WO2025173978A1

WO2025173978A1 - Paging for user equipments served by satellite base station

Info

Publication number: WO2025173978A1
Application number: PCT/KR2025/001659
Authority: WO
Inventors: Jaemin HAN; Daewook BYUN; Seokjung KIM
Original assignee: LG Electronics Inc
Current assignee: LG Electronics Inc
Priority date: 2024-02-13
Filing date: 2025-02-05
Publication date: 2025-08-21
Anticipated expiration: 2026-08-13

Abstract

A method and apparatus for paging for User Equipments (UEs) served by a satellite base station is provided. A core network node receives a notification that a first satellite base station leaves access network-based notification area from the first satellite base station, and buffers downlink data and/or downlink signaling based on the notification.

Description

PAGING FOR USER EQUIPMENTS SERVED BY SATELLITE BASE STATION

The present disclosure relates to paging for User Equipments (UEs) served by a satellite base station.

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.

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.

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.

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.

In an aspect, a method is provided. The method comprises receiving, by a core network node, a notification that a first satellite base station leaves an access network-based notification area from the first satellite base station, and buffering, by the core network node, downlink data and/or downlink signaling based on the notification.

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

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

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

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

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

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

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

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

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

FIGS. 9 to 11 show an example of a procedure for efficient RAN paging for UEs in inactive state served by satellite on-board gNBs to which implementations of the present disclosure are applied.

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.

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.

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.

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".

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".

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".

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".

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".

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

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.

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.

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.

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).

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.

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.

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.

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.

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.

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.

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.

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).

Frequency Range designation	Corresponding frequency range	Subcarrier Spacing
FR1	450MHz - 6000MHz	15, 30, 60kHz
FR2	24250MHz - 52600MHz	60, 120, 240kHz

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).

Frequency Range designation	Corresponding frequency range	Subcarrier Spacing
FR1	410MHz - 7125MHz	15, 30, 60kHz
FR2	24250MHz - 52600MHz	60, 120, 240kHz

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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).

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.

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.

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

An NG-RAN node is either:

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

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

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.

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).

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.

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:

- A NTN gateway may serve multiple NTN payloads;

- An NTN payload may be served by multiple NTN gateways.

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

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

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

- A mapped cell ID.

Three types of service links are supported:

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

- 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);

- 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).

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.

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

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.

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.

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).

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.

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.

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

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.

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.

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).

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.

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.

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.

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.

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

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.

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.

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.

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 encapsulated RRCRelease message.

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

- 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;

- 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.

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

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

- 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.

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.

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.

In this case, the legacy RAN paging mechanism could also be re-used since the UE context is stored in the last serving NTN gNB on the ground. Once it receives the incoming DL user data or signaling from 5GC, it may simply request RAN paging to nearby Xn-connected NTN gNBs on the ground (similar to terrestrial networks) whose transparent payloads may be serving the RNA of the UE at that moment.

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 a RAN paging event occurs at the last serving gNB, it is likely that there may be no Xn connection with other gNBs serving the RNA of the UE at that moment. RAN paging may fail, leading to UE context release in the network, and subsequently requiring the UE's RRC connection to be re-established.

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.

To address the problem described above, a method of optimizing and adapting the RAN paging framework for the regenerative payload architecture in NTN is required, especially when the serving satellite on-board gNB moves outside the RNA of the UE.

According to implementations of the present disclosure, before a serving satellite on-board gNB leaves the RNA of a UE in inactive state (e.g., RRC_INACTIVE state), the serving satellite on-board gNB may notify a core network (e.g., core network function/node such as AMF/SMF/UPF), and provide essential information for future RAN paging events. Additionally and/or alternatively, as it leaves the RNA, the serving satellite on-board gNB may forward the UE context to other incoming Xn-connected satellites on-board gNB(s).

According to implementations of the present disclosure, when a RAN paging trigger event occurs at the core network, the core network may transmit a paging request to other gNB(s) serving the RNA of the UE, including necessary detailed information for paging. The receiving gNB(s) may execute Uu paging and/or RAN paging procedures.

