.

[0168] The first satellite may initiate a handover for each terminal based on the CSI measurement report message of each terminal (S1221). The first satellite may send a handover request message for each terminal to the second satellite (S1231, S1232). The second satellite may receive the handover request message sent by the first satellite. The second satellite may determine whether to approve the handover for each terminal based on the received handover request message. When the second satellite approves the handover, the second satellite may send a handover request confirmation message for each terminal to the first satellite (S1241, S1242). The first satellite may receive the handover request confirmation message sent by the second satellite. The first satellite may send a handover command message to the first terminal. The first terminal may receive the handover command message sent by the first satellite (S1251). The first satellite may send a handover command message to the Nth terminal. The Nth terminal may receive the handover command message sent by the first satellite (S1252). When the first terminal receives the handover command message sent by the first satellite, the first terminal may perform an access procedure to the second satellite. In other words, the first terminal may perform a random access to the second satellite (i.e., the target satellite), and may send a handover completion message to the second satellite. When the Nth terminal receives the handover command message sent by the first satellite, the Nth terminal may perform an access procedure to the second satellite. In other words, the terminal may perform a random access to the second satellite (i.e., the target satellite), and may send a handover completion message to the second satellite.

[0169] Figure 13 It is a sequence diagram showing a second exemplary embodiment of the handover process.

[0170] As Figure 13 shown, the process performed by the first satellite may be performed by the first base station. The process performed by the first satellite may be performed by the first satellite and the first base station. The process performed by the second satellite may be performed by the second base station. The process performed by the second satellite may be performed by the second satellite and the second base station. The first base station or the second base station may be a base station in a non-terrestrial network based on a transparent payload or a base station in a non-terrestrial network based on a regenerative payload. In a non-terrestrial network based on a transparent payload, the base station may be located on the ground. The handover process of the present invention may be performed in a non-terrestrial network based on a regenerative payload. The handover process of the present invention may be performed in a non-terrestrial network based on a transparent payload.

[0171] The first satellite may configure a group (S1310) for terminals within a cell area or beam area supported by the first satellite. Terminals in the cell area may refer to terminals included in at least one beam area. Thus, terminals within the cell area may be included in different beam areas supported by the first satellite. The first terminal to the Nth terminal may be included in the first beam area, and the first satellite may configure the first terminal to the Nth terminal included in the first beam area as the first group. The (N + 1)th terminal to the Mth terminal may be included in the second beam area, and the first satellite may configure the (N + 1)th terminal to the Mth terminal included in the second beam area as the second group.

[0172] The first satellite may configure at least one group (S1310) for terminals within a beam area supported by the first satellite. For example, the first terminal to the Nth terminal may be included in the first beam area. The first satellite may configure the first terminal to the Nth terminal as the first group and may configure the (N + 1)th terminal to the Mth terminal as the second group. In this case, the first satellite may send group configuration information to each terminal via RRC signaling. The group configuration information may include at least one of a group identifier (group ID), an identifier of a terminal belonging to the group, or CSI configuration information (e.g., a CSI measurement sequence, CSI measurement information, CSI reporting period, and / or CSI reporting time of a terminal for measuring CSI). All terminals in the same group may apply a single common signaling.

[0173] When the first satellite configures a group for a terminal, the terminals in the group may perform a handover process. To perform the handover process, the terminal may perform a CSI measurement process and a CSI reporting process. In the present invention, only a part of the terminals belonging to the same group may perform the CSI measurement process and the CSI reporting process.

[0174] When there is one group for a terminal, the first satellite may set the number of terminals that perform the CSI measurement process and the CSI reporting process within the group. The number of terminals that perform the CSI measurement process and the CSI reporting process in the group may be referred to as K. The number K of terminals that perform the CSI measurement process and the CSI reporting process may be determined by a terminal selection method of the satellite. The terminal selection method of the satellite may include a method of random selection and a method of selection based on a remaining cell time value.

[0175] The remaining cell time of terminals included in the beam area may fall within a time range configured by the satellite. The number of terminals whose remaining cell time falls within the time range configured by the satellite may be referred to as K.

