Apparatus and method for acquiring system information of neighboring base station in wireless communication system

Abstract

The present disclosure relates to an operation method for a first base station in a wireless communication system, the method comprising the steps of: receiving a system information request message from a terminal; transmitting the system information request message to a second base station; receiving a system information message from the second base station; and transmitting the system information message to the terminal.

Description

Device and method for acquiring system information of a surrounding base station in a wireless communication system

[0001] The present disclosure relates to a wireless communication system, and in particular to an apparatus and method for acquiring system information (SI) between base stations in a wireless communication system.

[0002] With the advancement of mobile communication services, Non-Terrestrial Networks (NTNs), which are free from spatial constraints, are attracting attention, and low-orbit satellites, in particular, are expected to play a major role. Accordingly, 3GPP (3 rd The Generation Partnership Project is proceeding with standardization for non-terrestrial networks without spatial constraints to provide effective communication services.

[0003] The present disclosure is intended to provide an apparatus and method for effectively acquiring system information (SI) between base stations in a wireless communication system.

[0004] The present disclosure is intended to provide an apparatus and method for obtaining system information from another base station based on a request for system information from a terminal.

[0005] The present disclosure is intended to provide an apparatus and method for generating a system information message based on a list of system information, an identifier of a base station, types of System Information Blocks (SIBs), and original data of the SIBs.

[0006] The present disclosure is intended to provide an apparatus and method for transmitting system information messages according to reference times determined based on a predetermined timer.

[0007] The present disclosure is intended to provide an apparatus and method for determining reference times based on the time at which a terminal receives a system information message and a predetermined timer.

[0008] The present disclosure is intended to provide an apparatus and method for generating synchronized system information messages based on reference times.

[0009] According to one aspect of the present disclosure, a method of operation of a first base station in a wireless communication system is disclosed. The method may include the steps of receiving a System Information (SI) request message from a terminal, transmitting the System Information request message to a second base station, receiving a System Information message from the second base station, and transmitting the System Information message to the terminal.

[0010] According to another aspect of the present disclosure, a first base station is disclosed in a wireless communication system. The first base station comprises a transceiver and a processor connected to the transceiver, and the processor can control receiving a system information request message from a terminal, transmitting the system information request message to a second base station, receiving a system information message from the second base station, and transmitting the system information message to the terminal.

[0011] According to another aspect of the present disclosure, a method of operation of a second base station in a wireless communication system is disclosed. The method comprises the steps of receiving a system information request message from a first base station and transmitting a system information message to the first base station based on the system information request message, wherein the reception of the system information request message from the first base station may be based on a request for a system information message from the terminal.

[0012] According to another aspect of the present disclosure, a second base station is disclosed in a wireless communication system. The second base station includes a transceiver and a processor connected to the transceiver, wherein the processor receives a system information request message from a first base station and controls the transmission of a system information message to the first base station based on the system information request message, wherein the reception of the system information request message from the first base station may be based on a request for a system information message from the terminal.

[0013] According to another aspect of the present disclosure, a method of operation of a terminal in a wireless communication system is disclosed. The method comprises the steps of transmitting a system information request message to a first base station and receiving a system information message from the first base station, wherein the first base station may receive the system information message from a second base station based on the reception of the system information request message.

[0014] According to another aspect of the present disclosure, a terminal is disclosed in a wireless communication system. The terminal includes a transceiver and a processor connected to the transceiver, wherein the processor controls the transmission of a system information request message to a first base station and the reception of a system information message from the first base station, the first base station may receive the system information message from a second base station based on the reception of the system information request message.

[0015] According to embodiments of the present disclosure, system information between base stations in a wireless communication system can be effectively obtained.

[0016] FIG. 1 illustrates an example of a network according to one embodiment of the present disclosure.

[0017] FIG. 2 illustrates another example of a network according to one embodiment of the present disclosure.

[0018] FIG. 3 illustrates the configuration of a device in a wireless communication system according to one embodiment of the present disclosure.

[0019] FIG. 4 illustrates an example of a transparent satellite-based network according to one embodiment of the present disclosure.

[0020] FIG. 5 illustrates an example of a regenerative satellite-based network according to one embodiment of the present disclosure.

[0021] FIG. 6 illustrates an example of a procedure for obtaining system information according to one embodiment of the present disclosure.

[0022] FIG. 7 illustrates an example of a procedure for obtaining system information based on the interface of a first base station according to one embodiment of the present disclosure.

[0023] FIG. 8 illustrates an example of a procedure for obtaining synchronized system information based on a reference time according to one embodiment of the present disclosure.

[0024] FIG. 9 illustrates an example of a procedure in which a first base station acquires system information according to one embodiment of the present disclosure.

[0025] FIG. 10 illustrates an example of a procedure in which a first base station according to one embodiment of the present disclosure obtains synchronized system information based on a reference time.

[0026] FIG. 11 illustrates an example of a procedure in which a second base station transmits system information according to one embodiment of the present disclosure.

[0027] FIG. 12 illustrates an example of a procedure in which a second base station transmits synchronized system information based on a reference time according to one embodiment of the present disclosure.

[0028] FIG. 13 illustrates an example of a procedure in which a terminal obtains system information according to one embodiment of the present disclosure.

[0029] FIG. 14 illustrates an example of a procedure for mediating synchronized system information based on a reference time according to one embodiment of the present disclosure.

[0030] The terms used in these embodiments have been selected to be as widely used and general as possible, taking into account the functions within these embodiments; however, these terms may vary depending on the intent of those skilled in the art, case law, the emergence of new technologies, etc. Additionally, in specific cases, the applicant has arbitrarily selected terms, and in such cases, their meanings will be described in detail in the relevant sections. Therefore, the terms used in these embodiments should be defined not merely by their names, but based on their meanings and the content throughout these embodiments.

[0031] The embodiments are subject to various modifications and may take various forms; therefore, some embodiments are illustrated in the drawings and described in detail. However, this is not intended to limit the embodiments to the specific disclosed forms, and it should be understood that the embodiments include all modifications, equivalents, and substitutions that fall within the spirit and scope of the embodiments. The terms used herein are for the description of the embodiments only and are not intended to limit the embodiments.

