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

Abstract

A method and apparatus for group handover signaling in a non-terrestrial network are disclosed. A method of a user equipment (UE) may comprise the steps of: receiving common signaling configuration information on a UE group from a satellite; reporting a channel state information (CSI) report message including the CSI to the satellite; receiving a handover command message from the satellite through common signaling for the UE group; determining whether the common signaling configuration information has changed based on the handover command message; and transmitting a handover completion message to the satellite through the common signaling for the UE group if the common signaling configuration information on the UE group is not changed.

Description

Technical Field

[0001] The present invention relates to group handover technology in a non-terrestrial network, and more specifically, to signaling technology in the group handover process. 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 frequency bands of 6 GHz or below, but also frequency bands of 6 GHz or above. That is, a 5G communication network can support frequency range FR1 band and / or FR2 band. 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, technologies 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 function 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 TN environment, a cell that supports the data services of a terminal may have a relatively small coverage area. Accordingly, the number of terminals served by a single cell may be small. When served by a fixed base station, handover may occur due to the movement of the terminal. Therefore, when served by a fixed base station, handovers may not occur simultaneously but may occur individually. When a handover occurs in a TN environment, configuration information for the terminal requesting the handover may be generated at the target cell. The configuration information may be sent from the source cell to the terminal. Alternatively, the current configuration information of the terminal requesting the handover may be sent by the terminal to the target cell. The target cell may change the configuration information received from the terminal. The target cell may send only the changed portion of the configuration information to the terminal via the source cell through a handover request confirmation message and / or a handover command message.

[0006] In contrast, in an NTN environment, a cell that supports a terminal may have a relatively large coverage area, and the number of served terminals may be large. Additionally, handovers that occur in an NTN environment may be caused by the movement of a satellite. Accordingly, handovers that occur in an NTN environment may occur simultaneously or at similar times for a large number of terminals. Therefore, if handover signaling is performed individually for each terminal as in a conventional TN environment, a very large handover signaling overhead may occur. This may lead to an increase in network load and resource consumption. Summary of the Invention

[0007] Technical Problem

[0008] The present invention is directed to providing a method and apparatus for group handover signaling 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, common signaling configuration information for a UE group; reporting a CSI report message including channel state information (CSI) to the satellite; receiving, from the satellite through common signaling for the UE group to which the UE belongs, a handover command message for a handover determined based on the CSI; determining whether the common signaling configuration information for the UE has changed based on the handover command message; and in response to the common signaling configuration information for the UE group to which the UE belongs not having changed, sending a handover completion message to the satellite through common signaling for the UE group to which the UE belongs.

[0011] The method may further include: in response to the common signaling configuration information having changed, sending a handover completion message to the satellite through individual signaling for the UE based on first signaling configuration information received by the UE, where the common signaling is the same signaling for each UE of the UE group, and the individual signaling is independent signaling for each UE of the UE group.

[0012] Determining whether the common signaling configuration information for a UE has changed may include: comparing the common signaling configuration information configured in the UE with the first signaling configuration information included in a handover command message to determine whether the common signaling configuration information has changed.

[0013] The handover command message may include a field indicating whether the common signaling configuration information has changed. The field set to a first value may indicate that the common signaling configuration information has changed, and the field set to a second value may indicate that the common signaling configuration information has not changed.

[0014] Determining whether the common signaling configuration information for a UE has changed may include: in response to receiving RRC configuration change information including first signaling configuration information sent by a satellite, determining that the common signaling configuration information for the UE has changed.

[0015] Determining whether the common signaling configuration information for a UE has changed may include: in response to not receiving a handover command message from a satellite within a first time period, determining that the common signaling configuration information for the UE has not changed.

[0016] Determining whether the common signaling configuration information for a UE has changed may include: in response to not receiving RRC configuration change information from a satellite within a second time period, determining that the common signaling configuration information for the UE has not changed.

[0017] The handover command message may include at least one of an identifier (ID) of a UE for which the common signaling configuration information has not changed, an ID of a UE for which the common signaling configuration information has changed, or the first signaling configuration information.

[0018] A method for a serving base station for achieving the above object according to a second exemplary embodiment of the present invention may include: configuring a user equipment (UE) group; sending common signaling configuration information for the UE group to the UE; receiving a CSI measurement report message including channel state information (CSI) measured by the UE from the UE; in response to a target base station approving a handover for the UE based on the CSI, sending a handover command message to the UE through the common signaling for the UE group to which the UE belongs; and receiving a handover completion message from the UE through the common signaling for the UE group to which the UE belongs.

[0019] The method may further include: sending RRC configuration change information including first signaling configuration information to the UE, wherein when the first signaling configuration information is sent, a handover completion message is received through a separate signaling instead of through the common signaling, the common signaling being the same signaling for each UE of the UE group, and the separate signaling being an independent signaling for each UE of the UE group.

[0020] The method may further include: sending a handover request message including CSI and common signaling configuration information to a target base station; receiving a handover request confirmation message including first signaling configuration information from the target base station.

[0021] The handover request confirmation message may include at least one of an identifier (ID) of a UE for which the common signaling configuration information has not changed, an ID of a UE for which the common signaling configuration information has changed, or the first signaling configuration information.

[0022] A user equipment (UE) according to a third exemplary embodiment for achieving the above object according to the present invention may include: at least one processor, wherein the at least one processor may cause the UE to perform: receiving common signaling configuration information for a UE group from a satellite; reporting a CSI report message including channel state information (CSI) to the satellite; receiving a handover command message for a handover determined based on the CSI from the satellite via common signaling for the UE group to which the UE belongs; determining whether the common signaling configuration information for the UE has changed based on the handover command message; and in response to the common signaling configuration information for the UE group to which the UE belongs not having changed, sending a handover completion message to the satellite via common signaling for the UE group to which the UE belongs.

[0023] The at least one processor may cause the UE to perform: in response to the common signaling configuration information having changed, sending a handover completion message to the satellite via individual signaling for the UE based on the first signaling configuration information received by the UE, wherein the common signaling is the same signaling for each UE of the UE group, and the individual signaling is independent signaling for each UE of the UE group.

