Support for inactive mobility from satellite base station without XN connection

Abstract

A method and apparatus for supporting an inactive mobility from a satellite base station without Xn connection is provided. A core network node receives identification information from a first satellite base station before the first satellite base station leaves an access network-based notification area. The core network node receives a context retrieval request message from a second base station, identifies the first satellite base station based on the identification information, and transmits a context retrieval response message to the second base station in response to the context retrieval request message.

Description

SUPPORT FOR INACTIVE MOBILITY FROM SATELLITE BASE STATION WITHOUT XN CONNECTION

[0001] The present disclosure relates to support for inactive mobility from a satellite base station without Xn connection.

[0002] 3rd Generation Partnership Project (3GPP) Long-Term Evolution (LTE) is a technology for enabling high-speed packet communications. Many schemes have been proposed for the LTE objective including those that aim to reduce user and provider costs, improve service quality, and expand and improve coverage and system capacity. The 3GPP LTE requires reduced cost per bit, increased service availability, flexible use of a frequency band, a simple structure, an open interface, and adequate power consumption of a terminal as an upper-level requirement.

[0003] 3GPP New Radio (NR) targets a single technical framework addressing all usage scenarios, requirements and deployment scenarios including enhanced Mobile BroadBand (eMBB), massive Machine Type Communications (mMTC), Ultra-Reliable and Low Latency Communications (URLLC), etc. The NR shall be inherently forward compatible. Further, the NR should be able to use any spectrum band ranging at least up to 100 GHz that may be made available for wireless communications even in a more distant future.

[0004] 6G is the successor to 5G cellular technology. 6G networks will be able to use higher frequencies than 5G networks and provide substantially higher capacity and much lower latency. The 6G technology market is expected to facilitate large improvements in the areas of imaging, presence technology and location awareness. Working in conjunction with Artificial Intelligence (AI), the 6G computational infrastructure will be able to identify the best place for computing to occur. This includes decisions about data storage, processing and sharing.

[0005] Non-Terrestrial Network (NTN) is being studied. The basic idea of NTN is to deliver 5G / NR service via space (satellite) or air (airborne platform). If it is realized as expected, it would be able to deliver the 5G service to those places where it is technically very difficult or cost too much to deliver with terrestrial network. Some examples of those places would be a remote area like deep forest that would be too costly with terrestrial delivery, or far islands or ship that would be technically almost forbidden in terrestrial connection.

[0006] In an aspect, a method is provided. The method comprises receiving, by a core network node, identification information from a first satellite base station before the first satellite base station leaves an access network-based notification area. The method further comprises receiving, by the core network node, a context retrieval request message from a second base station, identifying, by the core network node, the first satellite base station based on the identification information, and transmitting, by the core network node, a context retrieval response message to the second base station in response to the context retrieval request message.

[0007] In another aspect, an apparatus for implementing the above method is provided.

[0008] FIG. 1 shows an example of a communication system to which implementations of the present disclosure are applied.

[0009] FIG. 2 shows an example of wireless devices to which implementations of the present disclosure are applied.

[0010] FIG. 3 shows an example of NG-RAN architecture to which implementations of the present disclosure are applied.

[0011] FIG. 4 shows an example of NTN to which implementations of the present disclosure are applied.

[0012] FIG. 5 shows another example of NTN to which implementations of the present disclosure are applied.

[0013] FIG. 6 shows another example of NTN to which implementations of the present disclosure are applied.

[0014] FIG. 7 shows an example of a method to which implementations of the present disclosure are applied.

[0015] FIG. 8 shows an example of another method to which implementations of the present disclosure are applied.

[0016] FIGS. 9 to 11 show an example of a procedure for supporting inactive mobility from a satellite on-board gNB without Xn connection to which implementations of the present disclosure are applied.

[0017] The following techniques, apparatuses, and systems may be applied to a variety of wireless multiple access systems. Examples of the multiple access systems include a Code Division Multiple Access (CDMA) system, a Frequency Division Multiple Access (FDMA) system, a Time Division Multiple Access (TDMA) system, an Orthogonal Frequency Division Multiple Access (OFDMA) system, a Single Carrier Frequency Division Multiple Access (SC-FDMA) system, and a Multi Carrier Frequency Division Multiple Access (MC-FDMA) system. CDMA may be embodied through radio technology such as Universal Terrestrial Radio Access (UTRA) or CDMA2000. TDMA may be embodied through radio technology such as Global System for Mobile communications (GSM), General Packet Radio Service (GPRS), or Enhanced Data rates for GSM Evolution (EDGE). OFDMA may be embodied through radio technology such as Institute of Electrical and Electronics Engineers (IEEE) 802.11 (Wi-Fi), IEEE 802.16 (WiMAX), IEEE 802.20, or Evolved UTRA (E-UTRA). UTRA is a part of a Universal Mobile Telecommunications System (UMTS). 3rd Generation Partnership Project (3GPP) Long-Term Evolution (LTE) is a part of Evolved UMTS (E-UMTS) using E-UTRA. 3GPP LTE employs OFDMA in Downlink (DL) and SC-FDMA in Uplink (UL). Evolution of 3GPP LTE includes LTE-Advanced (LTE-A), LTE-A Pro, 5G New Radio (NR) and / or 6G.

[0018] For convenience of description, implementations of the present disclosure are mainly described in regards to a 3GPP based wireless communication system. However, the technical features of the present disclosure are not limited thereto. For example, although the following detailed description is given based on a mobile communication system corresponding to a 3GPP based wireless communication system, aspects of the present disclosure that are not limited to 3GPP based wireless communication system are applicable to other mobile communication systems.

[0019] For terms and technologies which are not specifically described among the terms of and technologies employed in the present disclosure, the wireless communication standard documents published before the present disclosure may be referenced.

[0020] In the present disclosure, "A or B" may mean "only A", "only B", or "both A and B". In other words, "A or B" in the present disclosure may be interpreted as "A and / or B". For example, "A, B or C" in the present disclosure may mean "only A", "only B", "only C", or "any combination of A, B and C".

[0021] In the present disclosure, slash ( / ) or comma (,) may mean "and / or". For example, "A / B" may mean "A and / or B". Accordingly, "A / B" may mean "only A", "only B", or "both A and B". For example, "A, B, C" may mean "A, B or C".

[0022] In the present disclosure, "at least one of A and B" may mean "only A", "only B" or "both A and B". In addition, the expression "at least one of A or B" or "at least one of A and / or B" in the present disclosure may be interpreted as same as "at least one of A and B".

[0023] In addition, in the present disclosure, "at least one of A, B and C" may mean "only A", "only B", "only C", or "any combination of A, B and C". In addition, "at least one of A, B or C" or "at least one of A, B and / or C" may mean "at least one of A, B and C".

[0024] Also, parentheses used in the present disclosure may mean "for example". In detail, when it is shown as "control information (PDCCH)", "PDCCH" may be proposed as an example of "control information". In other words, "control information" in the present disclosure is not limited to "PDCCH", and "PDCCH" may be proposed as an example of "control information". In addition, even when shown as "control information (i.e., PDCCH)", "PDCCH" may be proposed as an example of "control information".

[0025] Technical features that are separately described in one drawing in the present disclosure may be implemented separately or simultaneously.

[0026] Although not limited thereto, various descriptions, functions, procedures, suggestions, methods and / or operational flowcharts of the present disclosure disclosed herein can be applied to various fields requiring wireless communication and / or connection (e.g., 5G) between devices.

[0027] Hereinafter, the present disclosure will be described in more detail with reference to drawings. The same reference numerals in the following drawings and / or descriptions may refer to the same and / or corresponding hardware blocks, software blocks, and / or functional blocks unless otherwise indicated.

[0028] FIG. 1 shows an example of a communication system to which implementations of the present disclosure are applied.

[0029] The 5G usage scenarios shown in FIG. 1 are only exemplary, and the technical features of the present disclosure can be applied to other 5G usage scenarios which are not shown in FIG. 1.

[0030] Three main requirement categories for 5G include (1) a category of enhanced Mobile BroadBand (eMBB), (2) a category of massive Machine Type Communication (mMTC), and (3) a category of Ultra-Reliable and Low Latency Communications (URLLC).

[0031] Referring to FIG. 1, the communication system 1 includes wireless devices 100a to 100f, Base Stations (BSs) 200, and a network 300. Although FIG. 1 illustrates a 5G network as an example of the network of the communication system 1, the implementations of the present disclosure are not limited to the 5G system, and can be applied to the future communication system beyond the 5G system.