[0032] Unless otherwise defined, the terms used in these embodiments have the same meaning as generally understood by those skilled in the art to which these embodiments pertain. Terms such as those defined in commonly used dictionaries should be interpreted as having a meaning consistent with their meaning in the context of the relevant technology, and should not be interpreted in an ideal or overly formal sense unless explicitly defined in these embodiments.

[0033]

[0034] Recently, Non-Terrestrial Networks (NTN) technology, which provides global communication services through NG-RAN (Next Generation-Radio Access Network) utilizing Low Earth Orbit (LEO) satellites as base stations, is being actively researched. In the case of existing transparent payloads, satellites can operate in the same way as the relay structure of existing ground base stations, performing frequency filtering, conversion, and signal amplification. Therefore, satellites with a bentpipe structure necessarily require a connection structure with ground base stations. That is, for satellites with a bentpipe structure, inter-satellite connection is not essential, and for example, the Xn interface of the ground network can be used for message exchange between base stations.

[0035]

[0036] FIG. 1 illustrates an example of a network according to one embodiment of the present disclosure.

[0037] Referring to FIG. 1, the network may include a non-terrestrial network and a terrestrial network (TN), and may include a terminal (110), satellites (120-1, 120-2), a gateway (130), and a base station. The terminal (110) is a user device equipped with hardware and software that receives cellular data from a satellite (120-1), and may be a mobile or fixed device. For example, the terminal (110) may include a mobile phone, a smartphone, a wearable device, or a UE (User Equipment). Furthermore, the terminal (110) is not limited to the examples described above, and may include any electronic device capable of cellular communication, such as a laptop or tablet PC. The terminal (110) is not limited to the examples described above. Although the network in FIG. 1 is depicted as including only a single terminal (110), this is merely an exemplary embodiment and is not limited thereto, and it is obvious that it may include multiple terminals (110).

[0038] Specifically, the terminal (110) can support communication protocols defined in 3GPP (3rd generation partnership project) standards (e.g., LTE communication protocol, LTE-A communication protocol, NR communication protocol, etc.). Multiple communication nodes (110 to 130) can support CDMA (code division multiple access) technology, WCDMA (wideband CDMA) technology, TDMA (time division multiple access) technology, FDMA (frequency division multiple access) technology, OFDM (orthogonal frequency division multiplexing) technology, Filtered OFDM technology, CP (cyclic prefix)-OFDM technology, DFT-s-OFDM (discrete Fourier transform-spread-OFDM) technology, OFDMA (orthogonal frequency division multiple access) technology, SC (single carrier)-FDMA technology, NOMA (non-orthogonal multiple access) technology, GFDM (generalized frequency division multiplexing) technology, FBMC (filter bank multi-carrier) technology, UFMC (universal filtered multi-carrier) technology, SDMA (space division multiple access) technology, etc.

[0039] Satellites (120-1, 120-2) fly in a fixed orbit and can provide a cell with coverage of a certain size by forming a beam toward the ground. In relation to the present disclosure, satellite (120-1) may refer to a serving satellite and satellite (120-2) may refer to a target satellite. Additionally, the serving satellite and the target satellite may be referred to as a serving cell and a target cell, respectively, and may be used interchangeably. Furthermore, in the present disclosure, satellites (120-1, 120-2) may be collectively referred to as non-ground cells. A gateway (130) provides the satellites (120-1, 120-2) with a link to connect to a network. A base station (140) may refer to a terrestrial base station or a wireless communication device fixed at a specific location and can provide a cell with coverage of a certain size. In connection with the present disclosure, satellites (120-1, 120-2) and base station (140) may be referred to as gNB (gNodeB) or cell. Additionally, in the present disclosure, the last cell to which the terminal (110) was previously connected may be mentioned, and said last cell may be referred to as last gNB, Last Serving gNB, source cell, etc.

[0040] The link between the terminal (110) and the satellite (120-1) is called a service link and may be based on NR standards defined by 3GPP. The link between the satellites (120-1, 120-2) and the gateway (130) is called a feeder link and may be based on a 3GPP or non-3GPP wireless interface. The link between satellites may be used mainly for regenerative satellites.

[0041] For transparent satellites based on an NR-RAN architecture, the satellite radio interfaces of the feeder link and service link may be NR-Uu. For transparent satellites, the satellite performs radio frequency filtering, frequency conversion, and amplification functions. For regenerative satellites, onboard functions are built into the satellite, and accordingly, the satellite can perform radio frequency filtering, frequency conversion, and amplification, as well as some or all of the base station functions such as switching and routing, coding and modulation, and decoding and demodulation.

[0042]

[0043] FIG. 2 illustrates another example of a network according to one embodiment of the present disclosure. FIG. 3 illustrates an example of an NTN providing non-terrestrial access to a UE (210) using an NTN payload (220) and an NTN gateway (230). Here, the UE (210) may be substantially the same configuration as the terminal (110) described in FIG. 1. Referring to FIG. 2, the link between the NTN payload (220) and the UE (210) is a service link and may be based on a Uu interface. The link between the NTN payload (220) and the NTN gateway (230) is a feeder link. The link between the NTN gateway (230) and the AMF / UPF (240) may be based on an NG interface. The NTN payload (220) can transparently forward wireless protocols received from the UE (210) to the NTN gateway (230) via the service link. Similarly, the NTN payload (220) can transparently forward wireless protocols received from the NTN gateway (230) via a feeder link to the UE (210).

[0044] To this end, the following connectivity may be supported by the NTN payload (220). A base station may service multiple NTN payloads. An NTN payload may be serviced by multiple base stations.