[0024] When determining whether the common signaling configuration information for the UE has changed, the at least one processor may cause the UE to perform: comparing the common signaling configuration information configured in the UE with the first signaling configuration information included in the handover command message to determine whether the common signaling configuration information has changed.

[0025] The handover command message may include a field indicating whether the common signaling configuration information has changed, a field set to a first value may indicate that the common signaling configuration information has changed, and a field set to a second value may indicate that the common signaling configuration information has not changed.

[0026] When determining whether the common signaling configuration information for the UE has changed, the at least one processor may cause the UE to perform: in response to receiving RRC configuration change information including the first signaling configuration information sent by the satellite, determining that the common signaling configuration information for the UE has changed.

[0027] When determining whether the common signaling configuration information for the UE has changed, the at least one processor may cause the UE to perform: determining that the common signaling configuration information for the UE has not changed in response to not receiving a handover command message from the satellite within a first time period.

[0028] When determining whether the common signaling configuration information for the UE has changed, the at least one processor may cause the UE to perform: determining that the common signaling configuration information for the UE has not changed in response to not receiving RRC configuration change information from the satellite within a second time period.

[0029] The handover command message may include at least one of an identifier (ID) of a UE for which the common signaling configuration information has not changed, an ID of a UE for which the common signaling configuration information has changed, or first signaling configuration information.

[0030] Advantageous Effects

[0031] According to the present invention, group handover signaling in a non-terrestrial network can reduce the load generated during the process of handling handover signaling. Additionally, group-based handover signaling can reduce the resources consumed during the signaling process. Brief Description of the Drawings

[0032] Figure 1a is a conceptual diagram showing a first exemplary embodiment of a non-terrestrial network.

[0033] Figure 1b is a conceptual diagram showing a second exemplary embodiment of a non-terrestrial network.

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

[0035] Figure 2b is a conceptual diagram showing a fourth exemplary embodiment of a non-terrestrial network.

[0036] Figure 2c is a conceptual diagram showing a fifth exemplary embodiment of a non-terrestrial network.

[0037] Figure 3 is a block diagram showing a first exemplary embodiment of a communication node constituting a non-terrestrial network.

[0038] Figure 4 is a block diagram showing a first exemplary embodiment of a communication node performing communication.

[0039] Figure 5a is a block diagram showing a first exemplary embodiment of a transmission path.

[0040] Figure 5b is a block diagram showing a first exemplary embodiment of a reception path.

[0041] Figure 6a It 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.

[0042] Figure 6b It 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.

[0043] Figure 7a It is a conceptual diagram showing a first exemplary implementation of the user plane protocol stack in a non-terrestrial network based on a regenerated payload.

[0044] Figure 7b It is a conceptual diagram showing a first exemplary implementation of the control plane protocol stack in a non-terrestrial network based on a regenerated payload.

[0045] Figure 8a It is a conceptual diagram showing a first exemplary implementation of handover in a non-terrestrial network.

[0046] Figure 8b It is a conceptual diagram showing a second exemplary implementation of handover in a non-terrestrial network.

[0047] Figure 9a It is a conceptual diagram showing a first exemplary implementation of the handover process.

[0048] Figure 9b It is a conceptual diagram showing a second exemplary implementation of the handover process.

[0049] Figure 10 It is a conceptual diagram showing a third exemplary implementation of the handover process.

[0050] Figure 11 It is a sequence diagram showing a first exemplary implementation of a signaling method in a non-terrestrial network.

[0051] Figure 12a It is a flowchart showing a first exemplary implementation of a signaling configuration method.

[0052] Figure 12b It is a flowchart showing a second exemplary implementation of a signaling configuration method.

[0053] Figure 12c It is a flowchart showing a third exemplary implementation of a signaling configuration method.

[0054] Figure 12d It is a flowchart showing a fourth exemplary implementation of a signaling configuration method. Detailed implementation

[0055] 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.

[0056] 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.

[0057] 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 an exemplary embodiment 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".

[0058] 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".

[0059] It will be understood that when an element is referred to as being "connected" or "coupled" to another element, it may be directly connected or coupled to the other element, or there may be intervening elements. In contrast, when an element is referred to as being "directly connected" or "directly coupled" to another element, there are no intervening elements.

[0060] 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.

[0061] 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 that is 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.

[0062] Hereinafter, exemplary embodiments of the present invention will be described in more detail with reference to the accompanying drawings. To facilitate an overall understanding of the present invention in the description, 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 may 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.

[0063] 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.

[0064] A base station may refer to a Node B, an evolved Node B (eNodeB), a next-generation node B (gNodeB), a gNB, a device, an apparatus, a node, a communication node, a base transceiver station (BTS), a radio remote head (RRH), a transmission reception point (TRP), a radio unit (RU), a roadside unit (RSU), a radio transceiver, an access point, an access node, etc. A UE may refer to a terminal, a device, an apparatus, a node, a communication node, an end node, an access terminal, a mobile terminal, a station, a subscriber station, a mobile station, a portable subscriber station, an on-broad unit (OBU), etc.

[0065] 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 (CE). 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)).

[0066] 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".

[0067] 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 communication technology among LTE communication technology, 5G communication technology, or 6G communication technology. The non-terrestrial network may provide communication services in various frequency bands.

[0068] 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.

[0069] Figure 1a It is a conceptual diagram showing a first exemplary embodiment of a non-terrestrial network.

[0070] 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 a LEO satellite and / or a MEO satellite.

[0071] 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.

[0072] In the non-terrestrial network, the following three types of service links may be supported.

[0073] - 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).

[0074] - 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).

[0075] - 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 or non - steerable beam).

[0076] The communication node 120 can perform communication with the satellite 110 (e.g., downlink communication and uplink communication) using 4G communication technology, 5G communication technology, and / or 6G communication technology. The communication between the satellite 110 and the communication node 120 can be performed using the NR - Uu interface and / or 6G - Uu interface. When dual connectivity (DC) is supported, the communication node 120 can be connected to other base stations (e.g., base stations supporting 4G, 5G, and / or 6G functions) as well as the satellite 110, and perform DC operations based on the technologies defined in the 4G, 5G, and / or 6G technical specifications.