According to implementations of the present disclosure, the last serving satellite on-board gNB may notify the core network upon re-entering the RNA. If the UE context is still active with another gNB, the core network may initiate its context release to the last serving on-board gNB.

According to implementations of the present disclosure, the core network may temporarily act as "last serving gNB" for UEs in inactive state for which the last serving satellite on-board gNB leaves the RNA. The problem is caused due to a moving satellite, while the UE and core network on the ground remain still when Mobile-Originating (MO)/Mobile-Terminated (MT) traffic occurs for UEs in inactive state, and therefore, fixing the point of "last serving gNB" to be reachable during the transient period may address the problem.

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.

In step S700, the method comprises receiving, by a core network node (e.g., core network function/node such as AMF/UPF/SMF), a notification that a first satellite base station (e.g., first satellite on-board gNB) leaves an access network-based notification area (e.g., RNA) from the first satellite base station. 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.

In some implementations, the notification may comprise at least one of i) information related to execution of an access network paging (e.g., RAN paging), ii) information related to identify a base station for the access network paging, or iii) information related to time when the first satellite base station covers the access network-based notification area again.

For example, the information related to execution of the access network paging comprises UE context information including at least one of a UE paging identity, the access network-based notification area, or a paging DRX. For example, the information related to identify the base station for the access network paging may comprise at least one of latest user location information, a Cell Global Identity (CGI) of a last serving cell, a last visited Tracking Area Identity (TAI), a list of one or more base stations associated with the access network-based notification area, or a list of one or more base stations to which the first satellite base station forwards UE context information.

In step S710, the method comprises receiving, by the core network node, downlink data and/or downlink signaling.

In step S720, the method comprises buffering, by the core network node, the downlink data and/or downlink signaling based on the notification.

In some implementations, after buffering the downlink data and/or downlink signaling, the method may further comprises transmitting a paging request message to a second base station.

In some implementations, the second base station may be i) a satellite base station, other than the first satellite base station, entering the access network-based notification area, or ii) a TN or NTN base station covering the access network-based notification area. In this case, for example, the paging request message may include at least one of i) information related to execution of a UE paging and an access network paging for the second base station, or ii) information related to whether the second base station performs the access network paging or not.

In some implementations, the second base station may be the first satellite base station re-entering the access network-based notification area. In this case, for example, the method may further comprise receiving a second notification that the first satellite base station re-enters the access network-based notification area from the first satellite base station. For example, the method may further comprise stopping buffering of the downlink data and/or downlink signaling based on at least one of i) the second notification, ii) the first notification including information related to time when the first satellite base station covers the access network-based notification area again, iii) a pre-configuration, or iv) ephemeris information of the first satellite base station. The second notification may correspond to a request for re-establishment or resume of a connection between the first satellite base station and the core network node, based on the connection being suspended or released before the first satellite base station leaves the access network-based notification area. The method may further comprise forwarding the buffered downlink data and/or downlink signaling to the first satellite base station, when the first satellite base station re-enters the access network-based notification area.

In some implementations, the paging request message may correspond to a request for re-establishment or resume of a connection between the first satellite base station and the core network node, based on the connection being suspended or released before the first satellite base station leaves the access network-based notification area. For example, the paging request message may include at least one of i) information related to execution of a UE paging and an access network paging for the first satellite base station, or ii) information related to the re-establishment or resume of the connection and/or UE context.

In some implementations, the method may further comprise transmitting a context release message to the first satellite base station, based on i) the wireless device being served by another base station, ii) UE context in the first satellite base station not having been released.

In some implementations, the method may further comprise, based on no suitable base station being found covering the access network-based notification area again, waiting until the first satellite base stations re-enters the access network-based notification area again, or other base station covers the access network-based notification area. Additionally and/or Alternatively, the method may further comprise, based on no suitable base station being found covering the access network-based notification area again, releasing the wireless device upon expiry of a timer associated with the downlink data and/or downlink signaling.

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

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.