[0032] The BSs 200 and the network 300 may be implemented as wireless devices and a specific wireless device may operate as a BS / network node with respect to other wireless devices.

[0033] The wireless devices 100a to 100f represent devices performing communication using Radio Access Technology (RAT) (e.g., 5G NR or LTE) and may be referred to as communication / radio / 5G devices. The wireless devices 100a to 100f may include, without being limited to, a robot 100a, vehicles 100b-1 and 100b-2, an eXtended Reality (XR) device 100c, a hand-held device 100d, a home appliance 100e, an Internet-of-Things (IoT) device 100f, and an Artificial Intelligence (AI) device / server 400. For example, the vehicles may include a vehicle having a wireless communication function, an autonomous driving vehicle, and a vehicle capable of performing communication between vehicles. The vehicles may include an Unmanned Aerial Vehicle (UAV) (e.g., a drone). The XR device may include an Augmented Reality (AR) / Virtual Reality (VR) / Mixed Reality (MR) device and may be implemented in the form of a Head-Mounted Device (HMD), a Head-Up Display (HUD) mounted in a vehicle, a television, a smartphone, a computer, a wearable device, a home appliance device, a digital signage, a vehicle, a robot, etc. The hand-held device may include a smartphone, a smartpad, a wearable device (e.g., a smartwatch or a smartglasses), and a computer (e.g., a notebook). The home appliance may include a TV, a refrigerator, and a washing machine. The IoT device may include a sensor and a smartmeter.

[0034] In the present disclosure, the wireless devices 100a to 100f may be called User Equipments (UEs). A UE may include, for example, a cellular phone, a smartphone, a laptop computer, a digital broadcast terminal, a Personal Digital Assistant (PDA), a Portable Multimedia Player (PMP), a navigation system, a slate Personal Computer (PC), a tablet PC, an ultrabook, a vehicle, a vehicle having an autonomous traveling function, a connected car, an UAV, an AI module, a robot, an AR device, a VR device, an MR device, a hologram device, a public safety device, an MTC device, an IoT device, a medical device, a FinTech device (or a financial device), a security device, a weather / environment device, a device related to a 5G service, or a device related to a fourth industrial revolution field.

[0035] The wireless devices 100a to 100f may be connected to the network 300 via the BSs 200. An AI technology may be applied to the wireless devices 100a to 100f and the wireless devices 100a to 100f may be connected to the AI server 400 via the network 300. The network 300 may be configured using a 3G network, a 4G (e.g., LTE) network, a 5G (e.g., NR) network, and a beyond-5G network. Although the wireless devices 100a to 100f may communicate with each other through the BSs 200 / network 300, the wireless devices 100a to 100f may perform direct communication (e.g., sidelink communication) with each other without passing through the BSs 200 / network 300. For example, the vehicles 100b-1 and 100b-2 may perform direct communication (e.g., Vehicle-to-Vehicle (V2V) / Vehicle-to-everything (V2X) communication). The IoT device (e.g., a sensor) may perform direct communication with other IoT devices (e.g., sensors) or other wireless devices 100a to 100f.

[0036] Wireless communication / connections 150a, 150b and 150c may be established between the wireless devices 100a to 100f and / or between wireless device 100a to 100f and BS 200 and / or between BSs 200. Herein, the wireless communication / connections may be established through various RATs (e.g., 5G NR) such as uplink / downlink communication 150a, sidelink communication (or Device-to-Device (D2D) communication) 150b, inter-base station communication 150c (e.g., relay, Integrated Access and Backhaul (IAB)), etc. The wireless devices 100a to 100f and the BSs 200 / the wireless devices 100a to 100f may transmit / receive radio signals to / from each other through the wireless communication / connections 150a, 150b and 150c. For example, the wireless communication / connections 150a, 150b and 150c may transmit / receive signals through various physical channels. To this end, at least a part of various configuration information configuring processes, various signal processing processes (e.g., channel encoding / decoding, modulation / demodulation, and resource mapping / de-mapping), and resource allocating processes, for transmitting / receiving radio signals, may be performed based on the various proposals of the present disclosure.

[0037] NR supports multiples numerologies (and / or multiple Sub-Carrier Spacings (SCS)) to support various 5G services. For example, if SCS is 15 kHz, wide area can be supported in traditional cellular bands, and if SCS is 30 kHz / 60 kHz, dense-urban, lower latency, and wider carrier bandwidth can be supported. If SCS is 60 kHz or higher, bandwidths greater than 24.25 GHz can be supported to overcome phase noise.

[0038] The NR frequency band may be defined as two types of frequency range, i.e., Frequency Range 1 (FR1) and Frequency Range 2 (FR2). The numerical value of the frequency range may be changed. For example, the frequency ranges of the two types (FR1 and FR2) may be as shown in Table 1 below. For ease of explanation, in the frequency ranges used in the NR system, FR1 may mean "sub 6 GHz range", FR2 may mean "above 6 GHz range," and may be referred to as millimeter Wave (mmW).

[0039] Frequency Range designationCorresponding frequency rangeSubcarrier SpacingFR1450MHz - 6000MHz15, 30, 60kHzFR224250MHz - 52600MHz60, 120, 240kHz

[0040] As mentioned above, the numerical value of the frequency range of the NR system may be changed. For example, FR1 may include a frequency band of 410MHz to 7125MHz as shown in Table 2 below. That is, FR1 may include a frequency band of 6GHz (or 5850, 5900, 5925 MHz, etc.) or more. For example, a frequency band of 6 GHz (or 5850, 5900, 5925 MHz, etc.) or more included in FR1 may include an unlicensed band. Unlicensed bands may be used for a variety of purposes, for example for communication for vehicles (e.g., autonomous driving).

[0041] Frequency Range designationCorresponding frequency rangeSubcarrier SpacingFR1410MHz - 7125MHz15, 30, 60kHzFR224250MHz - 52600MHz60, 120, 240kHz

[0042] Here, the radio communication technologies implemented in the wireless devices in the present disclosure may include NarrowBand IoT (NB-IoT) technology for low-power communication as well as LTE, NR and 6G. For example, NB-IoT technology may be an example of Low Power Wide Area Network (LPWAN) technology, may be implemented in specifications such as LTE Cat NB1 and / or LTE Cat NB2, and may not be limited to the above-mentioned names. Additionally and / or alternatively, the radio communication technologies implemented in the wireless devices in the present disclosure may communicate based on LTE-M technology. For example, LTE-M technology may be an example of LPWAN technology and be called by various names such as enhanced MTC (eMTC). For example, LTE-M technology may be implemented in at least one of the various specifications, such as 1) LTE Cat 0, 2) LTE Cat M1, 3) LTE Cat M2, 4) LTE non-bandwidth limited (non-BL), 5) LTE-MTC, 6) LTE Machine Type Communication, and / or 7) LTE M, and may not be limited to the above-mentioned names. Additionally and / or alternatively, the radio communication technologies implemented in the wireless devices in the present disclosure may include at least one of ZigBee, Bluetooth, and / or LPWAN which take into account low-power communication, and may not be limited to the above-mentioned names. For example, ZigBee technology may generate Personal Area Networks (PANs) associated with small / low-power digital communication based on various specifications such as IEEE 802.15.4 and may be called various names.

[0043] FIG. 2 shows an example of wireless devices to which implementations of the present disclosure are applied.

[0044] In FIG. 2, The first wireless device 100 and / or the second wireless device 200 may be implemented in various forms according to use cases / services. For example, {the first wireless device 100 and the second wireless device 200} may correspond to at least one of {the wireless device 100a to 100f and the BS 200}, {the wireless device 100a to 100f and the wireless device 100a to 100f} and / or {the BS 200 and the BS 200} of FIG. 1. The first wireless device 100 and / or the second wireless device 200 may be configured by various elements, devices / parts, and / or modules.

[0045] The first wireless device 100 may include at least one transceiver, such as a transceiver 106, at least one processing chip, such as a processing chip 101, and / or one or more antennas 108.

[0046] The processing chip 101 may include at least one processor, such a processor 102, and at least one memory, such as a memory 104. Additional and / or alternatively, the memory 104 may be placed outside of the processing chip 101.

[0047] The processor 102 may control the memory 104 and / or the transceiver 106 and may be adapted to implement the descriptions, functions, procedures, suggestions, methods and / or operational flowcharts described in the present disclosure. For example, the processor 102 may process information within the memory 104 to generate first information / signals and then transmit radio signals including the first information / signals through the transceiver 106. The processor 102 may receive radio signals including second information / signals through the transceiver 106 and then store information obtained by processing the second information / signals in the memory 104.