[0077] The gateway 130 can be located at a ground location, and a feeder link can be established between the satellite 110 and the gateway 130. The feeder link can be a radio link. The gateway 130 can be referred to as a "non - terrestrial network (NTN) gateway". The communication between the satellite 110 and the gateway 130 can be performed based on the NR - Uu interface, 6G - Uu interface, or satellite radio interface (SRI). The gateway 130 can be connected to the data network 140. There can be a "core network" between the gateway 130 and the data network 140. In this case, the gateway 130 can be connected to the core network, and the core network can be connected to the 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. The communication between the gateway 130 and the core network can be performed based on the NG - C / U interface or 6G - C / U interface.

[0078] As Figure 1b shown in the exemplary embodiment of, in the NTN based on a transparent payload, there can be a "core network" between the gateway 130 and the data network 140.

[0079] Figure 1b is a conceptual diagram showing a second exemplary embodiment of a non - terrestrial network.

[0080] As Figure 1b 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.

[0081] Figure 2a It is a conceptual diagram showing a third exemplary embodiment of a non-terrestrial network.

[0082] 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.

[0083] 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.

[0084] The communication node 220 can perform communication with the satellite 211 (e.g., downlink communication or uplink communication) 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.

[0085] The gateway 230 can be located at a ground location. 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.

[0086] As Figure 2b and Figure 2c shown in the exemplary embodiments, there can be a "core network" between the gateway 230 and the data network 240.

[0087] 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.

[0088] 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, it may not be possible to establish an ISL between satellites, while in Figure 2c the non-terrestrial network, an ISL between satellites can be established.

[0089] On the other hand, constituting Figure 1a , Figure 1b ,Figure 2a , Figure 2b and / or Figure 2c Entities of the non-terrestrial network (e.g., satellites, base stations, UEs, communication nodes, gateways, etc.) as shown can be configured as follows. In the present invention, the entity can be referred to as a communication node.

[0090] Figure 3 is a block diagram showing a first exemplary embodiment of a communication node constituting a non-terrestrial network.

[0091] As Figure 3 shown, the communication node 300 can 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 can further include an input interface device 340, an output interface device 350, a storage device 360, etc. Components included in the communication node 300 can be connected via a bus 370 to communicate with each other.

[0092] However, each component included in the communication node 300 can 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 can 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.

[0093] The processor 310 can execute at least one instruction stored in at least one of the memory 320 and the storage device 360. The processor 310 can 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 can be configured as at least one of a volatile storage medium and a non-volatile storage medium. For example, the memory 320 can be configured with at least one of a read-only memory (ROM) and a random access memory (RAM).

[0094] On the other hand, a communication node performing communication in a communication network (e.g., a non-terrestrial network) can be configured as follows. Figure 4 The communication node as shown can be Figure 3 a specific exemplary embodiment of the communication node as shown.

[0095] Figure 4 is a block diagram showing a first exemplary embodiment of a communication node performing communication.

[0096] As Figure 4As shown, each of the first communication node 400a and the second communication node 400b can be a base station or a UE. The first communication node 400a can send a signal to the second communication node 400b. A transmission processor 411 included in the first communication node 400a can receive data (e.g., data units) from a data source 410. The transmission processor 411 can receive control information from a controller 416. The control information can 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).

[0097] The transmission processor 411 can generate data symbols by performing processing operations on the data (e.g., encoding operations, symbol mapping operations, etc.). The transmission processor 411 can generate control symbols by performing processing operations on the control information (e.g., encoding operations, symbol mapping operations, etc.). Additionally, the transmission processor 411 can generate synchronization / reference symbols for synchronization signals and / or reference signals.

[0098] The Tx MIMO processor 412 can 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) can be provided to modulators (MOD) included in transceivers 413a to 413t. The modulators can generate modulated symbols by performing processing operations on the symbol stream, and can 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 transceivers 413a to 413t can be transmitted via antennas 414a to 414t.

[0099] The signals transmitted by the first communication node 400a can be received at antennas 464a to 464r of the second communication node 400b. The signals received at antennas 464a to 464r can be provided to demodulators (DEMOD) included in transceivers 463a to 463r. The demodulators (DEMOD) can obtain samples by performing processing operations on the signals (e.g., filtering operations, amplification operations, downconversion operations, digital conversion operations, etc.). The demodulators can perform additional processing operations on the samples to obtain symbols. The MIMO detector 462 can perform MIMO detection operations on the symbols. The reception processor 461 can perform processing operations on the symbols (e.g., deinterleaving operations, decoding operations, etc.). The output of the reception processor 461 can be provided to a data sink 460 and a controller 466. For example, the data can be provided to the data sink 460, and the control information can be provided to the controller 466.

[0100] On the other hand, the second communication node 400b can send a signal to the first communication node 400a. A transmission processor 468 included in the second communication node 400b can receive data (e.g., data units) from a data source 467, and perform processing operations on the data to generate data symbols. The transmission processor 468 can receive control information from a controller 466, and perform processing operations on the control information to generate control symbols. In addition, the transmission processor 468 can generate reference symbols by performing processing operations on reference signals.

[0101] The Tx MIMO processor 469 can perform spatial processing operations (e.g., precoding operations) on the data symbols, control symbols, and / or reference symbols. The output of the Tx MIMO processor 469 (e.g., symbol stream) can be provided to modulators (MOD) included in transceivers 463a to 463t. The modulators can generate modulated symbols by performing processing operations on the symbol stream, and can 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 transceivers 463a to 463t can be transmitted through antennas 464a to 464t.

[0102] The signal transmitted by the second communication node 400b can be received at antennas 414a to 414r of the first communication node 400a. The signal received at antennas 414a to 414r can be provided to demodulators (DEMOD) included in transceivers 413a to 413r. The demodulators can obtain samples by performing processing operations on the signal (e.g., filtering operations, amplification operations, downconversion operations, digital conversion operations, etc.). The demodulators can perform additional processing operations on the samples to obtain symbols. The MIMO detector 420 can perform MIMO detection operations on the symbols. The reception processor 419 can perform processing operations on the symbols (e.g., deinterleaving operations, decoding operations, etc.). The output of the reception processor 419 can be provided to the data sink 418 and the controller 416. For example, data can be provided to the data sink 418, and control information can be provided to the controller 416.