[0176] When K is 1, it can indicate that a terminal in the group performs a CSI measurement process and a CSI report process. Therefore, when K is 1, the overhead caused by the handover process performed by the terminal in the group can be the lowest. Additionally, the first satellite can set K to at least 2 or greater. The first satellite can configure all K terminals to perform a CSI measurement process and a CSI report process. The first satellite can also configure the K terminals to perform the CSI measurement process and the CSI report process sequentially in order. For example, when the first satellite sends a group indicator to a terminal, the first satellite can send at least one of a group identifier, a flag indicating the order of application, a CSI measurement period, a CSI report period, a CSI measurement time, or a CSI report time to the terminal.

[0177] In addition, the first satellite can configure different report times for each terminal performing a CSI measurement process and a CSI report process. The first satellite can configure the CSI measurement time and the CSI report time for each terminal through a modulo operation based on at least one of a cell-radio network temporary identifier (C-RNTI), a remaining cell time, a current time, or a system frame number (SFN) value.

[0178] Furthermore, the first satellite can change the CSI measurement period and the CSI report period based on the remaining cell time value. For example, when the remaining cell time is small, the first satellite can set the CSI measurement period and the CSI report period to be short. Additionally, when the remaining cell time is large, the first satellite can set the CSI measurement period and the CSI report period to be long.

[0179] When there are two or more groups for terminals, the first satellite can set K for each group. In this case, the first satellite can set K differently for each group. By setting K differently for each group, the first satellite can control the number of terminals performing a CSI measurement process and a CSI report process in the group that requires a handover process.

[0180] On the other hand, when the first satellite configures a group for terminals in a cell area or a beam area supported by the first satellite, the first satellite can determine the beam area for the terminals.

[0181] Figure 15 is a conceptual diagram showing a first exemplary embodiment of a beam area determination method.

[0182] As Figure 15 shown, a method for determining the beam area of a satellite when a terminal belongs to a terrestrial network area and a non-terrestrial network area is shown. Figure 15It is possible to group non-terrestrial network terminals based on tracking area information of a terrestrial network. According to the present invention, when configuring groups for terminals in an environment where a terrestrial network and a non-terrestrial network coexist, beam regions can be determined by considering the tracking area of each terminal. In other words, when configuring groups for terminals, the present invention can first consider the tracking area of each terminal in the terrestrial network environment and then configure the groups. Figure 15 Two beam regions are shown. The two beam regions may refer to beam region 1510 and beam region 1520.

[0183] The method for configuring groups for terminals based on the tracking area may include a method for determining beam regions. The method for determining beam regions may consider the tracking area. When considering the tracking area, the satellite may consider the proportion of the tracking area occupying the beam region. In other words, the satellite may consider the degree of overlap between each tracking area and each beam region. For example, since tracking area A occupies a larger portion of beam region X than beam region Y, the satellite may determine that the terminals in tracking area A belong to beam region 1510. The satellite may send the group identifier X of beam region 1510 to the terminals in tracking area A. Since tracking area C occupies a larger portion of beam region Y than beam region X, the satellite may determine that the terminals in tracking area C belong to beam region 1520. The satellite may send the group identifier Y of beam region 1520 to the terminals in tracking area C.

[0184] The satellite may configure groups by sending the group identifier X to the terminals in tracking area A and tracking area B. The satellite may configure groups by sending the group identifier Y to the terminals in tracking area C.

[0185] On the other hand, referring again to Figure 13 , the first satellite may send group configuration information to each terminal (S1321). The group configuration information may include a group indicator. In other words, the first satellite may send the group configuration information for the first group to each terminal (S1321). The first group may include the first terminal to the Nth terminal. Additionally, the first satellite may send the group configuration information for the second group to each terminal. The second group may include the (N + 1)th terminal to the Mth terminal.

[0186] When the first satellite sends group configuration information to a terminal, the first satellite may send the group information through at least one of RRC signaling, system information, medium access control (MAC) control element (CE), or downlink control information (DCI). The first satellite may select a signaling scheme based on the frequency of sending group configuration information to the terminal. For example, when the first satellite frequently sends group configuration information to a terminal, the first satellite may send the group configuration information through RRC signaling. When the first satellite does not frequently send group configuration information to a terminal, the first satellite may send the group configuration information through system information.