[0048] The memory 104 may be operably connectable to the processor 102. The memory 104 may store various types of information and / or instructions. The memory 104 may store a firmware and / or a software code 105 which implements codes, commands, and / or a set of commands that, when executed by the processor 102, perform the descriptions, functions, procedures, suggestions, methods and / or operational flowcharts disclosed in the present disclosure. For example, the firmware and / or the software code 105 may implement instructions that, when executed by the processor 102, perform the descriptions, functions, procedures, suggestions, methods and / or operational flowcharts disclosed in the present disclosure. For example, the firmware and / or the software code 105 may control the processor 102 to perform one or more protocols. For example, the firmware and / or the software code 105 may control the processor 102 to perform one or more layers of the radio interface protocol.

[0049] Herein, the processor 102 and the memory 104 may be a part of a communication modem / circuit / chip designed to implement RAT (e.g., LTE or NR). The transceiver 106 may be connected to the processor 102 and transmit and / or receive radio signals through one or more antennas 108. Each of the transceiver 106 may include a transmitter and / or a receiver. The transceiver 106 may be interchangeably used with Radio Frequency (RF) unit(s). In the present disclosure, the first wireless device 100 may represent a communication modem / circuit / chip.

[0050] The second wireless device 200 may include at least one transceiver, such as a transceiver 206, at least one processing chip, such as a processing chip 201, and / or one or more antennas 208.

[0051] The processing chip 201 may include at least one processor, such a processor 202, and at least one memory, such as a memory 204. Additional and / or alternatively, the memory 204 may be placed outside of the processing chip 201.

[0052] The processor 202 may control the memory 204 and / or the transceiver 206 and may be adapted to implement the descriptions, functions, procedures, suggestions, methods and / or operational flowcharts described in the present disclosure. For example, the processor 202 may process information within the memory 204 to generate third information / signals and then transmit radio signals including the third information / signals through the transceiver 206. The processor 202 may receive radio signals including fourth information / signals through the transceiver 106 and then store information obtained by processing the fourth information / signals in the memory 204.

[0053] The memory 204 may be operably connectable to the processor 202. The memory 204 may store various types of information and / or instructions. The memory 204 may store a firmware and / or a software code 205 which implements codes, commands, and / or a set of commands that, when executed by the processor 202, perform the descriptions, functions, procedures, suggestions, methods and / or operational flowcharts disclosed in the present disclosure. For example, the firmware and / or the software code 205 may implement instructions that, when executed by the processor 202, perform the descriptions, functions, procedures, suggestions, methods and / or operational flowcharts disclosed in the present disclosure. For example, the firmware and / or the software code 205 may control the processor 202 to perform one or more protocols. For example, the firmware and / or the software code 205 may control the processor 202 to perform one or more layers of the radio interface protocol.

[0054] Herein, the processor 202 and the memory 204 may be a part of a communication modem / circuit / chip designed to implement RAT (e.g., LTE or NR). The transceiver 206 may be connected to the processor 202 and transmit and / or receive radio signals through one or more antennas 208. Each of the transceiver 206 may include a transmitter and / or a receiver. The transceiver 206 may be interchangeably used with RF unit. In the present disclosure, the second wireless device 200 may represent a communication modem / circuit / chip.

[0055] Hereinafter, hardware elements of the wireless devices 100 and 200 will be described more specifically. One or more protocol layers may be implemented by, without being limited to, one or more processors 102 and 202. For example, the one or more processors 102 and 202 may implement one or more layers (e.g., functional layers such as Physical (PHY) layer, Media Access Control (MAC) layer, Radio Link Control (RLC) layer, Packet Data Convergence Protocol (PDCP) layer, Radio Resource Control (RRC) layer, and Service Data Adaptation Protocol (SDAP) layer). The one or more processors 102 and 202 may generate one or more Protocol Data Units (PDUs), one or more Service Data Unit (SDUs), messages, control information, data, or information according to the descriptions, functions, procedures, suggestions, methods and / or operational flowcharts disclosed in the present disclosure. The one or more processors 102 and 202 may generate signals (e.g., baseband signals) including PDUs, SDUs, messages, control information, data, or information according to the descriptions, functions, procedures, suggestions, methods and / or operational flowcharts disclosed in the present disclosure and provide the generated signals to the one or more transceivers 106 and 206. The one or more processors 102 and 202 may receive the signals (e.g., baseband signals) from the one or more transceivers 106 and 206 and acquire the PDUs, SDUs, messages, control information, data, or information according to the descriptions, functions, procedures, suggestions, methods and / or operational flowcharts disclosed in the present disclosure.

[0056] The one or more processors 102 and 202 may be referred to as controllers, microcontrollers, microprocessors, or microcomputers. The one or more processors 102 and 202 may be implemented by hardware, firmware, software, or a combination thereof. As an example, one or more Application Specific Integrated Circuits (ASICs), one or more Digital Signal Processors (DSPs), one or more Digital Signal Processing Devices (DSPDs), one or more Programmable Logic Devices (PLDs), or one or more Field Programmable Gate Arrays (FPGAs) may be included in the one or more processors 102 and 202. For example, the one or more processors 102 and 202 may be configured by a set of a communication control processor, an Application Processor (AP), an Electronic Control Unit (ECU), a Central Processing Unit (CPU), a Graphic Processing Unit (GPU), and a memory control processor.

[0057] The one or more memories 104 and 204 may be connected to the one or more processors 102 and 202 and store various types of data, signals, messages, information, programs, code, instructions, and / or commands. The one or more memories 104 and 204 may be configured by Random Access Memory (RAM), Dynamic RAM (DRAM), Read-Only Memory (ROM), electrically Erasable Programmable Read-Only Memory (EPROM), flash memory, volatile memory, non-volatile memory, hard drive, register, cash memory, computer-readable storage medium, and / or combinations thereof. The one or more memories 104 and 204 may be located at the interior and / or exterior of the one or more processors 102 and 202. The one or more memories 104 and 204 may be connected to the one or more processors 102 and 202 through various technologies such as wired or wireless connection.

[0058] The one or more transceivers 106 and 206 may transmit user data, control information, and / or radio signals / channels, mentioned in the descriptions, functions, procedures, suggestions, methods and / or operational flowcharts disclosed in the present disclosure, to one or more other devices. The one or more transceivers 106 and 206 may receive user data, control information, and / or radio signals / channels, mentioned in the descriptions, functions, procedures, suggestions, methods and / or operational flowcharts disclosed in the present disclosure, from one or more other devices. For example, the one or more transceivers 106 and 206 may be connected to the one or more processors 102 and 202 and transmit and receive radio signals. For example, the one or more processors 102 and 202 may perform control so that the one or more transceivers 106 and 206 may transmit user data, control information, or radio signals to one or more other devices. The one or more processors 102 and 202 may perform control so that the one or more transceivers 106 and 206 may receive user data, control information, or radio signals from one or more other devices.

[0059] The one or more transceivers 106 and 206 may be connected to the one or more antennas 108 and 208. Additionally and / or alternatively, the one or more transceivers 106 and 206 may include one or more antennas 108 and 208. The one or more transceivers 106 and 206 may be adapted to transmit and receive user data, control information, and / or radio signals / channels, mentioned in the descriptions, functions, procedures, suggestions, methods and / or operational flowcharts disclosed in the present disclosure, through the one or more antennas 108 and 208. In the present disclosure, the one or more antennas 108 and 208 may be a plurality of physical antennas or a plurality of logical antennas (e.g., antenna ports).

[0060] The one or more transceivers 106 and 206 may convert received user data, control information, radio signals / channels, etc., from RF band signals into baseband signals in order to process received user data, control information, radio signals / channels, etc., using the one or more processors 102 and 202. The one or more transceivers 106 and 206 may convert the user data, control information, radio signals / channels, etc., processed using the one or more processors 102 and 202 from the base band signals into the RF band signals. To this end, the one or more transceivers 106 and 206 may include (analog) oscillators and / or filters. For example, the one or more transceivers 106 and 206 can up-convert OFDM baseband signals to OFDM signals by their (analog) oscillators and / or filters under the control of the one or more processors 102 and 202 and transmit the up-converted OFDM signals at the carrier frequency. The one or more transceivers 106 and 206 may receive OFDM signals at a carrier frequency and down-convert the OFDM signals into OFDM baseband signals by their (analog) oscillators and / or filters under the control of the one or more processors 102 and 202.