[0103] The memories 415 and 465 can store data, control information, and / or program codes. The scheduler 417 can perform scheduling operations for communication. Figure 4 The illustrated processors 411, 412, 419, 461, 468, and 469 and the controllers 416 and 466 can be Figure 3The processor 310 shown, and can be used to execute the methods described in the present invention.

[0104] 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.

[0105] As Figure 5a and Figure 5b shown, the transmission path 510 can be implemented in a communication node that transmits signals, and the reception path 520 can be implemented in a communication node that receives signals. The transmission path 510 may 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 reception path 520 may 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 may be a natural number.

[0106] In the transmission path 510, information bits may be input to the channel coding and modulation block 511. The channel coding and modulation block 511 may perform an encoding operation on the information bits (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.). The output of the channel coding and modulation block 511 may be a sequence of modulated symbols.

[0107] The S-to-P block 512 may convert the frequency-domain modulated symbols into a parallel symbol stream to generate N parallel symbol streams. N may be the IFFT size or the FFT size. The N-point IFFT block 513 may generate a time-domain signal by performing an IFFT operation on the N parallel symbol streams. The P-to-S block 514 may convert the output of the N-point IFFT block 513 (e.g., a parallel signal) into a serial signal to generate a serial signal.

[0108] The CP addition block 515 can insert CP into the signal. The UC 516 can up-convert the frequency of the output of the CP addition block 515 to the radio frequency (RF) frequency. In addition, the output of the CP addition block 515 can be filtered in the baseband before up-conversion.

[0109] 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 the reverse operations of those in the transmission path 510. The DC 521 can down-convert the frequency of the received signal to the baseband frequency. The CP deletion block 522 can delete the CP from the signal. The output of the CP deletion 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.

[0110] In Figure 5a and Figure 5b the discrete Fourier transform (DFT) and the inverse DFT (IDFT) can be used to replace the FFT and the 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

[0111] On the other hand, the NTN reference scenario can be defined as shown in Table 1 below.

[0112] [Table 1]

[0113] 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

[0114] 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 2cWhen the satellites 211 and 212 in the NTN shown are GEO satellites (e.g., GEO supporting the regeneration function), this can be referred to as "Scenario B".

[0115] When Figure 1a and / or Figure 1b 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".

[0116] The parameters for the NTN reference scenarios defined in Table 1 can be defined as shown in Table 2 below.

[0117] [Table 2]

[0118]

[0119] In addition, in the scenarios defined in Table 1, the delay constraints can be defined as shown in Table 3 below.

[0120] [Table 3]

[0121]

[0122] 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.

[0123] 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 to a 6G communication network. Figure 6bThe protocol stack of the control plane shown can be applied in the same or similar manner to a 6G communication network.

[0124] Figure 7a FIG. 4 is a conceptual diagram showing a first exemplary embodiment of the protocol stack of the user plane in a non-terrestrial network based on regenerated payloads. Figure 7b FIG. 6 is a conceptual diagram showing a first exemplary embodiment of the protocol stack of the control plane in a non-terrestrial network based on regenerated payloads.

[0125] 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., the 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.

[0126] 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.

[0127] [Table 4]

[0128]

[0129]

[0130] The NTN-Config defined in Table 4 can include the information elements defined in Table 5 below.

[0131] [Table 5]

[0132]

[0133] The EphemerisInfo defined in Table 5 can include the information elements defined in Table 6 below.

[0134] [Table 6]

[0135]

[0136]

[0137] On the other hand, when the terminals requesting handover operate in a group-based manner in the NTN environment, the signaling overhead for handover can be reduced. Additionally, the terminals requesting handover can send their current configuration information to the target cell, and the target cell can directly apply the current configuration information. Furthermore, if the target cell cannot apply the current configuration information, the target cell can modify the configuration information for the terminals for which the configuration information cannot be applied. Through group-based handover signaling, the satellite and the terminals can reduce the signaling load for handover. In this case, the satellite and the terminals can distinguish between the terminals configured with the same configuration information and the terminals configured with changed signaling configuration information, and perform signaling accordingly. Additionally, the terminals configured with the same configuration information can use multicast signaling to reduce the resource consumption caused by signaling. Therefore, the present invention proposes a separate handover signaling method for the terminals configured with the same configuration information and the terminals configured with changed signaling configuration information.

[0138] Figure 8a is a conceptual diagram showing a first exemplary embodiment of handover in a non-terrestrial network.

[0139] As Figure 8a shown, during an intra-SAT handover process, both the serving link and / or the feeder link can be changed.

[0140] Figure 8b is a conceptual diagram showing a second exemplary embodiment of handover in a non-terrestrial network.

[0141] As Figure 8b shown, during an inter-SAT handover process, the serving link can remain unchanged while the feeder link can be changed.

[0142] On the other hand, in an NTN satellite system, due to the change in the beam coverage area on the ground caused by the movement of the satellite, there may be an earth-fixed beam (EFB) or an earth-moving beam (EMB) environment. Applying the same grouping method to both scenarios may not be efficient, and it may be difficult to achieve the effect of reducing handover signaling through grouping. Therefore, the present invention proposes a grouping method suitable for each scenario.

[0143] Figure 9a is a conceptual diagram showing a first exemplary embodiment of the handover process.

[0144] As Figure 9aAs shown, in an EFB environment, satellites (i.e., the first satellite, the second satellite) can form cell coverage. In this case, beam coverage can be formed by at least one beam area (e.g., a beam point). A beam area can refer to the area covered by one beam. In other words, a satellite can form one or more beam areas (beam points).

[0145] In an EFB environment, all terminals located in the same beam area can request a handover process to the satellite at the same or similar time. When terminals are included in the same beam area, 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 area as the same group.

[0146] Figure 9b It is a conceptual diagram showing a second exemplary embodiment of the handover process.