[0187] On the other hand, when the first satellite sends group configuration information to each terminal, the first satellite may send information on whether to perform the CSI measurement process and the CSI reporting process. For example, the first satellite may send information (or an indicator) instructing each terminal to perform the CSI measurement process and the CSI reporting process. Additionally, the first satellite may send information (or an indicator) instructing each terminal not to perform the CSI measurement process and the CSI reporting process. The first satellite may send information (or an indicator) instructing to perform the CSI measurement process and the CSI reporting process only to the terminals that perform the CSI measurement process and the CSI reporting process. The first satellite may not send any information to the terminals that do not perform the CSI measurement process and the CSI reporting process. Instead, the first satellite may not send information (or an indicator) instructing to perform the CSI measurement process and the CSI reporting process to the terminals that perform the CSI measurement process and the CSI reporting process. Additionally, the first satellite may send information (or an indicator) instructing not to perform the CSI measurement process and the CSI reporting process only to the terminals that do not perform the CSI measurement process and the CSI reporting process.

[0188] All terminals in the same group may not perform the CSI measurement process and the CSI reporting process. The terminals that perform the CSI measurement process and the CSI reporting process in the first group and the terminals that perform the CSI measurement process and the CSI reporting process in the second group may generate CSI. The terminals that perform the CSI measurement process and the CSI reporting process in the first group and the terminals that perform the CSI measurement process and the CSI reporting process in the second group may send a group-based CSI measurement report message (S1330) to the first satellite. The CSI measurement report message may include CSI.

[0189] On the other hand, due to the movement of the satellite, the group of terminals may change during the CSI measurement process and the CSI reporting process. The change in the group identifier of the terminals may be referred to as group update. In this case, the terminals that perform the CSI measurement process and the CSI reporting process may not follow the instructions for performing the CSI measurement process and the CSI reporting process sent before the group update. In other words, the terminals that perform the CSI measurement process and the CSI reporting process may stop the CSI measurement process and the CSI reporting process. Additionally, the terminals that perform the CSI measurement process and the CSI reporting process may continue to perform the CSI measurement process and the CSI reporting process. The CSI measurement report message sent from the terminals whose group has been updated may be sent to the first satellite. The first satellite may not use the CSI measurement report message sent from the terminals whose group has been updated. Additionally, the first satellite may use the CSI measurement report message sent from the terminals whose group has been updated as the CSI measurement information of the newly configured group.

[0190] The first satellite, the second satellite, and the terminal can perform a handover signaling procedure (S1340). During handover, each terminal can independently perform a CSI measurement procedure, a CSI reporting procedure, and a handover signaling procedure. Thus, the satellite can independently perform procedures such as receiving a CSI measurement report message, making a handover decision, sending a handover request message, sending a handover request confirmation message, or sending a handover command message for each terminal belonging to a cell in a non-terrestrial network environment. However, in a non-terrestrial network environment, the satellite may face the problem of having to handle a large number of handover procedures simultaneously. In this case, since handover is performed due to the movement of the satellite, terminals configured in the same group can perform the handover procedure through the same signaling.

[0191] The first satellite can perform a handover initiation procedure (S1341). In this case, the first satellite can determine handover based on the group. Additionally, when there are multiple groups, the first satellite can perform the handover initiation procedure for each group.

[0192] When initiating a handover procedure for the first group, the first satellite can send a group-based handover request message for the first group to the second satellite (S1342). The handover request message can include the IDs of the terminals in the first group and the configuration information of the terminals. In this case, the configuration information of the terminals can include common configuration information and individual configuration information. The second satellite can receive the group-based handover request message for the first group sent by the first satellite.

[0193] The second satellite can send a group-based handover request confirmation message for the first group to the first satellite (S1343). The first satellite can receive the group-based handover request confirmation message for the first group sent by the second satellite.