[0045] The NTN payload (220) can change the carrier frequency before retransmitting data on the service link. That is, the NTN payload (220) can use different carrier frequencies on the service link and the feed link. For the NTN, at least one of the following may be used as a network identifier: AMF name, NCGI (NR cell global identifier), CgNB ID (identifier), global gNB ID, TAI (tracking area identity), S-NSSAI (Single Network Slice Selection Assistance information), NSAG (Network Slice AS Group), NID (Network Identifier), CAG (Closed Access Group) ID, and local NG-RAN node ID (identifier). Additionally, a mapped cell ID may be used. Here, the tracking area may correspond to a fixed geographical area.

[0046] Non-geosynchronous orbits (NGSO) include a low Earth orbit at an altitude of about 300 km to 1500 km and a medium Earth orbit at an altitude of about 7000 km to 25000 km.

[0047] Service links can be classified into the following three types: earth-fixed, quasi-earth-fixed, and earth-moving. The earth-fixed type provides beam(s) that continuously cover the same geographical area at all times. For example, a satellite in a geosynchronous orbit (GSO) can provide an earth-fixed type service link. The quasi-earth-fixed type provides beam(s) that continuously cover the same geographical area for a limited period and beams that cover different geographical areas during different periods. For example, a satellite in a non-earth-synchronous orbit can provide a quasi-earth-fixed type service link using steerable beams. The earth-moving type provides beams where the coverage area slides across the Earth's surface. For example, a satellite with a non-Earth-synchronous orbit can provide an Earth-moving type service link using fixed or steerable beams.

[0048] By using a satellite with a non-Earth-synchronous orbit, the base station can provide quasi-Earth-fixed cell coverage or Earth-mobile cell coverage. By using a satellite with an Earth-synchronous orbit, the base station can provide Earth-fixed cell coverage. In the case of a non-Earth-synchronous orbit, a switch of the service link may be referred to a change of the serving satellite (120-1).

[0049]

[0050] FIG. 3 illustrates the configuration of a device in a wireless communication system according to one embodiment of the present disclosure. The device of FIG. 3 may be understood as a part of the structure of any one of the devices described with reference to FIG. 1, for example, a terminal (110), satellites (120-1, 120-2), a gateway (130), and a base station (140).

[0051] Referring to FIG. 3, the device may include a processor (310), a communication unit (320), and a memory (330).

[0052] The processor (310) can control the overall function and operation of the device. The processor (310) may include an application-specific integrated circuit (ASIC), other chipsets, logic circuits, and / or data processing devices.

[0053] The communication unit (320) is connected to the processor (310) to transmit and receive wireless signals. The communication unit (320) may include a baseband circuit for processing wireless signals. For example, the communication unit (320) may include a short-range communication unit, a mobile communication unit, and a broadcast reception unit. In one embodiment, the communication unit (320) may transmit and receive data to and from other devices, such as a base station, a satellite, etc.

[0054] Memory (330) is hardware that stores various data processed by the processor (310). For example, the memory (330) may store SIR values ​​for the transmission target terminals of the transmitting terminals, information regarding transmission target terminal groups for each transmitting terminal, etc. Additionally, the memory (330) may store applications, drivers, etc. to be driven by the processor (310). The memory (330) may include RAM (random access memory) such as DRAM (dynamic random access memory) and SRAM (static random access memory), ROM (read-only memory), EEPROM (electrically erasable programmable read-only memory), CD-ROM, Blu-ray or other optical disc storage, HDD (hard disk drive), SSD (solid state drive), or flash memory.

[0055] The structure of FIG. 3 can be understood as at least part of a terminal, base station, satellite, or gateway. If the structure of FIG. 3 is part of a satellite, the satellite may include other hardware devices necessary for orbiting in addition to the components illustrated in FIG. 3.

[0056]

[0057] FIG. 4 illustrates an example of a transparent satellite-based network according to one embodiment of the present disclosure. Through FIG. 4, a communication method of a transparent satellite-based network is described.

[0058] Referring to FIG. 4, the terminal can be configured to communicate with a transparent satellite through a wireless interface, NR-Uu. Here, the transparent satellite has a transparent payload structure and can relay the received wireless signal to a ground station.

[0059] The transparent satellite is linked to the NTN gateway, and the NTN gateway can transmit NR-Uu interface signals received from the transparent satellite to the terrestrial network. The NTN gateway is connected to a terrestrial base station, and the terrestrial base station can communicate with the 5G Core Network (5G CN) through the NG interface.

[0060] The 5G core network can be configured to receive data from ground base stations via the NG interface and to interact with an external data network via the N6 interface. Meanwhile, the transparent satellite and the NTN gateway can operate as part of a remote radio unit.

[0061]

[0062] FIG. 5 illustrates an example of a regenerative satellite-based network according to an embodiment of the present disclosure. A communication method of a regenerative satellite-based network is described through FIG. 4. Since 3GPP Release 19, standardization has been proceeding with the regenerative satellite payload as the main architecture, which is a structure in which base stations are mounted on satellites. Unlike conventional satellites that are merely relays, regenerative satellites operate in a structure in which they communicate with each other through links between satellites as they perform the role of base stations, and exchange data through Xn interfaces between base stations. The regenerative satellite-based network environment is described as the NG-RAN architecture structure of 3GPP TR 38.821, as shown in FIG. 5 below.

[0063] Referring to FIG. 5, the terminal can be configured to communicate with a regenerative satellite through a wireless interface, NR-Uu. Here, the regenerative satellite has a regenerative payload structure, and a base station is implemented to perform demodulation or coding processing on a signal received from the terminal.

[0064] Regeneration satellites can implement inter-satellite links through the Xn interface. In other words, regeneration satellites can perform inter-satellite message exchange and resource control via the Xn interface without passing through a separate terrestrial network. Additionally, regeneration satellites can be connected to NTN gateways via the Satellite Radio Interface (SRI).

[0065] The regenerative satellite can communicate directly with the 5G Core Network (5G CN) through the NG interface. The 5G Core Network can be configured to receive data from the regenerative satellite through the NG interface and to interact with an external data network through the N6 interface.