[0147] As Figure 9a and Figure 9b shown, in an EFB-based non-terrestrial network (hereinafter referred to as "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 at the same satellite through beam switching. For example, in the intra-SAT handover process, all terminals connected to the first cell of the first satellite can be switched to the second cell of the first satellite. In this case, all terminals can be switched to the second cell at the same or similar time. EFB can be supported through beam steering within the same satellite.

[0148] In the inter-SAT handover process, a terminal can perform a handover process between satellites. In the inter-SAT handover process, all terminals connected to the first cell of the first satellite can be switched to the second cell of the second satellite. In this case, all terminals can be switched 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 an inter-SAT handover process. EFB can be supported through a new cell of a new satellite (e.g., the second satellite).

[0149] Due to the high altitude in non-terrestrial networks, the handover process based on reference signal received power (RSRP) may not be effective. Therefore, a handover process suitable for non-terrestrial networks may be required. Even when the satellite in the EFB environment moves 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 terminals within the same cell (e.g., all terminals or some terminals). An efficient handover process that takes into account the characteristics of the above EFB non-terrestrial network may be required.

[0150] Figure 10 is a conceptual diagram showing a third exemplary embodiment of the handover process.

[0151] As Figure 10 shown, in the EMB environment, terminals included in the same beam area may have different remaining cell times according to the positions of the terminals. When the remaining cell times of the respective terminals are different, the times at which each terminal requests a handover may be different. For example, the first terminal 1021, the second terminal 1022, and the third terminal 1023 may be included in one beam area (e.g., beam area 12). The remaining cell time of the first terminal 1021 may be the longest compared to other terminals. In this case, the terminals belonging to the same beam area may perform handovers in ascending order of the remaining cell time values.

[0152] On the other hand, regardless of the remaining cell time, the target satellite of the terminal may change according to the position of the terminal. For example, the third terminal may be included in beam area 12, but may also be included in beam area 14. The second terminal may be included in beam areas 12, 13, and 15. Therefore, the third terminal may perform a handover process to the target satellite supporting beam area 14. The second terminal may perform a handover process to the target satellite supporting beam area 15.

[0153] The satellite can configure a group for the terminal based on the remaining cell time value and the beam area determination information, so that the terminals within the same beam area can perform the handover process through common signaling. The beam area determination information may refer to information used to determine one beam area supporting the terminal when the terminal is included in multiple beam areas. The beam area determination information may 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 may 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.

[0154] Figure 11 It is a sequence diagram showing a first exemplary embodiment of a signaling method in a non-terrestrial network.

[0155] As Figure 11 shown, handovers occurring in the NTN environment may be caused by the movement of satellites. Accordingly, handovers occurring in the NTN environment may occur simultaneously or at similar times for a large number of terminals. Therefore, if handover signaling is performed individually for each terminal as in a conventional TN environment, a very large handover signaling overhead may occur. This may lead to an increase in network load and resource consumption.

[0156] To solve this problem, the satellite may perform group configuration for the terminals. Accordingly, the present invention proposes a group-based signaling method for terminals belonging to a group. Group-based signaling may be a method of using common signaling. In other words, group-based signaling may be a method of sending a message in a multicast scheme. However, group-based signaling may not be limited to a method of sending a message in a multicast scheme. For example, group-based signaling may be a method of sending a message in a unicast or broadcast scheme.

[0157] The first base station may be referred to as a serving base station. The first base station may form a serving cell for the terminals. The first base station may send group-based common signaling configuration information to the first satellite (S1110). The first satellite may receive the group-based common signaling configuration information sent by the first base station. The group-based common signaling configuration information may include configuration information that is applied identically (e.g., commonly) to a group of terminals (UE group). Additionally, the group-based common signaling configuration information may include configuration information for the terminals to perform CSI-related operations. For example, the configuration information for performing CSI-related operations may include at least one of CSI measurement time, CSI measurement period, CSI report time, CSI report period, or information about the terminals performing CSI measurement. The UE group may include one or more UEs. The UE group may be configured by the first base station and / or the first satellite.

[0158] The first satellite may send the group-based common signaling configuration information sent by the first base station to the terminals within the group. The terminals may receive the group-based common signaling configuration information sent by the first satellite. For example, the first satellite may send the group-based common signaling configuration information to the Nth terminal. The Nth terminal may receive the group-based common signaling configuration information sent by the first satellite.

[0159] The terminals within the group can perform the CSI measurement process by using the configuration information for performing CSI-related operations included in the group-based common signaling configuration information. The terminals within the group can send a CSI report message to the first satellite by using the common signaling configuration information for the terminal group sent by the first satellite (S1120). In other words, the terminals within the group can send a CSI report message to the first satellite through the common signaling for the terminal group (S1120). The CSI report message can include at least one of a CSI measurement value, a CSI report value, timing information, the location of the terminal, or ephemeris information of the satellite. The first satellite can receive the CSI report message sent by the terminals within the group. The first satellite can send the CSI report message received from the terminals within the group to the first base station. The first base station can receive the CSI report message sent by the first satellite.

[0160] The first base station can determine to initiate a handover based on the information included in the CSI report message (S1130). In other words, the first base station can use at least one of the CSI measurement value and report value, timing information, terminal location, or satellite ephemeris information to determine to initiate a handover.

[0161] When the first base station determines to initiate a handover, the first base station can send a handover request message to the second base station (S1140). The second base station can refer to the base station that supports the target cell. The handover request message can include the information required for the second base station to prepare for the handover. Additionally, the handover request message can include information about the terminals within the group (terminal ID) or the current signaling configuration information of the terminals. The signaling configuration information of the terminals can include the signaling information for the terminals. The signaling information can refer to the common signaling information for the terminals within the group. The common signaling can refer to the same signaling for the terminals within the group. The signaling information for the terminals can include the IDs of the terminals that receive data through the same signaling. The second base station can receive the handover request message sent by the first base station.

[0162] The second base station can use the handover request message sent by the first base station to determine whether to accept the handover for the terminals. In other words, when receiving the handover request message, the second base station can perform admission control to determine whether to accept the handover for the terminals.