[0061] Although not shown in FIG. 2, the wireless devices 100 and 200 may further include additional components. The additional components 140 may be variously configured according to types of the wireless devices 100 and 200. For example, the additional components 140 may include at least one of a power unit / battery, an Input / Output (I / O) device (e.g., audio I / O port, video I / O port), a driving device, and a computing device. The additional components 140 may be coupled to the one or more processors 102 and 202 via various technologies, such as a wired or wireless connection.

[0062] In the present disclosure, a BS is also referred to as a node B (NB), an eNode B (eNB), or a gNB.

[0063] FIG. 3 shows an example of NG-RAN architecture to which implementations of the present disclosure are applied.

[0064] An NG-RAN node is either:

[0065] - a gNB, providing NR user plane and control plane protocol terminations towards the UE; or

[0066] - an ng-eNB, providing E-UTRA user plane and control plane protocol terminations towards the UE.

[0067] The gNBs and ng-eNBs are interconnected with each other by means of the Xn interface. The gNBs and ng-eNBs are also connected by means of the NG interfaces to the 5GC, more specifically to the Access and Mobility Management Function (AMF) by means of the NG-C interface and to the User Plane Function (UPF) by means of the NG-U interface.

[0068] A Non-Terrestrial Network (NTN) refers to a network, or segment of networks using RF resources on board a satellite (or Unmanned Aerial System (UAS) platform).

[0069] FIG. 4 shows an example of NTN to which implementations of the present disclosure are applied.

[0070] The NTN provides non-terrestrial NR access to the UE by means of an NTN payload and an NTN Gateway. Referring to FIG. 4, a service link between the NTN payload and a UE, and a feeder link between the NTN gateway and the NTN payload are described.

[0071] In FIG. 4, the NTN payload transparently forwards the radio protocol received from the UE (via the service link) to the NTN gateway (via the feeder link) and vice-versa. The following connectivity is supported by the NTN payload:

[0072] - A NTN gateway may serve multiple NTN payloads;

[0073] - An NTN payload may be served by multiple NTN gateways.

[0074] The NTN payload may change the carrier frequency, before re-transmitting it on the service link, and vice versa (respectively on the feeder link).

[0075] For NTN, the following network identities (IDs) are further applied.

[0076] - A Tracking Area (TA) corresponds to a fixed geographical area. Any respective mapping is configured in the RAN;

[0077] - A mapped cell ID.

[0078] Three types of service links are supported:

[0079] - Earth-fixed: provisioned by beam(s) continuously covering the same geographical areas all the time (e.g., the case of Geosynchronous Orbit (GSO) satellites);

[0080] - Quasi-Earth-fixed: provisioned by beam(s) covering one geographic area for a limited period and a different geographic area during another period (e.g., the case of Non-Geosynchronous Orbit (NGSO) satellites generating steerable beams);

[0081] - Earth-moving: provisioned by beam(s) whose coverage area slides over the Earth surface (e.g., the case of NGSO satellites generating fixed or non-steerable beams).

[0082] With NGSO satellites, the gNB may provide either quasi-Earth-fixed service link or Earth-moving service link, while gNB operating with GSO satellite may provide Earth-fixed service link.

[0083] In FIG.4, the transparent NTN payload which may simply act as an RF relay (with some frequency filtering, conversions, and amplifications) was described.

[0084] Meanwhile, NTN capabilities can be enhanced with the regenerative payload architecture on satellite-based gNBs. Unlike transparent payload, the regenerative payload architecture may additionally require a satellite support gNB functions (e.g., modulation / demodulation, encoding / decoding, switching / routing, management of NG / Xn interfaces and UE contexts, RRM, etc.). With shorter delays over Uu interface and much higher performance capability, the regenerative payload architecture aims to further expand the NTN service capabilities and coverages for more advanced use cases.

[0085] FIG. 5 shows another example of NTN to which implementations of the present disclosure are applied.

[0086] Referring to FIG. 5, a satellite (or UAS platform) implements a regeneration of the signals received from Earth (with on board processing). The satellite (or UAS platform) may typically generate several beams over a given service area bounded by its field of view. The footprints of the beams may be typically of elliptic shape. The field of view of the satellite (or UAS platform) may depend on the on board antenna diagram and min elevation angle.

[0087] Regenerative payload means a payload that transforms and amplifies an uplink RF signal before transmitting it on the downlink. The transformation of the signal refers to digital processing that may include radio frequency filtering, frequency conversion and amplification as well as demodulation / decoding, switch and / or routing, coding / modulation. This may be effectively equivalent to having all or part of base station functions (e.g., gNB) on board the satellite (or UAS platform).

[0088] The regenerative payloads may also optionally provide Inter-Satellite Links (ISL) between satellites in case of a constellation of satellites. ISL is a transport link between satellites. ISL may be a radio interface or an optical interface.

[0089] Satellite Radio Interface (SRI) is on the feeder link between the NTN gateway and the satellite. SRI is a transport link between NTN gateway and satellite.

[0090] The NTN gateway is a transport network layer node, and supports all necessary transport protocols.

[0091] FIG. 6 shows another example of NTN to which implementations of the present disclosure are applied.

[0092] Referring to FIG. 6, Xn connection between one or more gNBs on board a satellite may be established via ISL. The gNB on board different satellites may be connected to the same 5G CN on the ground. If the satellite hosts more than one gNB, the same SRI may transport all the corresponding NG interface instances.

[0093] RRC_INACTIVE is a state where a UE remains in CM-CONNECTED and can move within an area configured by NG-RAN (the RAN-based Notification Area (RNA)) without notifying NG-RAN. In RRC_INACTIVE, the last serving gNB node keeps the UE context and the UE-associated NG connection with the serving AMF and UPF.

[0094] If the last serving gNB receives DL data from the UPF or DL UE-associated signaling from the AMF (except the UE Context Release Command message) while the UE is in RRC_INACTIVE, it pages in the cells corresponding to the RNA and may send XnAP RAN Paging to neighbor gNB(s) if the RNA includes cells of neighbor gNB(s).

[0095] Upon receiving the UE Context Release Command message while the UE is in RRC_INACTIVE, the last serving gNB may page in the cells corresponding to the RNA and may send XnAP RAN Paging to neighbor gNB(s) if the RNA includes cells of neighbor gNB(s), in order to release UE explicitly.

[0096] Upon receiving the NG RESET message while the UE is in RRC_INACTIVE, the last serving gNB may page involved UEs in the cells corresponding to the RNA and may send XnAP RAN Paging to neighbor gNB(s) if the RNA includes cells of neighbor gNB(s) in order to explicitly release involved UEs.

[0097] The AMF provides to the NG-RAN node the Core Network Assistance Information to assist the NG-RAN node's decision whether the UE can be sent to RRC_INACTIVE, and to assist UE configuration and paging in RRC_INACTIVE. The Core Network Assistance Information includes the registration area configured for the UE, the Periodic Registration Update timer, and the UE Identity Index value, and may include the UE specific Discontinuous Reception (DRX), an indication if the UE is configured with Mobile Initiated Connection Only (MICO) mode by the AMF, the Expected UE Behavior, the UE Radio Capability for Paging, the Paging Early Indication (PEI) with Paging Subgrouping assistance information, the NR Paging enhanced DRX (eDRX) Information, the Paging Cause Indication for Voice Service and the Hashed UE Identity Index Value.

[0098] The UE registration area is considered by the NG-RAN node when configuring the RNA. The UE specific DRX and UE Identity Index value are used by the NG-RAN node for RAN paging. The Periodic Registration Update timer is considered by the NG-RAN node to configure Periodic RNA Update timer. The NG-RAN node considers the Expected UE Behavior to assist the UE RRC state transition decision. The NG-RAN node may use the UE Radio Capability for Paging during RAN Paging. The NG-RAN node considers the PEI with Paging Subgrouping assistance information for subgroup paging in RRC_INACTIVE except when the UE context contains an emergency PDU session in which case the PEI with Paging Subgrouping assistance information shall not be used. When sending the XnAP RAN Paging to neighbor NG-RAN node(s), the PEI with Paging Subgrouping assistance information may be included. The NG-RAN node considers the NR Paging eDRX Information to configure the RAN Paging when the NR UE is in RRC_INACTIVE. When sending XnAP RAN Paging to neighbor NG-RAN node(s), the NR Paging eDRX Information for RRC_IDLE and for RRC_INACTIVE may be included. The NG-RAN node considers the Paging Cause Indication for Voice Service to include the Paging Cause in RAN Paging for a UE in RRC_INACTIVE state. When sending XnAP RAN Paging to neighbor NG-RAN node(s), the Paging Cause may be included. When sending XnAP RAN Paging to neighbor NG-RAN node(s), the Hashed UE Identity Index Value may be included to determine the start point of PTW.