[0066]

[0067] When a network is constructed using regenerative satellite payloads, the Application Protocol (hereinafter XnAP) can be utilized via the Xn interface between satellites, just as in existing terrestrial networks. With the regenerative satellite payload structure currently being standardized in 3GPP Release 19, extending XnAP to suit non-terrestrial network environments is essential. Meanwhile, in non-terrestrial network environments where regenerative satellite payloads are applied, XnAP operates via a wireless optical network rather than a wired network; consequently, the following technical challenges exist for applying existing XnAP procedures.

[0068] Conventional XnAP is designed based on wired network connections between fixed ground base stations and is currently defined in the 3GPP TS 38.423 document. According to existing procedures, the process of establishing Xn interface connections is managed through Xn Setup and Xn Removal procedures, respectively. However, since satellites in a regenerative satellite payload environment move at high speeds, inter-satellite links—i.e., Xn interface connections—change dynamically, and link disconnections occur frequently. In such an environment, there are limitations to applying conventional XnAP procedures directly to a regenerative satellite payload environment. In particular, conventional standards do not define procedures for checking the connection status of dynamic wireless links in advance or for removing the corresponding link in the event of a disconnection. This implies that since inter-satellite links consist of wireless optical communication between satellites, unlike existing ground wired networks, the characteristics of wireless links must be reflected in XnAP as well.

[0069] In addition, in a non-terrestrial network environment, a user terminal needs to acquire System Information (hereinafter SI) regarding not only the serving satellite but also a number of adjacent surrounding satellites in order to perform a smooth handover. According to the prior art, the terminal receives a Master Information Block (MIB) via a Primary / Secondary Synchronization Signal (PSS / SSS) and can receive a System Information Block Type 1 (SIB1) via the MIB. SIB1 contains si-SchedulingInfo, through which the terminal can check scheduling information regarding whether other system information (Other System Information, OSI, e.g., SIB2 or higher) is broadcast. This information is the minimum information that the terminal can receive without performing a Random Access Channel (RACH) procedure.

[0070] Meanwhile, as defined in 3GPP TS 38.331, if a terminal fails to verify other necessary system information from si-SchedulingInfo, the terminal may transmit a SystemInfoRequest message to request on-demand system information using the Common Control Channel (CCCH). However, the SystemInfoRequest message is transmitted only when the terminal is in the RRC_IDLE or RRC_INACTIVE state. This is because a terminal in the RRC_CONNECTED state is uplink synchronized only with the serving cell, and the RACH procedure must be performed for SystemInfoRequest. Therefore, a terminal in the RRC_CONNECTED state can request system information only from the serving satellite and cannot directly obtain system information from surrounding satellites where no RRC connection exists. If the terminal attempts to individually connect with surrounding satellites to request information, problems such as massive latency, signaling overhead, and resource waste may occur.

[0071] Furthermore, in a satellite network environment, position and time information included in SIB19 can be utilized for distance-based handover and Timing Advance (TA) correction. However, when a terminal receives position information from multiple nearby satellites, including a serving satellite, such information may not have been measured at the same point in time, which can cause errors during handover determination. For example, under the condition condEventD2, a handover is performed based on the change in distance (referenceLocation) between the cell center and the terminal. However, if referenceLocation information measured at different points in time is used, errors may accumulate, leading to abnormal handovers. Additionally, if a terminal simultaneously receives time-synchronized system information from multiple satellites, there is a possibility of excessive signaling overhead.

[0072] Therefore, to solve the aforementioned problems, the present disclosure proposes a method for efficiently acquiring system information based on inter-satellite interfaces. Specifically, it proposes a relay-based SIB exchange procedure in which a serving satellite relays a request from a terminal to efficiently acquire system information from surrounding satellites and provide time-synchronized information to the terminal.

[0073]

[0074] FIG. 6 illustrates an example of a procedure for acquiring System Information according to an embodiment of the present disclosure. The first base station (604) of FIG. 6 may be a non-ground cell that is a serving cell and a regeneration satellite. Additionally, the second base station (606) may be a target cell and a non-ground cell that is a regeneration satellite. Base stations mentioned in the following disclosure may be referred to as nodes and RAN nodes, etc. FIG. 6 illustrates the problems of the existing SIB acquisition procedure. The terminal (602) of FIG. 6 is described on the premise that it is in an RRC_CONNECTED state with the first base station (604).

[0075] Referring to FIG. 6, in step S601, the terminal (602) can receive the MIB. For example, the terminal (602) can obtain the MIB through PSS / SSS.

[0076] In step S603, the terminal (602) can obtain a system information message. For example, the terminal (602) can obtain SIB1 (System Information Block Type 1) through the MIB. SIB1 contains si-SchedulingInfo, and the terminal (602) can check scheduling information regarding whether SIB2 or other system information is broadcast.

[0077] In step S605, the terminal (602) transmits a System Information Request (SIRequest) message to the first base station (604), and in step S607, it can receive the System Information message from the first base station (604). That is, the terminal (602) can request System Information only from the first base station (604) which is in the RRC_CONNECTED state, and cannot directly request an on-demand SIB from the second base station (606), which is a surrounding satellite that is a handover candidate.

[0078]

[0079] For smooth handover in an NTN environment, ephemeris information from surrounding satellites, such as SIB19, is required. However, there are limitations in that if a terminal attempts to establish an RRC connection individually with surrounding satellites and requests information such as SIB19, it causes significant signaling overhead and delay. Therefore, the present disclosure discloses a procedure in which a terminal obtains system information without establishing an RRC connection with surrounding satellites by having a serving satellite mediate system information.

[0080]

[0081] FIG. 7 illustrates an example of a procedure for obtaining system information based on the interface of a first base station according to an embodiment of the present disclosure. The first base station (704) of FIG. 7 may be a non-ground cell that is a serving cell and a regeneration satellite. Additionally, the second base station (706) may be a non-ground cell that is a target cell and a regeneration satellite. The terminal (702) of FIG. 7 is described on the premise that it is in an RRC_CONNECTED state with the first base station (704).

[0082] Referring to FIG. 7, in step S701, the terminal (602) can receive the MIB. For example, the terminal (702) can obtain the MIB through PSS / SSS.