[0163] When the second base station determines to accept the handover for the terminal, the second base station may prepare for the handover for the terminal. The second base station may send a handover request confirmation message to the first base station, and the handover request confirmation message is a confirmation message for the handover request message. In addition, when the second base station accepts the handover for the terminal, the second base station may use the handover request message sent by the first base station to generate the terminal ID or the first signaling configuration information. The ID of the terminal may include at least one of the ID of the terminal with the unchanged common signaling configuration information or the ID of the terminal with the changed common signaling configuration information. The first signaling configuration information may refer to the changed common signaling configuration information. In other words, the first signaling configuration information may refer to the information about the change of the common signaling configuration information. The second base station may generate a handover request confirmation message including the information about the terminal ID and the changed signaling configuration information. The second base station may send the handover request confirmation message to the first base station (S1150). The handover request confirmation message may include at least one of the information about the terminal ID or the first signaling configuration information. The first base station may receive the handover request confirmation message sent by the second base station. In addition, the handover request confirmation message may include the information about the random access resources used in the access process for the terminal to access the target base station. When the first base station receives the handover request confirmation message from the second base station, the first base station may determine that the handover process has been initiated. The first base station may send a handover command message to the first satellite (S1160). The handover command message may include the handover request confirmation message. The first satellite may receive the handover command message sent by the first base station. The first satellite may send the handover command message to the terminals within the group. The terminals within the group may receive the handover command message sent by the first satellite. In other words, the first satellite may send the handover command message to all the terminals within the group in a multicast scheme.

[0164] On the other hand, the handover command message sent by the first satellite in a multicast scheme may not include information. In other words, the handover command message may include a field indicating whether the common signaling configuration information has changed. The field indicating that the common signaling configuration information has changed (which is set to the first value) may indicate that the common signaling configuration information has changed. The field indicating that the common signaling configuration information has not changed (which is set to the second value) may indicate that the common signaling configuration information has not changed. The first value may indicate the information with a bit value of 1. The second value may indicate the information with a bit value of 0.

[0165] The terminals within the group can receive a handover command message sent by the first satellite in a multicast scheme. The terminals within the group can receive the handover command message within T1. T1 can refer to the system parameters of the satellite. T1 can indicate the time when the terminal can receive the handover command message. The terminals within the group can determine whether the common signaling configuration information has changed by using the handover command message. The method of using the handover command message to determine whether the group-based common signaling configuration information has changed can be as Figure 12d shown.

[0166] Figure 12d is a flowchart showing a fourth exemplary embodiment of a signaling configuration method.

[0167] As Figure 12d shown, the first satellite can send a handover command message to the terminals within the group in a multicast scheme. In this case, the handover command message can include at least one of the IDs of UEs for which the common signaling configuration information has not changed, or the IDs of UEs for which the common signaling configuration information has changed, or the first signaling configuration information.

[0168] The handover command message can include the following configurations.

[0169] [Table 7]

[0170]

[0171] In the "Same Configuration" field of Table 7, "0" can indicate that the common signaling configuration information has not changed. In the "Same Configuration" field of Table 7, "1" can indicate that the common signaling configuration information has changed.

[0172] The terminals within the group can determine whether they have received the handover command message sent by the first satellite (S1241). If the handover command message sent by the first satellite has not been received, the terminal can determine that the handover process has failed (S1242).

[0173] If the terminal receives the handover command message sent by the first satellite, the terminal can determine whether the common signaling configuration information is applied identically (S1243). In other words, the terminal can determine whether the common signaling configuration information for the terminal has changed. If the common signaling configuration information for the terminal has not changed, the terminal can determine that the common signaling configuration information for the terminal has not changed (S1247). If the common signaling configuration information for the terminal has changed, the terminal can determine that the common signaling configuration information for the terminal has changed (S1248).

[0174] On the other hand, when the common signaling configuration information has changed, the terminal can send a handover completion message to the satellite and / or the base station via individual signaling by using the first signaling configuration information.

[0175] Referring again to Figure 11 , the first satellite may send RRC configuration change information (RRCConfigChange) to a terminal (S1170) whose common signaling configuration information has changed. The RRC configuration change information may include first signaling configuration information. In other words, the RRC configuration change information (RRCConfigChange) may include changed signaling configuration information (e.g., UE-specific changed configuration information). On the other hand, terminals within a group may receive the RRC configuration change information from the first satellite in a multicast scheme. Terminals within a group may receive the RRC configuration change information within T2. T2 may refer to system parameters of the satellite. T2 may indicate the time at which a terminal may receive the RRC configuration change information.

[0176] Terminals within a group may determine whether the common signaling configuration information has changed by using at least one of a handover command message or the RRC configuration change information. A method for determining whether group-based common signaling configuration information has changed by using at least one of a handover command message or the RRC configuration change information may be as Figure 12a , Figure 12b and Figure 12c shown.

[0177] Figure 12a and 12c show methods for determining whether group-based common signaling configuration information has changed by using a handover command message and the RRC configuration change information. Figure 12b shows a method for determining whether group-based common signaling configuration information has changed by using the RRC configuration change information.

[0178] Figure 12a is a flowchart showing a first exemplary embodiment of a signaling configuration method.

[0179] As Figure 12a shown, a terminal within a group may determine whether it has received a handover command message sent by the first satellite (S1211). If the terminal has not received the handover command message sent by the first satellite, the terminal may determine that the handover process has failed (S1212).

[0180] If the terminal receives a handover command message sent by the first satellite, the terminal can determine whether it has received RRC configuration change information (S1216). If it has not received the RRC configuration change information sent by the first satellite, the terminal can determine that the configuration information for the terminal is the same as before (S1217). In other words, if it has not received the RRC configuration change information sent by the first satellite, the terminal can determine that the common signaling configuration information for the terminal has not changed. Additionally, the terminal can send and / or receive messages and / or information through the same signaling (common signaling) as before. For example, in FIG. 12, the first terminal and the Mth terminal can receive messages and / or information through the same signaling.