[0194] The first satellite can send a handover command message to all terminals in the first group (S1344). In this case, the first satellite can send a group-based handover request confirmation message for the first group to each terminal in the first group. The first satellite can send the handover request confirmation message to each terminal in the first group through a unicast, multicast, or broadcast scheme. The first satellite can send the handover command message to each terminal in the first group through a unicast, multicast, or broadcast scheme. In this case, the first satellite can send the information normally sent to the terminals in the group through a unicast, multicast, or broadcast scheme. The first satellite can send the individual information for each terminal in the first group to each terminal in the first group through individual signaling. The handover command message can include a group handover indicator. The group handover indicator can indicate whether group-based handover is applied. Through the group handover indicator, each terminal in the first group can identify whether non-group-based handover or group-based handover is applied. Each terminal in the first group can receive the handover command message sent by the first satellite.

[0195] When at least one of a handover request message, a handover request confirmation message, or a handover command message is sent, group-based signaling can be utilized. Group-based signaling can refer to using a common signaling within a group.

[0196] When receiving a handover command message sent by a first satellite, a terminal (e.g., a terminal belonging to a first group) can perform an access procedure to a second satellite. In other words, the terminal can perform random access to the second satellite (i.e., the target satellite), and the terminal can send a handover completion message to the second satellite.

[0197] Figure 14 It is a conceptual diagram showing a first exemplary embodiment of a tracking area.

[0198] As Figure 14 shown, tracking area update will be described.

[0199] The present invention proposes a method for configuring a group related to a tracking area of a terrestrial network in a coexistence scenario of a terrestrial network and a non-terrestrial network environment. In a terrestrial network environment, each tracking area can be composed of a set of one or more adjacent cells. Each cell can belong to a tracking area.

[0200] Figure 14 Three tracking areas are shown. A terminal can perform a tracking area update procedure when the tracking area changes. In Figure 14 it, the terminal can perform two tracking area updates.

[0201] The operations of the method according to an exemplary embodiment of the present invention can be implemented as a computer-readable program or code in a computer-readable recording medium. The computer-readable recording medium can include all types of recording devices that store data readable by a computer system. In addition, the computer-readable recording medium can store and execute programs or codes, which can be distributed in computer systems connected through a network and read by a computer in a distributed manner.

[0202] The computer-readable recording medium can include hardware devices specifically configured to store and execute program instructions, such as ROM, RAM, or flash memory. The program instructions can include not only machine language codes created by a compiler but also high-level language codes executable by a computer using an interpreter.

[0203] Although some aspects of the present invention have been described in the context of an apparatus, these aspects may indicate a corresponding description according to a method, and a block or apparatus may correspond to a step or a feature of a step of the method. Similarly, aspects described in the context of a method may be represented as features of a corresponding block or item or a corresponding apparatus. Some or all of the steps of the method may be performed by (or using) a hardware apparatus such as a microprocessor, a programmable computer, or an electronic circuit. In some embodiments, one or more of the most important steps of the method may be performed by such an apparatus.

[0204] In some exemplary embodiments, a programmable logic device such as a field programmable gate array may be used to perform some or all of the functions of the methods described herein. In some exemplary embodiments, a field programmable gate array may be operated with a microprocessor to perform one of the methods described herein. Generally, the methods are preferably performed by a specific hardware apparatus.

[0205] The description of the present invention is merely exemplary in nature and, thus, variations that do not depart from the essence of the present invention are intended to be within the scope of the present invention. Such variations are not to be regarded as a departure from the spirit and scope of the present invention. Accordingly, those of ordinary skill in the art will understand that various changes in form and detail may be made without departing from the spirit and scope defined by the appended claims.

Claims

1. A method for a user equipment (UE), comprising: Receiving, from a satellite, group configuration information for a group including the UE, based on a beam region supported by the satellite; Receiving, from the satellite, a group indicator indicating the group; Measuring channel state information (CSI) of the group; Reporting a message including the CSI to the satellite; And Receiving, from the satellite, a handover command message for a handover determined based on the result of measuring the CSI.

2. The method according to claim 1, wherein The group configuration information includes at least one group identifier (ID) based on the beam region.