[0083] In step S703, the terminal (702) can obtain a system information message. For example, the terminal (702) can obtain SIB1 through the MIB. SIB1 contains si-SchedulingInfo, and the terminal (702) can check scheduling information regarding whether SIB2 or other system information is broadcast.

[0084] In step S705, the terminal (702) transmits a system information request message to the first base station (704). That is, the terminal (702) can transmit a system information request message to the first base station (704) which is in the RRC_CONNECTED state to obtain system information of a surrounding base station. The system information request message may include a list of system information required by the terminal (702) for handover, link connection, etc., and at least one list of base stations corresponding to the system information list.

[0085] In step S707, the first base station (704) transmits a system information request message to the second base station (706). For example, the first base station (704) may integrate the system information request message received from the terminal (702) and transmit the system information request message to the second base station (706). Specifically, the first base station (704) may transmit a system information request message in the form of XnAP to the satellite corresponding to the base station requested by the terminal by using an Xn interface established through a satellite link. That is, the first base station (704) may comprehensively process signals with surrounding satellites based on the request of the terminal (702) and perform the role of mediating the system information request message of the terminal (702). FIG. 7 is illustrated as receiving a request from a single terminal (702) and transmitting a system information request message to a single target, a second base station (706), but is not limited thereto, and may receive system information request messages from multiple terminals and transmit system information request messages to a base station corresponding to at least one base station list included in the system information request message.

[0086] In step S709, the first base station (704) receives a system information message from the second base station (706). The first base station (704) may receive a system information message from a base station corresponding to at least one base station list included in the system information request message. Specifically, the first base station (704) may receive SIBs corresponding to the system information list included in the system information request message in the form of XnAP response messages. For example, the system information may include SIB19 and other system information.

[0087] In step S711, the first base station (704) transmits a system information message to the terminal (702). The first base station (704) may aggregate system information received from each surrounding satellite and transmit it to the terminal (702) using a single or consecutive RRC message. Specifically, the first base station (704) may package a system information message received from a base station corresponding to the base station list requested by the terminal (702) and transmit it to the terminal (702). For example, the first base station (704) may package a system information message received from the second base station (706) and transmit it to the terminal (702). The first base station (704) may package SIBs based on the system information list, the identifiers of the base stations, the types of SIBs, and the original data of the SIBs. For example, the first base station (704) may distinguish between SIB19 and other SIBs and package them. In the case of system information messages in which other SIBs are packaged, the first base station (704) can transmit to the terminal (702) via a dedicated RRC message called a SIM (System Information messages).

[0088] That is, the first base station (704), which is the serving satellite, can immediately package the SIB information of the requested surrounding satellites and deliver it directly without delay to the terminal in the RRC_CONNECTED state. This reduces unnecessary broadcast overhead and ensures that the terminal (702) can quickly obtain the necessary information.

[0089] Meanwhile, SIB19 includes an element called ntn-NeighCellConfigList, as in the 3GPP standard TS 38.331. ntn-NeighCellConfigList includes an NTN-Config element among the SIB information for neighboring cells, and there is an item that can include basic NTN-related information of neighboring cells. Accordingly, according to the embodiment, the first base station (702) can first check whether the NTN-Config information of a neighboring cell is included in the ntn-NeighCellConfigList within SIB19. That is, according to the embodiment, the first base station (702) can transmit system information of a neighboring cell only if the NTN-Config information of a neighboring cell is not included in the NTN-Config element.

[0090]

[0091] The system information mentioned in the present disclosure may be packaged based on the container information elements of Table 1 below.

[0092]

[0093] NeighbourSIB-ContainerList: Information element (IE) A container in the form of a list that may be included in messages such as RRCReconfiguration (Sub-) neighbourCellID: An ID identifying the neighboring satellite that is the source of the information requestedSIB-List: A list of SIB information received from the relevant satellite (Sub-) sib-Type: The type of SIB being transmitted (e.g., SIB2, SIB3) sib-Payload: The original data of the relevant SIB (OCTET STRING)

[0094] The structure in Table 1 may be referred to as a 1-tier SIB packaging structure. NeighborSIB-ContainerList is a container in the form of a list that can be transmitted within an RRCReconfiguration message or other control messages. The container contains one or more sub-information elements, each of which can be used to structure system information, such as SIBs collected from neighboring cells. NeighborCellID may refer to an identifier for identifying the neighboring satellite that is the source of the system information. NeighborCellID may be used to distinguish the satellite from which the terminal transmitted the corresponding system information. requestedSIB-List may contain a list of system information received from neighboring satellites. For example, requestedSIB-List may contain SIBs in the form of a list. sib-Type includes the type of the transmitted SIBs and may include identifiers such as SIB2, SIB3, etc. The sib-payload stores the raw data of the SIBs in the OCTET STRING format and may include the actual content of the corresponding SIB.

[0095]

[0096] Handover procedures performed in an NTN environment are based on satellite ephemeral information and geometric parameters. Therefore, it is important that position information between the serving satellite and surrounding satellites is measured at the same time reference. If position information measured at different points in time is used for handover, measurement discrepancies and judgment errors may occur in the terminal's handover decision or distance-based position correction procedure. Nevertheless, conventionally, there has been a lack of procedures to acquire synchronized parameters when the serving satellite collects position information from surrounding satellites, such as specifying a particular reference time or aligning position information at the same reference point. Accordingly, this disclosure proposes a procedure for acquiring and updating information based on time synchronization.

[0097]

[0098] FIG. 8 illustrates an example of a procedure for obtaining synchronized system information based on a reference time according to one embodiment of the present disclosure. The first base station (804) of FIG. 8 may be a non-ground cell that is a serving cell and a regeneration satellite. Additionally, the second base station (806) may be a non-ground cell that is a target cell and a regeneration satellite. The terminal (802) of FIG. 8 is described on the premise that it is in an RRC_CONNECTED state with the first base station (804).