[0099] At transition to RRC_INACTIVE, the NG-RAN node may configure the UE with a periodic RNA Update timer value.

[0100] If the UE accesses a gNB other than the last serving gNB, the receiving gNB triggers the XnAP Retrieve UE Context procedure to get the UE context from the last serving gNB and may also trigger an Xn-U Address Indication procedure including tunnel information for potential recovery of data from the last serving gNB. Upon successful UE context retrieval, the receiving gNB shall perform the slice-aware admission control in case of receiving slice information and becomes the serving gNB and it further triggers the NGAP Path Switch Request and applicable RRC procedures. After the path switch procedure, the serving gNB triggers release of the UE context at the last serving gNB by means of the XnAP UE Context Release procedure.

[0101] In case the UE is not reachable at the last serving gNB, the gNB shall fail any AMF initiated UE-associated class 1 procedure which allows the signaling of unsuccessful operation in the respective response message. It may trigger the NAS Non Delivery Indication procedure to report the non-delivery of any non PDU Session related NAS PDU received from the AMF.

[0102] If the UE accesses a gNB other than the last serving gNB and the receiving gNB does not find a valid UE Context, the receiving gNB can perform establishment of a new RRC connection instead of resumption of the previous RRC connection. UE context retrieval will also fail and hence a new RRC connection needs to be established if the serving AMF changes.

[0103] A UE in the RRC_INACTIVE state is required to initiate RNA update procedure when it moves out of the configured RNA. When receiving RNA update request from the UE, the receiving gNB triggers the XnAP Retrieve UE Context procedure to get the UE context from the last serving gNB and may decide to send the UE back to RRC_INACTIVE state, move the UE into RRC_CONNECTED state, or send the UE to RRC_IDLE. In case of periodic RNA update, if the last serving gNB decides not to relocate the UE context, it fails the Retrieve UE Context procedure and sends the UE back to RRC_INACTIVE, or to RRC_IDLE directly by an encapsulatedRRCReleasemessage.

[0104] A UE in the RRC_INACTIVE state can be configured by the last serving NG-RAN node with an RNA, where:

[0105] - the RNA can cover a single cell or multiple cells, and shall be contained within the CN registration area, and Xn connectivity should be available within the RNA;

[0106] - a RNA Update (RNAU) is periodically sent by the UE and is also sent when the cell reselection procedure of the UE selects a cell that does not belong to the configured RNA.

[0107] There are several different alternatives on how the RNA can be configured:

[0108] - List of cells: A UE is provided an explicit list of cells (one or more) that constitute the RNA.

[0109] - List of RAN areas: A UE is provided (at least one) RAN area ID, where a RAN area is a subset of a CN Tracking Area or equal to a CN Tracking Area. A RAN area is specified by one RAN area ID, which consists of a TA Code (TAC) and optionally a RAN area Code. A cell broadcasts one or, in case of network sharing with multiple cell ID broadcast, more RAN area IDs in the system information.

[0110] NG-RAN may provide different RNA definitions to different UEs but not mix different definitions to the same UE at the same time. UE shall support all RNA configuration options listed above.

[0111] In the transparent payload architecture, NTN gNBs are on the ground, similar to terrestrial networks. As a result, the change of service link (called "satellite switch", i.e., UE connection switch from one satellite to another satellite), which may be frequent depending on NTN implementations, did not affect the existing network procedure supporting a UE in RRC_INACTIVE state. If a UE moves to RRC_INACTIVE state through one satellite, it may later request resume (or paged by network to do so) through another satellite covering the same area at that moment. These satellites covering the same area and the RNA of a UE at different times may be connected with the same NTN gNB, possibly through different NTN gateways. This scenario is equivalent to the legacy case of a UE resuming with the same gNB. Even if they are connected with different NTN gNBs on the ground, the mobility of a UE in RRC_INACTIVE state between two NTN gNBs (and Xn-connected) could be re-used, allowing the UE context to be relocated from the last serving NTN gNB to the new one.

[0112] On the other hand, in the regenerative payload architecture, the gNB is on-board at satellite, and the UE contexts stored in a gNB for UEs in RRC_INACTIVE state may move as the satellite moves. Even if a UE in RRC_INACTIVE state remains within its RNA, the last serving gNB which is on-board at satellite may leave the RNA. When the UE requests resume to another gNB (e.g., another satellite on-board gNB) serving the RNA at that moment (e.g., due to Mobile Originating (MO)-traffic, paging from gNB), there may have no Xn connection with the last serving satellite on-board gNB storing the UE context. The context retrieval from the last serving satellite on-board gNB would not be successful, and this may lead to releasing the UE (also in the network side), and / or requiring the re-establishment of RRC connection of the UE. The same scenario of the UE resuming on a gNB other than the last serving satellite on-board gNB with no Xn connection may happen due to the actual mobility of the UE outside its RNA or NTN coverage.

[0113] In such a scenario, the last serving satellite on-board gNB (which is about to leave the RNA of the UE) may be configured to wake up the UE to force a resume request so that the UE context can be relocated to a next incoming (and Xn-connected) satellite on-board gNB covering the same area. However, there may be no next immediate incoming satellite in the area. Due to gradual launches of satellites, i.e., all satellites are not deployed simultaneously to form a full constellation but gradually launched over a long scale, there may be coverage gaps. In addition, such frequent serving gNB change may result in the significant signaling load over Uu, just to maintain the UE context and anchor (i.e., serving gNB) point near the RNA of the UE, and requiring constant mobility and path switching procedures in the network side.

[0114] To address the problem described above, a method for optimizing and adapting the legacy Xn-based inactive mobility procedure for the regenerative payload architecture is required, especially when the serving satellite on-board gNB moves outside the RNA of the UE.

[0115] According to implementations of the present disclosure, a new signaling procedure is proposed to support inactive mobility procedure for the regenerative payload architecture in NTN, when there is no Xn connection between the last serving satellite on-board gNB moving outside the RNA of the UE and a receiving gNB.

[0116] The following drawings are created to explain specific embodiments of the present disclosure. The names of the specific devices or the names of the specific signals / messages / fields shown in the drawings are provided by way of example, and thus the technical features of the present disclosure are not limited to the specific names used in the following drawings.

[0117] FIG. 7 shows an example of a method to which implementations of the present disclosure are applied.

[0118] In step S700, the method comprises receiving, by a core network node (e.g., AMF / SMF / UPF), identification information from a first satellite base station (e.g., first satellite on-board gNB) before the first satellite base station leaves an access network-based notification area (e.g., RNA). The access network-based notification area is an area in which an access network-based paging is transmitted to a wireless device in an inactive state.

[0119] In some implementations, the identification information may be used for identifying the first satellite base station when the wireless device resumes a connection via a different base station. For example, the identification information includes at least one of an inactive radio network temporary identity (I-RNTI) value assigned to the wireless device, or an I-RNTI profile of the first satellite base station.

[0120] Additionally and / or alternatively, the first satellite base station may be identified further based on a pre-configuration from an operation administration maintenance (OAM), stored I-RNTI profiles of base stations that the core network node has connections, or mapping between a base station identifier (ID) and I-RNTI that the core network node has stored.

[0121] In some implementations, the method may further comprise receiving verification information from the first satellite base station. The verification information may be used for verifying resumeMAC-I of the wireless device when the wireless device resumes a connection via a different base station. For example, the verification information includes at least one of a source cell RNTI (C-RNTI), a last serving cell physical cell ID (PCI), or KRRC_INT.

[0122] In some implementations, the method may further comprise storing mapping between an I-RNTI value assigned to the wireless device and the first satellite base station.

[0123] In some implementations, the method may further comprise starting buffering of an incoming DL user data and / or DL signaling.

[0124] In step S710, the method comprises receiving, by the core network node, a context retrieval request message from a second base station.

[0125] In some implementations, the context retrieval request message may be received based on at least one of i) no connection between the first satellite base station and the second base station, or ii) unavailability of resolving the first satellite base station from an I-RNTI received from the wireless device.