[0181] If the terminal has received the RRC configuration change information sent by the first satellite, the terminal can determine that part and / or all of the common signaling configuration information for the terminal has changed (S1218). In this case, the terminal can send and / or receive messages and / or information through a separate signaling using the changed signaling configuration information. For example, in FIG. 12, the Nth terminal can receive messages and / or information through the changed signaling (separate signaling).

[0182] The satellite and / or the base station can send a handover command message and / or RRC configuration change information for a group through common signaling with a time difference. In other words, in order to determine whether the common signaling configuration information has changed, the terminal can first receive the handover command message in a multicast scheme. The base station can send the RRC configuration change information after sending the handover command message.

[0183] Additionally, since the terminal determines whether the configuration has changed based on both the reception of the handover command message and the reception of the separate signaling, the reliability of signaling determination can be increased.

[0184] Figure 12b is a flowchart showing a second exemplary embodiment of a signaling configuration method.

[0185] As Figure 12b shown, the terminal can determine whether the common signaling configuration information has changed by only using the RRC configuration change information in the common signaling for the group.

[0186] The first satellite can refrain from sending a handover command message to the terminals within the group to reduce the signaling load. The first satellite can send the RRC configuration change information to the terminals within the group through common signaling.

[0187] The terminals within the group can determine whether they have received the RRC configuration change information sent by the first satellite (S1226). If they have not received the RRC configuration change information sent by the first satellite, the terminals can determine that the common signaling configuration information for the terminals is the same as before (S1227). If they have not received the RRC configuration change information within T2, the terminals can determine that the common signaling configuration information for the terminals is the same as before. In other words, the terminals can determine that the common signaling configuration information for the terminals has not changed.

[0188] If they have received the RRC configuration change information sent by the first satellite, the terminals can determine that part and / or all of the common signaling configuration information for the terminals has changed (S1228). The RRC configuration change information may include first signaling configuration information (changed common signaling configuration information). If they have received the RRC configuration change information within T2, the terminals can determine that the common signaling configuration information for the terminals has changed. Here, T2 can be pre-configured as a system parameter of the satellite.

[0189] On the other hand, the terminals can use the first signaling configuration information to send a handover completion message to the satellite and / or the base station via a separate signaling.

[0190] Figure 12c is a flowchart showing a third exemplary embodiment of a signaling configuration method.

[0191] As Figure 12c shown, the first satellite can send a handover command message to the terminals within the group. The first satellite and / or the first base station can add content to the handover command message. In other words, the handover command message may include a field indicating whether the common signaling configuration information has changed. The field indicating whether the common signaling configuration information has changed may include a first value or a second value. The first value may indicate that the common signaling configuration information has changed. The first value may be represented by the bit "1". The second value may indicate that the common signaling configuration information has not changed. The second value may be represented by the bit "0". In other words, the bit "1" may indicate that the common signaling configuration information for the terminals has changed. The bit "0" may indicate that the common signaling configuration information for the terminals has not changed.

[0192] The terminals within the group can determine whether they have received the handover command message sent by the first satellite (S1231). If they have not received the handover command message sent by the first satellite, the terminals can determine that the handover process has failed (S1232).

[0193] If the terminal receives a handover command message sent by the first satellite, the terminal may determine whether it has received the first signaling configuration information (S1233) included in the handover command message. In other words, the terminal may determine the value of the field indicating whether the common signaling configuration information has changed. If the information included in the handover command message is not the bit "1", the terminal may determine whether it has received RRC configuration change information (S1234). If the terminal has not received the RRC configuration change information sent by the first satellite, the terminal may determine that the common signaling configuration information for the terminal has not changed (S1237). If the terminal has received the RRC configuration change information sent by the first satellite, the terminal may determine that the handover process has failed (S1235).

[0194] If the information included in the handover command message is the bit "1", the terminal may determine whether it has received RRC configuration change information (S1236). If the terminal has not received the RRC configuration change information sent by the first satellite, the terminal may determine that the handover process has failed (S1239). If the terminal has received the RRC configuration change information sent by the first satellite, the terminal may determine that part and / or all of the common signaling configuration information for the terminal has changed (S1238). The RRC configuration change information may include the first signaling configuration information.

[0195] When determining the reception of the handover command message, the terminal may further determine whether it has received the handover command message within T1. When determining the reception of the RRC configuration change information, the terminal may further determine whether it has received the RRC configuration change information within T2.

[0196] If the common signaling configuration information for the terminal has not changed, the terminal may pre-execute the handover process using the bit information (i.e., bit "1" or bit "0") of the handover command message. Accordingly, the terminal may allocate the load of the handover process.

[0197] On the other hand, if the common signaling configuration information for the terminal has changed, the terminal may send and receive data with the satellite through separate signaling. In other words, if the common signaling configuration information has changed, the terminal may use the first signaling configuration information to send a handover completion message to the satellite and / or the base station through separate signaling. Different from the common signaling, the separate signaling may refer to the signaling sent separately between the satellite and the terminal. In other words, the separate signaling may refer to the signaling different from the signaling for the terminals within the group.

[0198] On the other hand, when a terminal included in a group receives a handover command message and / or RRC configuration change information, the terminal included in the group may perform an access procedure to a second satellite. In other words, the terminal may perform random access to the second satellite (target satellite) and may send a handover completion message to the second satellite. When sending the handover completion message to the second satellite, the terminal may send the handover completion message to the second satellite via common signaling or individual signaling. The second satellite may send the handover completion message sent by the terminal to a second base station. The second base station may refer to a target base station.

[0199] The operations of the method according to an exemplary embodiment of the present invention may be implemented as a computer-readable program or code in a computer-readable recording medium. The computer-readable recording medium may include all types of recording devices storing data readable by a computer system. In addition, the computer-readable recording medium may store and execute programs or codes that may be distributed in computer systems connected through a network and read by a computer in a distributed manner.

[0200] The computer-readable recording medium may include hardware devices specifically configured to store and execute program instructions, such as ROM, RAM, or flash memory. The program instructions may include not only machine language codes created by a compiler but also high-level language codes executable by a computer using an interpreter.