[0099] Referring to FIG. 8, in step S801, the first base station (804) transmits a system information message to the terminal (802). The system information message may be transmitted at reference times determined based on a predetermined timer. Specifically, the reference time is the time when the terminal (802) receives the system information message ( It can be calculated from ). In addition, the reference time at which the next system information message is transmitted ( ) is the time at which the system information message was received and a predetermined timer ( It can be determined based on ). For example, the reference time is the time when the first base station (804) transmits SIB19 to the terminal (802). It can be calculated from ). Meanwhile, although there may be some physical error between the time when the first base station (804) transmits SIB19 and the time when the terminal (802) receives SIB19, the present disclosure explains it on the premise that there is no error.

[0100] In step S803, the first base station (804) transmits a system information request message to the second base station (806). For example, the first base station (804) may transmit a system information request message to the second base station (806) based on a system information request message received from the terminal (802). Specifically, the first base station (804) may integrate the system information request message received from the terminal (802) and transmit it to the second base station (806). Specifically, the first base station (804) may transmit a system information request message in the form of XnAP to the satellite corresponding to the base station requested by the terminal using an Xn interface established through a satellite link. Meanwhile, the system information request message may be transmitted in the form of an ntn-ephConfigRequest message. Step S803 can be understood as a procedure that, rather than simply requesting system information, specifies location information at a reference time and requests the specified location information.

[0101] In step S805, the second base station (806) calculates location information. The second base station (806) obtains location information at reference times based on celestial ephemeris information. That is, the second base station (806) obtains location information synchronized with reference times.

[0102] In step S807, the second base station (806) transmits a system information message to the first base station (804). For example, the second base station (806) may transmit location information synchronized with reference times to the first base station (804) in the form of an ntn-ephConfig response message (e.g., SI Request ACK message or ntn-ephConfigResponse message).

[0103] In step S809, the first base station (804) generates system information. The first base station (804) can collect all location information synchronized based on reference times from itself and the second base station (804) and generate packaged system information. For example, the first base station (804) can package system information based on a system information list, identifiers of base stations, types of SIBs, original data of SIBs, and location information. For example, the first base station (704) can distinguish and package SIB19 and other SIBs of system information. Meanwhile, the first base station (804) can store the location information in ntn-NeighCellConfigList or aggregate it into separate internal parameters. That is, the first base station (804) can newly configure system information for the next cycle based on location information synchronized based on reference times.

[0104] In step S811, the first base station (804) transmits a system information message to the terminal (802). Specifically, the first base station (804) transmits the next reference time ( ) can transmit a system information message. For example, the first base station (804) can transmit the next reference time ( This new SIB19 can be transmitted to the terminal (802). System information messages can be broadcast.

[0105] In conclusion, even if the terminal (802) receives only a single SIB19 message from the first base station (804), which is the serving satellite, it is possible to make an accurate distance-based handover determination without time error because the message includes location information based on the same time point for the serving satellite itself and all surrounding satellites. Additionally, the first base station (804) collects information and transmits it to the terminal (802), thereby reducing the overhead of the access link.

[0106]

[0107] A predetermined timer ( ) can be determined based on information indicating the period of system information. For example, a predetermined timer ( ) may be determined based on scheduling information of other system information. The said scheduling information may include si-periodicity defined in SIB1 of 3GPP TS 38.331. When si-periodicity expires, the terminal must receive SIB19 again. For example, si-periodicity may include information about radio frames. Additionally, the scheduling information may include information indicating whether a SIB or posSIB is included in the system message. For example, information indicating whether a SIB or posSIB is included in the system message may be referred to as sib-MappingInfo. Before the timer expires, the serving satellite determines the next reference time to be used for the next SIB19 update ( ) can be determined in advance. The reference time can serve as a common reference point for all satellites to calculate position information. The reference time serves as a reference point for determining position information, and the reference times ( ) can be determined by the following mathematical formula 1.

[0108] [Mathematical Formula 1]

[0109] , n is 0~1

[0110] The serving satellite can determine the reference time for measurements of information requiring time synchronization with surrounding satellites by using the reference times for retransmitting SIB19. For example, according to Equation 1, the reference time ( )silver class It can be determined as the time between. In this disclosure, for convenience of description, the following reference time is n=1, Explained on the premise that

[0111]

[0112] FIG. 9 illustrates an example of a procedure in which a first base station acquires system information according to one embodiment of the present disclosure. The operating entity of FIG. 9 is described as a device, but depending on the embodiment, it may be a serving satellite. The serving satellite may be referred to as the first base station.

[0113] Referring to FIG. 9, in step S901, the device receives a system information request message from a terminal. The device may receive a system information request message from a terminal in the RRC_CONNECTED state to obtain system information of a nearby base station. The system information request message may include a list of system information required by the terminal for handover, link connection, etc., and at least one list of base stations corresponding to the system information list.

[0114] In step S903, the device transmits a system information request message to a second base station. The second base station may be any one of the base station lists included in the system information request message. The device may integrate system information request messages received from terminals and transmit the system information request messages to each base station. Specifically, the device may transmit a system information request message in the form of XnAP to the satellite corresponding to the base station requested by the terminal, using an Xn interface established via an inter-satellite link. That is, the device may perform the role of comprehensively processing signals with surrounding satellites based on the terminal's request and mediating the terminal's system information request message.

[0115] In step S905, the device receives a system information message from a second base station. The device may receive the system information message from the second base station included in the list of base stations included in the system information request message. Specifically, the device may receive SIBs corresponding to the list of system information included in the system information request message in the form of XnAP response messages. For example, the system information may include SIB19 and other system information.

[0116] In step S907, the device transmits a system information message to the terminal. The device aggregates system information received from the second base station and can transmit it to the terminal using a single or consecutive RRC message. Specifically, the device can package a system information message received from a base station corresponding to the base station list requested by the terminal and transmit it to the terminal. For example, the device can package a system information message received from the second base station and transmit it to the terminal. The device can package SIBs based on the system information list, base station identifiers, SIB types, and original data of the SIBs. For example, the device can distinguish between SIB19 and other SIBs and package them. In the case of a system information message containing other SIBs, the device can transmit it to the terminal via a dedicated RRC message called a SIM (System Information message).