[0126] In some implementations, the context retrieval request message may include at least one of information related to identification of the first satellite base station and / or UE context of the first satellite base station stored at the core network node, or information related to verification of the wireless device. For example, the information related to identification may include at least one of an I-RNTI value received from the wireless device, or an I-RNTI profile of the first satellite base station obtained previously. For example, the information related to verification of the wireless device may include a resumeMAC-I of the wireless device, or an ID of a cell that the wireless device accessed.

[0127] In step S720, the method comprises identifying, by the core network node, the first satellite base station based on the identification information.

[0128] In some implementations, based on receiving the verification information, the method may further comprise verifying the wireless device based on the verification information.

[0129] In step S730, the method comprises transmitting, by the core network node, a context retrieval response message to the second base station in response to the context retrieval request message.

[0130] In some implementations, the context retrieval response message may include at least one of UE context, or a UL transport network layer (TNL) information for delivery of UL packets from the second base station.

[0131] In some implementations, the method may further comprise transmitting a second context retrieval request message to the first satellite base station, and receiving a second context retrieval response message including UE context from the first satellite base station in response to the second context retrieval request message.

[0132] In some implementations, the method may further comprise receiving the UL packets from the second base station based on the UL TNL information.

[0133] In some implementations, the method may further comprise receiving DL TNL information from the second base station for delivery of DL user data, and transmitting the DL user data to the second base station based on the DL TNL information.

[0134] In some implementations, the method may further comprise releasing UE context in the first satellite base station after obtaining the UE context successfully.

[0135] In some implementations, before receiving the identification information in step S700, the method may further comprise receiving a connection management message from the first satellite base station. The connection management message may include information to be identified by the core network node from identities assigned to wireless devices. The method may further comprise transmitting a connection management response message to the first satellite base station in response to the connection management message. The connection management response message may inform whether the core network node can verify the wireless device or not.

[0136] Furthermore, the method described above in FIG. 7 may be performed by a core network node (e.g., AMF / UPF / SMF).

[0137] The core network node comprises at least one transceiver, at least one processor, and at least one memory operably connectable to the at least one processor and storing instructions that, based on being executed by the at least one processor, perform the method described in FIG. 7.

[0138] More specifically, the core network node (e.g., AMF / SMF / UPF) receives identification information from a first satellite base station (e.g., first satellite on-board gNB) before the first satellite base station leaves an access network-based notification area (e.g., RNA). The access network-based notification area is an area in which an access network-based paging is transmitted to a wireless device in an inactive state.

[0139] In some implementations, the identification information may be used for identifying the first satellite base station when the wireless device resumes a connection via a different base station. For example, the identification information includes at least one of an I-RNTI value assigned to the wireless device, or an I-RNTI profile of the first satellite base station.

[0140] Additionally and / or alternatively, the first satellite base station may be identified further based on a pre-configuration from OAM, stored I-RNTI profiles of base stations that the core network node has connections, or mapping between a base station ID and I-RNTI that the core network node has stored.

[0141] In some implementations, the core network node may receive verification information from the first satellite base station. The verification information may be used for verifying resumeMAC-I of the wireless device when the wireless device resumes a connection via a different base station. For example, the verification information includes at least one of a source C-RNTI, a last serving cell PCI, or KRRC_INT.

[0142] In some implementations, the core network node may store mapping between an I-RNTI value assigned to the wireless device and the first satellite base station.

[0143] In some implementations, the core network node may start buffering of an incoming DL user data and / or DL signaling.

[0144] The core network node receives a context retrieval request message from a second base station.

[0145] In some implementations, the context retrieval request message may be received based on at least one of i) no connection between the first satellite base station and the second base station, or ii) unavailability of resolving the first satellite base station from an I-RNTI received from the wireless device.

[0146] In some implementations, the context retrieval request message may include at least one of information related to identification of the first satellite base station and / or UE context of the first satellite base station stored at the core network node, or information related to verification of the wireless device. For example, the information related to identification may include at least one of an I-RNTI value received from the wireless device, or an I-RNTI profile of the first satellite base station obtained previously. For example, the information related to verification of the wireless device may include a resumeMAC-I of the wireless device, or an ID of a cell that the wireless device accessed.

[0147] The core network node identifies the first satellite base station based on the identification information.

[0148] In some implementations, based on receiving the verification information, the core network node may verify the wireless device based on the verification information.

[0149] The core network node transmits a context retrieval response message to the second base station in response to the context retrieval request message.

[0150] In some implementations, the context retrieval response message may include at least one of UE context, or a UL TNL information for delivery of UL packets from the second base station.

[0151] In some implementations, the core network node may transmit a second context retrieval request message to the first satellite base station, and receive a second context retrieval response message including UE context from the first satellite base station in response to the second context retrieval request message.

[0152] In some implementations, the core network node may receive the UL packets from the second base station based on the UL TNL information.

[0153] In some implementations, the core network node may receive DL TNL information from the second base station for delivery of DL user data, and transmit the DL user data to the second base station based on the DL TNL information.

[0154] In some implementations, the core network node may release UE context in the first satellite base station after obtaining the UE context successfully.

[0155] In some implementations, before receiving the identification information, the core network node may receive a connection management message from the first satellite base station. The connection management message may include information to be identified by the core network node from identities assigned to wireless devices. The core network node may transmit a connection management response message to the first satellite base station in response to the connection management message. The connection management response message may inform whether the core network node can verify the wireless device or not.

[0156] FIG. 8 shows an example of another method to which implementations of the present disclosure are applied.

[0157] In step S800, the method comprises transmitting, by a first satellite base station (e.g., first satellite on-board gNB), identification information to a core network (e.g., AMF / SMF / UPF) before the first satellite base station leaves an access network-based notification area (e.g., RNA). The access network-based notification area is an area in which an access network-based paging is transmitted to a wireless device in an inactive state.

[0158] In some implementations, the identification information may be used for identifying the first satellite base station when the wireless device resumes a connection via a different base station. For example, the identification information includes at least one of an I-RNTI value assigned to the wireless device, or an I-RNTI profile of the first satellite base station.

[0159] In some implementations, the method may further comprise transmitting verification information to the core network. The verification information may be used for verifying resumeMAC-I of the wireless device when the wireless device resumes a connection via a different base station. For example, the verification information includes at least one of a source C-RNTI, a last serving cell PCI, or KRRC_INT.

[0160] Before transmitting the identification information in step S800, the method may further comprise transmitting a connection management message to the core network. The connection management message may include information to be identified by the core network from identities assigned to wireless devices. The method may further comprise receiving a connection management response message from the core network in response to the connection management message. The connection management response message may inform whether the core network can verify the wireless device or not.

[0161] The method may further comprise receiving a second context retrieval request message from the core network, and transmitting a second context retrieval response message including UE context to the core network in response to the second context retrieval request message.

[0162] Furthermore, the method described above in FIG. 8 may be performed by a base station. The base station may be implemented by the second wireless device 200 shown in FIG. 2.

[0163] The base station comprises at least one transceiver, at least one processor, and at least one memory operably connectable to the at least one processor and storing instructions that, based on being executed by the at least one processor, perform the method described in FIG. 8.

[0164] More specifically, the first satellite base station (e.g., first satellite on-board gNB) transmits identification information to a core network (e.g., AMF / SMF / UPF) before the first satellite base station leaves an access network-based notification area (e.g., RNA). The access network-based notification area is an area in which an access network-based paging is transmitted to a wireless device in an inactive state.

[0165] In some implementations, the identification information may be used for identifying the first satellite base station when the wireless device resumes a connection via a different base station. For example, the identification information includes at least one of an I-RNTI value assigned to the wireless device, or an I-RNTI profile of the first satellite base station.

[0166] In some implementations, the first satellite base station may transmit verification information to the core network. The verification information may be used for verifying resumeMAC-I of the wireless device when the wireless device resumes a connection via a different base station. For example, the verification information includes at least one of a source C-RNTI, a last serving cell PCI, or KRRC_INT.

[0167] Before transmitting the identification information, the first satellite base station may transmit a connection management message to the core network. The connection management message may include information to be identified by the core network from identities assigned to wireless devices. The first satellite base station may receive a connection management response message from the core network in response to the connection management message. The connection management response message may inform whether the core network can verify the wireless device or not.

[0168] The first satellite base station may receive a second context retrieval request message from the core network, and transmit a second context retrieval response message including UE context to the core network in response to the second context retrieval request message.

[0169] FIGS. 9 to 11 show an example of a procedure for supporting inactive mobility from a satellite on-board gNB without Xn connection to which implementations of the present disclosure are applied.