3. The method according to claim 1, wherein When the cell remaining time falls within a time range configured by the satellite, the group configuration information includes a group ID for identifying a group including the UE having the cell remaining time, where the cell remaining time is the time for which the UE is in a state served by the beam region.

4. The method according to claim 1, further comprising: Determining a beam region that occupies the largest portion of a tracking area in a beam region supported by the satellite as the beam region associated with the tracking area.

5. The method according to claim 1, further comprising: Determining a beam region supporting the UE based on beam region determination information, where the beam region determination information includes at least one of the UE's location information, the satellite's ephemeris information, or the target base station's information.

6. The method according to claim 1, further comprising: Receiving, from the satellite, at least one of an indicator indicating execution of a CSI measurement process and a CSI reporting process or an indicator indicating non-execution of a CSI measurement process and a CSI reporting process.

7. The method according to claim 1, wherein Receiving a handover command message from the satellite includes: receiving, from the satellite, information that the satellite typically sends to the group through a unicast, multicast, or broadcast scheme.

8. A method for a satellite, comprising: Configuring a group for a user equipment (UE) served by the satellite, based on a beam region supported by the satellite; Sending a group indicator for the group to the UE; Selecting at least one UE from among the UEs to perform a channel state information (CSI) measurement process and a CSI reporting process; Receiving, from at least one UE, a message including the CSI of the group; Sending a handover request message for a handover determined based on the CSI to a target satellite; Receiving a handover request confirmation message from the target satellite, where the handover request confirmation message indicates that the handover request according to the handover request message is approved; And In response to the satellite's handover request being approved by the target satellite, sending a handover command message to the UEs belonging to the group.

9. The method according to claim 8, wherein Configuring a group for the UE served by the satellite includes: configuring a group for the UE based on at least one of a beam region, a cell remaining time, or beam region determination information, where the cell remaining time is the time for which the UE is in a state served by the beam region, and where the beam region determination information includes at least one of the UE's location information, the satellite's ephemeris information, or the target satellite's information.

10. The method according to claim 8, wherein, Selecting at least one UE to perform a CSI measurement process and a CSI reporting process includes: selecting, from among the UEs, UEs whose cell remaining time falls within a time range configured by the satellite as at least one UE to perform a CSI measurement process and a CSI reporting process, where the cell remaining time is the time for which the UE is in a state served by the beam region.

11. The method according to claim 8, wherein, Sending a handover command message to the UEs belonging to the group includes: sending, to the UEs, information that is typically sent to the group through a unicast, multicast, or broadcast scheme.

12. A user equipment (UE) comprising at least one processor, wherein, The at least one processor causes the UE to perform: Receive group configuration information for a group including a UE from a satellite based on a satellite-supported beam region; Receive a group indicator indicating the group from the satellite; Measure channel state information (CSI) of the group; Report a message including CSI to the satellite; and Receive a handover command message for handover determined based on the result of measuring CSI from the satellite.

13. The UE according to claim 12, wherein, The group configuration information includes at least one group identifier (ID) based on the beam region.

14. The UE according to claim 12, wherein, When the cell remaining time falls within a time range configured by the satellite, the group configuration information includes a group ID for identifying a group including the UE having the cell remaining time, where the cell remaining time is the time when the UE is in a state served by the beam region.

15. The UE according to claim 12, wherein, The at least one processor causes the UE to perform: Determine the beam region that occupies the largest part of the tracking area in the satellite-supported beam region as the beam region related to the tracking area.

16. The UE according to claim 12, wherein, The at least one processor causes the UE to perform: Determine the beam region supporting the UE based on beam region determination information, where the beam region determination information includes at least one of the UE's location information, the satellite's ephemeris information, or the target base station's information.

17. The UE according to claim 12, wherein, The at least one processor causes the UE to perform: Receive from the satellite at least one of an indicator indicating to perform a CSI measurement process and a CSI reporting process or an indicator indicating not to perform a CSI measurement process and a CSI reporting process.

18. The UE according to claim 12, wherein, When receiving a handover command message from the satellite, the at least one processor causes the UE to perform: Receive from the satellite information that the satellite typically sends to the group via a unicast, multicast, or broadcast scheme.

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