[0201] Although some aspects of the present invention have been described in the context of devices, these aspects may indicate corresponding descriptions according to the method, and a block or device may correspond to a step or a feature of a step of the method. Similarly, aspects described in the context of the method may be represented as features of the corresponding block or item or corresponding device. Some or all steps of the method may be performed by (or using) a hardware device 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 a device.

[0202] 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, the field-programmable gate array may be operated with a microprocessor to perform one of the methods described herein. Generally, the method is preferably performed by a specific hardware device.

[0203] 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 should not be regarded as departing from the spirit and scope of the present invention. Therefore, 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, common signaling configuration information for a UE group; Reporting, to the satellite, a CSI report message including channel state information (CSI); Receiving, from the satellite, a handover command message for a handover determined based on the CSI, via common signaling for the UE group to which the UE belongs; Determining whether the common signaling configuration information for the UE has changed, based on the handover command message; And In response to the common signaling configuration information for the UE group to which the UE belongs not having changed, sending, to the satellite, a handover completion message via the common signaling for the UE group to which the UE belongs.

2. The method according to claim 1, further comprising: In response to the common signaling configuration information having changed, sending, to the satellite, a handover completion message via dedicated signaling for the UE, based on the first signaling configuration information received by the UE, Wherein the common signaling is the same signaling for each UE in the UE group, and the dedicated signaling is independent signaling for each UE in the UE group.

3. The method according to claim 1, wherein Determining whether the common signaling configuration information for the UE has changed includes: comparing the common signaling configuration information configured in the UE with the first signaling configuration information included in the handover command message to determine whether the common signaling configuration information has changed.

4. The method according to claim 1, wherein The handover command message includes a field indicating whether the common signaling configuration information has changed, a field set to a first value indicating that the common signaling configuration information has changed, and a field set to a second value indicating that the common signaling configuration information has not changed.

5. The method according to claim 2, wherein Determining whether the common signaling configuration information for the UE has changed includes: determining that the common signaling configuration information for the UE has changed in response to receiving RRC configuration change information including the first signaling configuration information sent by the satellite.

6. The method according to claim 1, wherein, Determining whether the common signaling configuration information for the UE has changed includes: determining that the common signaling configuration information for the UE has not changed in response to not receiving a handover command message from the satellite within a first time period.

7. The method according to claim 1, wherein Determining whether the common signaling configuration information for the UE has changed includes: determining that the common signaling configuration information for the UE has not changed in response to not receiving RRC configuration change information from the satellite within a second time period.

8. The method according to claim 1, wherein, The handover command message includes at least one of an identifier (ID) of a UE for which the common signaling configuration information has not changed, an ID of a UE for which the common signaling configuration information has changed, or the first signaling configuration information.

9. A method for a serving base station, comprising: Configuring a user equipment (UE) group; Sending, to the UE, common signaling configuration information for the UE group; Receiving, from the UE, a CSI measurement report message including CSI measured by the UE; In response to a target base station approving a handover for the UE based on the CSI, sending, to the UE, a handover command message via the common signaling for the UE group to which the UE belongs; And Receiving, from the UE, a handover completion message via the common signaling for the UE group to which the UE belongs.

10. The method according to claim 9, further comprising: Send RRC configuration change information including first signaling configuration information to the UE, where when the first signaling configuration information is sent, the handover completion message is received via a dedicated signaling rather than a common signaling, the common signaling being the same signaling for each UE in the UE group, and the dedicated signaling being an independent signaling for each UE in the UE group.

11. The method according to claim 9, further comprising: Send a handover request message including CSI and common signaling configuration information to the target base station; And Receive a handover request confirmation message including first signaling configuration information from the target base station.

12. The method according to claim 9, wherein, The handover request confirmation message includes at least one of the identifier (ID) of the UE for which the common signaling configuration information has not changed, or the ID of the UE for which the common signaling configuration information has changed, or the first signaling configuration information.

13. A user equipment (UE), comprising: At least one processor, wherein the at least one processor causes the UE to perform: Receive common signaling configuration information for the UE group from the satellite; Report a CSI report message including channel state information (CSI) to the satellite; Receive a handover command message for handover determined based on the CSI from the satellite via the common signaling for the UE group to which the UE belongs; Determine whether the common signaling configuration information for the UE has changed based on the handover command message; and In response to the common signaling configuration information for the UE group to which the UE belongs not changing, send a handover completion message to the satellite via the common signaling for the UE group to which the UE belongs.

14. The UE according to claim 13, wherein, The at least one processor causes the UE to perform: in response to the common signaling configuration information having changed, send a handover completion message to the satellite via the dedicated signaling for the UE based on the first signaling configuration information received by the UE; wherein the common signaling is the same signaling for each UE in the UE group, and the dedicated signaling is an independent signaling for each UE in the UE group.

15. The UE according to claim 13, wherein, When determining whether the common signaling configuration information for the UE has changed, the at least one processor causes the UE to perform: compare the common signaling configuration information configured in the UE with the first signaling configuration information included in the handover command message to determine whether the common signaling configuration information has changed.

16. The UE according to claim 13, wherein, The handover command message includes a field indicating whether the common signaling configuration information has changed, a field set to a first value indicating that the common signaling configuration information has changed, and a field set to a second value indicating that the common signaling configuration information has not changed.

17. The UE according to claim 14, wherein, When determining whether the common signaling configuration information for the UE has changed, the at least one processor causes the UE to perform: in response to receiving RRC configuration change information including first signaling configuration information sent by the satellite, determine that the common signaling configuration information for the UE has changed.

18. The UE according to claim 13, wherein When determining whether the common signaling configuration information for the UE has changed, the at least one processor causes the UE to perform: in response to not receiving a handover command message from the satellite within a first time, determine that the common signaling configuration information for the UE has not changed.

19. The UE according to claim 13, wherein, When determining whether the common signaling configuration information for the UE has changed, the at least one processor causes the UE to perform: in response to not receiving RRC configuration change information from the satellite within a second time period, determining that the common signaling configuration information for the UE has not changed.

20. The UE according to claim 13, wherein The handover command message includes at least one of an identifier (ID) of a UE for which the common signaling configuration information has not changed, an ID of a UE for which the common signaling configuration information has changed, or first signaling configuration information.

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