[0170] The implementation of the present disclosure described in FIGS. 7 and 8 above may be applied to the implementation of the present disclosure to be described in FIGS. 9 to 11, and vice versa.

[0171] The procedures to be described in FIGS. 9 to 11 may occur at specific instances (or event-based) and / or be executed in a coordinated or unordered manner throughout the overall procedure.

[0172] Operation of FIG. 9 is described first.

[0173] In step S900, the satellite on-board gNB may transmit a connection management message to the 5GC in NG connection management procedure. For example, the satellite on-board gNB may transmit NG Setup Request message or NG-RAN Configuration Update message to the 5GC.

[0174] The connection management message may include information necessary to be identified by the 5GC from the UE identities that the satellite on-board gNB assigns to UEs in active state. Such information may include e.g., I-RNTI profile (i.e., information used to resolve a global NG-RAN node ID from an I-RNTI).

[0175] In step S902, the 5GC may transmit a connection management response message to the satellite on-board gNB in NG connection management procedure. For example, the 5GC may transmit NG Setup Response message or NG-RAN Configuration Update Acknowledge message to the satellite on-board gNB.

[0176] The connection management response message may indicate whether the 5GC can perform the resume MAC-I verification of UEs in inactive state.

[0177] In step S910, the UE is in inactive state (e.g., RRC_INACTIVE state). For example, the UE may receive a release message (e.g.,RRCReleasemessage) with a suspend configuration for transition to the inactive state.

[0178] In step S920, before leaving the RNA of the UE that the satellite on-board gNB has been serving, the serving satellite on-board gNB may provide information to the 5GC. At least one of the followings may be provided to the 5GC.

[0179] - Information necessary for the 5GC to identify the last serving gNB of the UE when the UE resumes through a different gNB: For example, I-RNTI value assigned to the UE, I-RNTI profile of the serving satellite on-board gNB which is used to resolve gNB ID from I-RNTI, etc.;

[0180] - Information necessary to enable the 5GC to perform the resume MAC-I verification of the UE when the UE resumes through a different gNB: For example, RAN UE context including the source C-RNTI, PCI of the last serving cell, KRRC_INT, etc.

[0181] In step S922, the serving satellite on-board gNB may leave the RNA of the UE.

[0182] In step S930, the 5GC may start buffering an incoming DL user data and / or DL signaling upon provisioned the information from the serving satellite on-board gNB.

[0183] Operation of FIG. 10, which may follow the operation of FIG. 9, is described.

[0184] In FIG. 10, a scenario in which a UE requests resume to a gNB other than the last serving satellite on-board gNB with no Xn connection due to the movement of the last serving satellite on-board gNB is described. However, it is only exemplary, and a UE may request resume to a gNB other than the last serving satellite on-board gNB with no Xn connection due to actual movement of the UE outside its RNA or NTN coverage.

[0185] In step S1000, other gNB (i.e., receiving gNB) may enter the RNA of the UE. For example, another satellite on-board gNB may enter the RNA of the UE. For example, TN or NTN gNB may cover the RNA at the moment.

[0186] In step S1010, DL data and / or DL signaling may arrive at the 5GC.

[0187] In step S1012, the 5GC may transmit a paging towards the UE via the receiving gNB.

[0188] In step S1020, the UE may transmit a resume request message (e.g., RRC Resume Request message) to the receiving gNB. For example, the UE may request resume to the receiving gNB due to e.g., MO-traffic or paging received from the network. The resume request message may include at least one of the I-RNTI value assigned by the last serving satellite on-board gNB and the resume MAC-I for verification.

[0189] In step S1030, upon receiving the resume request message from the UE, the receiving gNB may know / decide that there is no Xn connection between the receiving gNB and the last serving satellite on-board gNB (e.g., based on the I-RNTI received from the UE). Additionally and / or alternatively, the receiving gNB may know that it is not able to resolve the gNB ID (e.g., from the I-RNTI received from the UE).

[0190] In step S1040, upon knowing that there is no Xn connection between the receiving gNB and the last serving satellite on-board gNB and / or it is not able to resolve the gNB ID, the receiving gNB may decide to request UE context retrieval to the 5GC. For example, the receiving gNB may transmit a context retrieval request message (e.g., UE Context Retrieval Request message) to the 5GC.

[0191] The context retrieval request message may include at least one of the following information.

[0192] - Information necessary for the 5GC to identify the last serving gNB of the UE and / or information to identify the UE context of the last serving gNB stored at the 5GC: For example, I-RNTI value received from the UE, I-RNTI profile of the last serving gNB that was obtained when there was Xn connection in the past, etc.;

[0193] - Information necessary for verification of the UE: For example, Resume MAC-I, the cell ID that the UE accessed, etc.

[0194] If only the I-RNTI value is provided via the context retrieval request message in step S1040, step S920 in FIG. 9 is mandatory, so that the 5GC can store mapping between I-RNTI of the UE and the last serving gNB of the UE which performed step S920 (i.e., last serving satellite on-board gNB). Based on the mapping, the 5GC can identify the last serving gNB of the UE (i.e., last serving satellite on-board gNB) by the I-RNTI value received from the receiving gNB in step S1040.

[0195] In step S1042, upon receiving the UE context retrieval request from the receiving gNB, the 5GC may identify the last serving gNB of the UE (i.e., last serving satellite on-board gNB). The 5GC may identify the last serving gNB of the UE based on the received I-RNTI value directly, or based on pre-configuration from OAM, or based on the received I-RNTI profile of the last serving gNB of the UE, or based on the stored I-RNTI profiles of gNBs that the 5GC has NG connections so far, or based on the mapping between the gNB ID and I-RNTI that the 5GC has stored.

[0196] In step S1044, once the last serving gNB of the UE is identified / resolved in step S1042, the 5GC may perform, if configured, verification of the UE. For example, if the 5GC has already received the RAN UE context and all information necessary for verification of the UE from the last serving satellite on-board gNB in S920 in FIG. 9, and if the 5GC is configured to verify the resume MAC-I of the UE, then the 5GC may perform the verification of the UE, and may skip the UE context retrieval procedure from the last serving satellite on-board gNB which will be described in FIG. 11.

[0197] Operation of FIG. 11, which may follow the operation of FIG. 9 and / or FIG, 10, is described.

[0198] In step S1100, once the last serving gNB of the UE is identified / resolved in step S1042 in FIG. 10, the 5GC may request retrieval of RAN UE context from the last serving satellite on-board gNB. For example, the 5GC may transmit a context retrieval request message (e.g., UE Context Retrieval Request message) to the last serving satellite on-board gNB. The context retrieval request message may include information necessary for the last serving satellite on-board gNB to identify the UE and verify the UE (e.g., I-RNTI value, Resume MAC-I, the cell ID that the UE accessed, etc.)

[0199] Upon receiving the request of the RAN UE context retrieval from the 5GC, the last serving satellite on-board gNB may identify and / or verify the UE based on the information received from the 5GC. Upon success of the identification and / or verification of the UE, in step S1102, the last serving satellite on-board gNB may reply back with the RAN UE context to the 5GC. For example, the last serving satellite on-board gNB may transmit a context retrieval response message (e.g., UE Context Retrieval Response message) including the RAN UE context to the 5GC.

[0200] Once the UE is successfully verified and the RAN UE context is available, in step S1110, the 5GC may reply back to the receiving gNB. For example, the 5GC may transmit a context retrieval response message (e.g., UE Context Retrieval Response message) to the receiving gNB.

[0201] The context retrieval response message may include the RAN UE context. The context retrieval response message may further include UL NG-U TNL information for delivery of UL packets from the receiving gNB.

[0202] The 5GC may also start forwarding of DL signaling of the UE buffered at the 5GC (if any) to the receiving gNB.

[0203] Upon receiving the context retrieval response message, the receiving gNB may perform admission control based on the information received from the 5GC. Upon successful admission control, the receiving gNB may assign DL NG-U TNL information for delivery of DL packets from the 5GC based on result of the admission control. If Small Data Transmission (SDT) was used, the receiving gNB may start forwarding of UL data or signaling received from the UE to the 5GC. The receiving gNB may decide to fully resume the UE.

[0204] In step S1120, the receiving gNB may transmit the DL NG-U TNL information to the 5GC. Upon receiving the DL NG-U TNL information, the 5GC may start forwarding of DL user data to the receiving gNB.