[0117]

[0118] FIG. 10 illustrates an example of a procedure in which a first base station acquires synchronized system information based on a reference time according to one embodiment of the present disclosure. The operating entity of FIG. 10 is described as a device, but depending on the embodiment, it may be a serving satellite. The serving satellite may be referred to as the first base station.

[0119] Referring to FIG. 10, in step S1001, the device transmits a system information message to a terminal. The system information message may be transmitted at reference times determined based on a predetermined timer.

[0120] In step S1003, the device calculates a reference time. For example, the device at the time when it sent a system information message to the terminal ( ) can be determined as the reference time. For example, the reference time is the time when the device transmits SIB19 to the terminal ( It can be calculated from ). In addition, the device uses the reference time when the next system information message is transmitted ( ) the time at which a system information message was transmitted to the terminal and a predetermined timer ( It is determined based on ).

[0121] In step S1005, the device transmits a system information request message including a reference time to the second base station. For example, the device may transmit a system information request message to the second base station based on a system information request message received from the terminal. Specifically, the device may integrate the system information request message received from the terminal and transmit it to the second base station. Specifically, the device may transmit a system information request message in the form of XnAP to the satellite corresponding to the base station requested by the terminal using an Xn interface established through a satellite-to-satellite link. Meanwhile, the system information request message may be transmitted in the form of an ntn-ephConfigRequest message.

[0122] In step S1007, the device receives a system information message containing location information from the second base station. For example, the device may receive location information synchronized with reference times as a response message in the form of ntn-ephConfig (e.g., SI Request ACK message or ntn-ephConfigResponse message).

[0123] In step S1009, the device generates system information based on reference times. The device may package location information received from itself and the second base station and generate system information. For example, the device may package system information based on a system information list, base station identifiers, types of SIBs, original data of SIBs, and location information. For example, the device may distinguish and package SIB19 and other SIBs of system information. Meanwhile, the device may store the location information in ntn-NeighCellConfigList or aggregate it into separate internal parameters. That is, the device may reconfigure system information for the next cycle based on location information synchronized based on reference times.

[0124] In step S1011, the device transmits a system information message to the terminal at a reference time. Specifically, the device at the next reference time ( System information messages can be transmitted based on ). For example, the device can transmit the following reference time ( This new SIB19 can be transmitted to the terminal. System information messages can be broadcast.

[0125]

[0126] FIG. 11 illustrates an example of a procedure in which a second base station transmits system information according to one embodiment of the present disclosure. The operating entity of FIG. 11 is described as a device, but depending on the embodiment, it may be a target satellite. The target satellite may be referred to as the second base station.

[0127] Referring to FIG. 11, in step S1101, the device receives a system information request message from the first base station. The device may be any one of the base station lists included in the system information request message. The device may receive a system information request message in the form of XnAP from the first base station using an Xn interface established via a satellite link. The system information request message may be received from the first base station as the terminal transmits the system information request message to the first base station. Meanwhile, the system information request message may be transmitted in the form of an ntn-ephConfigRequest message.

[0128] In step S1103, the device transmits a system information message to the first base station. Specifically, the device may transmit SIBs corresponding to the list of system information included in the system information request message in the form of an XnAP response message. For example, the system information may include SIB19 and other system information.

[0129]

[0130] FIG. 12 illustrates an example of a procedure in which a second base station transmits synchronized system information based on a reference time according to one embodiment of the present disclosure. The operating entity of FIG. 12 is described as a device, but depending on the embodiment, it may be a target satellite. The target satellite may be referred to as the second base station.

[0131] In step S1201, the device receives a system information request message from the first base station that includes a reference time. The device may receive the system information request message in the form of XnAP from the first base station using an Xn interface established via an inter-satellite link. Meanwhile, the system information request message may be transmitted in the form of an ntn-ephConfigRequest message. The reference time is the time at which the terminal receives the system information message from the first base station ( ) can be determined as the reference time. For example, the reference time is the time when the terminal receives SIB19 from the first base station ( It can be calculated from ). In addition, the reference time at which the next system information message is transmitted ( ) is the time when the terminal receives the system information message and a predetermined timer ( It can be determined based on ).

[0132] In step S1203, the device calculates position information based on a reference time. The device obtains position information for the reference time based on ephemeral information. That is, the device obtains position information synchronized with reference times.

[0133] In step S1205, the device transmits a system information message containing location information to the first base station. For example, the device transmits a system information message containing location information synchronized with reference times to the first base station. For example, the device may transmit the location information to the first base station in the form of ntn-ephConfig, contained in a response message (e.g., SI Request ACK message or ntn-ephConfigResponse message).

[0134]

[0135] FIG. 13 illustrates an example of a procedure in which a terminal obtains system information according to one embodiment of the present disclosure. The operating entity of FIG. 12 is described as a device, but depending on the embodiment, it may be a terminal.

[0136] Referring to FIG. 13, the device transmits a request message to a first base station. The device may transmit a system information request message to a first base station in the RRC_CONNECTED state to obtain system information of a surrounding base station. The system information request message may include a list of system information required for handover, link connection, etc., and at least one list of base stations corresponding to the system information list.

[0137] In step S1303, the device may receive a system information message from the first base station. The system information message may be obtained from a base station corresponding to the base station list. Specifically, the device may repeatedly receive the system information message based on a reference time. The reference time is the time when the device receives SIB19 ( It can be calculated from ). In addition, the reference time at which the message is received ( ) is the time at which the system information message was received and a predetermined timer ( It can be determined based on ). The device has the following reference time ( System information messages can be transmitted based on ). For example, the device can transmit the next reference time ( This new system information message can be received at ). The system information message can be broadcast. Meanwhile, the system information message may include a list of system information, identifiers of base stations, types of SIBs, original data of SIBs, and location information.

[0138]

[0139] FIG. 14 illustrates an example of a procedure for mediating system information synchronized based on a reference time according to one embodiment of the present disclosure. Specifically, FIG. 14 illustrates a process of obtaining NTN location information synchronized with a reference time and updating SIB19 through communication between a terminal (UE), a serving satellite (Serving SAT), and a neighbor satellite (Neighbor SAT).

[0140] Referring to FIG. 14, the terminal receives only SIB19 broadcast from the serving satellite, and at the time SIB19 is received ( It stores ). Meanwhile, the serving satellite may maintain the same communication synchronization as the terminal.

[0141] For the generation of SIB19 for the next cycle, the serving satellite uses a reference time from an adjacent satellite ( It is necessary to obtain location information corresponding to ). Therefore, the serving satellite transmits an ntn-ephConfig Request message to an adjacent satellite, and the reference time ( Requests location information at ).

[0142] The adjacent satellite obtains position information corresponding to the reference time based on ephemeris information. The adjacent satellite generates ntn-ephConfig containing the position information and transmits it to the serving satellite.

[0143] The serving satellite integrates ntn-ephConfig information collected from itself and adjacent satellites and constructs ntn-NeighCellConfigList. ntn-NeighCellConfigList is an information block containing the positions, orbits, reference times, etc., of surrounding satellites, and is used when generating SIB19 for the next cycle. That is, the serving satellite generates a new SIB19 using the time-synchronized position information of itself and adjacent satellites, and broadcasts it to the terminal at the next reference time.

[0144] The next reference time is the time when SIB19 was transmitted to the terminal ( It can be determined by adding scheduling information to ). The next reference time is the time when SIB19 was transmitted to the terminal ( It can be determined by reflecting si-periodicity in ). For example, the serving satellite sets a timer for the time when half of the si-periodicity is reached, and the time when SIB19 is transmitted to the terminal ( Starting with ), a new SIB19 can be transmitted to the terminal before the timer is completed. si-periodicity may refer to scheduling information defined in SIB1 of 3GPP TS 38.331.

[0145]

[0146] Meanwhile, those skilled in the art related to the present embodiment will understand that it may be implemented in modified forms without departing from the essential characteristics of the above description. Therefore, the disclosed methods should be considered in an illustrative rather than a restrictive sense. The scope of the present disclosure is defined by the claims, not by the foregoing description, and all variations within the scope of equivalence should be interpreted as being included in the present disclosure.

[0147] The present disclosure relates to a wireless communication system, and in particular, can be used in a device for acquiring system information (SI) between base stations in a wireless communication system.

Claims

1. In a method of operating a first base station in a wireless communication system, A step of receiving a System Information (SI) request message from a terminal; A step of transmitting the system information request message to the second base station; A step of receiving a system information message from the second base station; and A method comprising the step of transmitting the system information message to the terminal.

2. In Paragraph 1, The above system information request message is, A method comprising a system information list and at least one base station list corresponding to the system information list.

3. In Paragraph 1, The step of transmitting a system information request message to the second base station is: A method comprising the step of transmitting the system information request message to a base station corresponding to at least one base station list included in the system information request message.

4. In Paragraph 1, The step of transmitting the above system information message is, A method comprising the step of transmitting the system information message for each reference time determined based on a predetermined timer.

5. In Paragraph 4, The above reference times are, A method determined based on the time at which the terminal receives the system information message and the predetermined timer.

6. In Paragraph 4, The above system information request message is, Including the above reference times, The above system information message is, A method comprising location information for the second base station synchronized with the above reference times.

7. In Paragraph 4, The step of transmitting the above system information message is, A method comprising the step of transmitting the system information message synchronized based on the above reference times.

8. In Paragraph 4, The above predetermined timer is, A method determined based on information indicating the cycle of system information.

9. In Paragraph 8, The information indicating the period of the above-mentioned system information is, A method determined based on scheduling information of Other System Information (OSI).

10. In a first base station of a wireless communication system, Transmitter / receiver; and It includes a processor connected to the above-mentioned transmitter and receiver, The above processor is, Receive a system information request message from a terminal, and Transmit the above system information request message to the second base station, and Receive a system information message from the above second base station, and A first base station that controls the transmission of the system information message to the terminal.

11. In a method of operating a second base station in a wireless communication system, A step of receiving a system information request message from a first base station; and The method includes the step of transmitting a system information message to the first base station based on the system information request message, A method in which the reception of the system information request message from the first base station is based on the request for a system information message of the terminal.

12. In Paragraph 11, The above system information request message is, A method comprising a system information list and at least one base station list corresponding to the system information list.

13. In Paragraph 11, The step of receiving a system information request message from the first base station is: A method comprising the step of receiving a system information request message based on at least one base station list included in the system information request message.

14. In Paragraph 11, The above system information message is, A method generated based on reference times determined based on a predetermined timer.

15. In Paragraph 14, The above reference times are, A method determined based on the time at which the terminal receives the system information message and the predetermined timer.

16. In Paragraph 14, The above predetermined timer is, A method determined based on information indicating the cycle of system information.

17. In Paragraph 16, The information indicating the period of the above-mentioned system information is, A method determined based on scheduling information of other system information.

18. In a second base station of a wireless communication system, Transmitter / receiver; and It includes a processor connected to the above-mentioned transmitter and receiver, The above processor is, Receive a system information request message from the first base station, and Control to transmit a system information message to the first base station based on the system information request message, The reception of the system information request message from the first base station is based on the request for a system information message from the terminal, at the second base station.

19. In a method of operation of a terminal in a wireless communication system, A step of transmitting a system information request message to a first base station; and The method includes the step of receiving a system information message from the first base station, A method in which the first base station receives the system information message from the second base station based on the reception of the system information request message.

20. In a terminal of a wireless communication system, Transmitter / receiver; and It includes a processor connected to the above-mentioned transmitter and receiver, The above processor is, Transmit a system information request message to the first base station, and Control to receive system information messages from the first base station, A terminal that receives a system information message from a second base station based on the reception of the system information request message by the first base station.

Images