[0205] Step S1110 and S1120 may be considered as optimization and adaptation of Xn-U address indication and path switch handling of the legacy Xn-based inactive mobility procedure for the inactive mobility procedure from a satellite on-board gNB over NG interface as proposed in the present disclosure. As long as DL data or DL signaling is buffered in the 5GC (in step S930 in FIG. 9) until the UE resumes, there is no need to forwarding data from the last serving satellite on-board gNB to the receiving gNB. Moreover, since context retrieval happens over NG interface, the 5GC can directly switch path to the receiving gNB once the UE context is successfully retrieved and established in the receiving gNB (with admission control). The UL NG-U TNL information (that has been used with the last serving on-board gNB) may be re-used and / or re-assigned for the delivery of UL packets from the receiving gNB, and they may be supplied together in the message that carry the RAN UE context from the 5GC to the receiving gNB (e.g., step S1110). In return, the receiving gNB may provide the DL NG-U TNL information for delivery of DL packets from 5GC (e.g., step S1120), which may be a subset of the UL NG-U TNL information received (based on admission control).

[0206] The UE may be fully resumed from the receiving gNB. In step S1130, the receiving gNB may transmit a resume message (e.g., RRC Resume message) to the UE. In step S1132, the UE may transmit a resume complete message (e.g., RRC Resume Complete message) to the receiving gNB.

[0207] In step S1140, after successfully having the RAN UE context for the inactive mobility of the UE (e.g., received directly from the last serving satellite on-board gNB, or retrieved from the last serving satellite on-board gNB based on the request from the receiving gNB who received the resume request of the UE), the 5GC may further decide to release the UE context in the last serving satellite on-board gNB. For example, the 5GC may transmit a context release message (e.g., UE Context Release message) to the last serving satellite on-board gNB.

[0208] Step S1140 may be executed as soon as the RAN UE context was received from the last serving satellite on-board gNB and stored at the 5GC (i.e., step S920 in FIG. 9), or may be executed after the successful verification and UE context retrieval from the last serving satellite on-board gNB (i.e. right after step S1102).

[0209] The present disclosure may have various advantageous effects.

[0210] For example, the inactive mobility can be enabled to work for the regenerative payload architecture in NTN, when the serving satellite on-board gNB moves outside the RNA of the UE.

[0211] Advantageous effects which can be obtained through specific embodiments of the present disclosure are not limited to the advantageous effects listed above. For example, there may be a variety of technical effects that a person having ordinary skill in the related art can understand and / or derive from the present disclosure. Accordingly, the specific effects of the present disclosure are not limited to those explicitly described herein, but may include various effects that may be understood or derived from the technical features of the present disclosure.

[0212] Claims in the present disclosure can be combined in a various way. For instance, technical features in method claims of the present disclosure can be combined to be implemented or performed in an apparatus, and technical features in apparatus claims can be combined to be implemented or performed in a method. Further, technical features in method claim(s) and apparatus claim(s) can be combined to be implemented or performed in an apparatus. Further, technical features in method claim(s) and apparatus claim(s) can be combined to be implemented or performed in a method. Other implementations are within the scope of the following claims.

Claims

1.A method comprising:receiving, by a core network node, identification information from a first satellite base station before the first satellite base station leaves an access network-based notification area,wherein the access network-based notification area is an area in which an access network-based paging is transmitted to a wireless device in an inactive state;receiving, by the core network node, a context retrieval request message from a second base station;identifying, by the core network node, the first satellite base station based on the identification information; andtransmitting, by the core network node, a context retrieval response message to the second base station in response to the context retrieval request message.2.The method of claim 1, wherein the identification information is for identifying the first satellite base station when the wireless device resumes a connection via a different base station.3.The method of claim 1 or 2, wherein the identification information includes at least one of an inactive radio network temporary identity (I-RNTI) value assigned to the wireless device, or an I-RNTI profile of the first satellite base station.4.The method of claim 3, wherein the first satellite base station is identified further based on at least one of a pre-configuration from an operation administration maintenance (OAM), stored I-RNTI profiles of base stations that the core network node has connections, or mapping between a base station identifier (ID) and I-RNTI that the core network node has stored.5.The method of any claims 1 to 4, wherein the method further comprises receiving verification information from the first satellite base station.6.The method of claim 5, wherein the verification information is for verifying resumeMAC-I of the wireless device when the wireless device resumes a connection via a different base station.7.The method of claim 5 or 6, wherein the verification information includes at least one of a source cell RNTI (C-RNTI), a last serving cell physical cell ID (PCI), or KRRC_INT.8.The method of any claims 5 to 7, wherein the method further comprises verifying the wireless device based on the verification information.9.The method of any claims 1 to 8, wherein the method further comprises storing mapping between an I-RNTI value assigned to the wireless device and the first satellite base station.10.The method of any claims 1 to 9, wherein the method further comprises starting buffering of an incoming downlink (DL) user data and / or DL signaling.11.The method of any claims 1 to 10, wherein the method further comprises receiving a connection management message from the first satellite base station, andwherein the connection management message includes information to be identified by the core network node from identities assigned to wireless devices.12.The method of claim 11, wherein the method further comprises transmitting a connection management response message to the first satellite base station in response to the connection management message, andwherein the connection management response message informs whether the core network node can verify the wireless device or not.13.The method of any claims 1 to 12, wherein the context retrieval request message is received based on at least one of i) no connection between the first satellite base station and the second base station, or ii) unavailability of resolving the first satellite base station from an I-RNTI received from the wireless device.14.The method of any claims 1 to 13, wherein the context retrieval request message includes at least one of information related to identification of the first satellite base station and / or user equipment (UE) context of the first satellite base station stored at the core network node, or information related to verification of the wireless device.15.The method of claim 14, wherein the information related to identification includes at least one of an I-RNTI value received from the wireless device, or an I-RNTI profile of the first satellite base station obtained previously.16.The method of claim 14 or 15, wherein the information related to verification of the wireless device includes a resumeMAC-I of the wireless device, or an ID of a cell that the wireless device accessed.17.The method of any claims 1 to 16, wherein the method further comprises:transmitting a second context retrieval request message to the first satellite base station; andreceiving a second context retrieval response message including UE context from the first satellite base station in response to the second context retrieval request message.18.The method of any claims 1 to 17, wherein the context retrieval response message includes at least one of UE context, or an uplink (UL) transport network layer (TNL) information for delivery of UL packets from the second base station.19.The method of claim 18, wherein the method further comprises receiving the UL packets from the second base station based on the UL TNL information.20.The method of any claims 1 to 19, wherein the method further comprises:receiving DL TNL information from the second base station for delivery of DL user data; andtransmitting the DL user data to the second base station based on the DL TNL information.21.The method of any claims 1 to 20, wherein the method further comprises releasing UE context in the first satellite base station after obtaining the UE context successfully.22.A core network node comprising:at least one transceiver;at least one processor; andat least one memory operably connectable to the at least one processor and storing instructions that, based on being executed by the at least one processor, perform the method of any claims 1 to 21.23.A method comprising:transmitting, by a first satellite base station, identification information to a core network before the first satellite base station leaves an access network-based notification area,wherein the access network-based notification area is an area in which an access network-based paging is transmitted to a wireless device in an inactive state.24.The method of claim 23, wherein the identification information is for identifying the first satellite base station when the wireless device resumes a connection via a different base station.25.The method of claim 23 or 24, wherein the identification information includes at least one of an inactive radio network temporary identity (I-RNTI) value assigned to the wireless device, or an I-RNTI profile of the first satellite base station.26.The method of any claims 23 to 25, wherein the method further comprises transmitting verification information to the core network.27.The method of claim 26, wherein the verification information is for verifying resumeMAC-I of the wireless device when the wireless device resumes a connection via a different base station.28.The method of claim 26 or 27, wherein the verification information includes at least one of a source cell RNTI (C-RNTI), a last serving cell physical cell ID (PCI), or KRRC_INT.29.The method of any claims 23 to 28, wherein the method further comprises transmitting a connection management message to the core network, andwherein the connection management message includes information to be identified by the core network from identities assigned to wireless devices.30.The method of claim 29, wherein the method further comprises receiving a connection management response message from the core network in response to the connection management message, andwherein the connection management response message informs whether the core network can verify the wireless device or not.31.The method of any claims 23 to 30, wherein the method further comprises:receiving a second context retrieval request message from the core network; andtransmitting a second context retrieval response message including user equipment (UE) context to the core network in response to the second context retrieval request message.32.A first satellite base station comprising:at least one transceiver;at least one processor; andat least one memory operably connectable to the at least one processor and storing instructions that, based on being executed by the at least one processor, perform the method of any claims 23 to 31.

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