More specifically, the core network node receives a notification that a first satellite base station (e.g., first satellite on-board gNB) leaves an access network-based notification area (e.g., RNA) from the first satellite base station. 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.

For example, the information related to execution of the access network paging comprises UE context information including at least one of a UE paging identity, the access network-based notification area, or a paging DRX. For example, the information related to identify the base station for the access network paging may comprise at least one of latest user location information, a CGI of a last serving cell, a last visited TAI, a list of one or more base stations associated with the access network-based notification area, or a list of one or more base stations to which the first satellite base station forwards UE context information.

The core network node receives downlink data and/or downlink signaling.

The core network node buffers the downlink data and/or downlink signaling based on the notification.

In some implementations, after buffering the downlink data and/or downlink signaling, the core network node may further transmit a paging request message to a second base station.

In some implementations, the second base station may be the first satellite base station re-entering the access network-based notification area. In this case, for example, the core network node may further receive a second notification that the first satellite base station re-enters the access network-based notification area from the first satellite base station. For example, the core network node may further stop buffering of the downlink data and/or downlink signaling based on at least one of i) the second notification, ii) the first notification including information related to time when the first satellite base station covers the access network-based notification area again, iii) a pre-configuration, or iv) ephemeris information of the first satellite base station. The second notification may correspond to a request for re-establishment or resume of a connection between the first satellite base station and the core network node, based on the connection being suspended or released before the first satellite base station leaves the access network-based notification area. The core network node may further forward the buffered downlink data and/or downlink signaling to the first satellite base station, when the first satellite base station re-enters the access network-based notification area.

In some implementations, the core network node may further transmit a context release message to the first satellite base station, based on i) the wireless device being served by another base station, ii) UE context in the first satellite base station not having been released.

In some implementations, based on no suitable base station being found covering the access network-based notification area again, the core network node may further wait until the first satellite base stations re-enters the access network-based notification area again, or other base station covers the access network-based notification area. Additionally and/or Alternatively, based on no suitable base station being found covering the access network-based notification area again, the core network node may further release the wireless device upon expiry of a timer associated with the downlink data and/or downlink signaling.

In step S800, the method comprises transmitting, by a first satellite base station, (e.g., first satellite on-board gNB) a notification that the first satellite base station leaves an access network-based notification area (e.g., RNA) to a core network. 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.

In some implementations, the method may further comprise forwarding UE context information to one or more neighboring satellite on-board gNBs, before leaving the access network-based notification area.

In some implementations, the method may further comprise transmitting a second notification that the first satellite base station re-enters the access network-based notification area to the core network. For example, the second notification may correspond to a request for re-establishment or resume of a connection between the first satellite base station and the core network, based on the connection being suspended or released before the first satellite base station leaves the access network-based notification area.

In some implementations, the method may further comprise receiving a paging request message from the core network. For example, the paging request message may include at least one of i) information related to execution of a UE paging and an access network paging for the first satellite base station, or ii) information related to the re-establishment or resume of the connection and/or UE context.

In some implementations, the method may further comprise receiving downlink data and/or downlink signaling buffered in a core network when the first satellite base station re-enters the access network-based notification area.

In some implementations, the method may further comprise receiving a context release message from the core network, based on i) the wireless device being served by another base station, ii) UE context in the first satellite base station not having been released.

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.

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.

More specifically, the first satellite base station (e.g., first satellite on-board gNB) transmits a notification that the first satellite base station leaves an access network-based notification area (e.g., RNA) to a core network. 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.

In some implementations, the first satellite base station may forward UE context information to one or more neighboring satellite on-board gNBs, before leaving the access network-based notification area.

In some implementations, the first satellite base station may transmit a second notification that the first satellite base station re-enters the access network-based notification area to the core network. For example, the second notification may correspond to a request for re-establishment or resume of a connection between the first satellite base station and the core network, based on the connection being suspended or released before the first satellite base station leaves the access network-based notification area.

In some implementations, the first satellite base station may receive a paging request message from the core network. For example, the paging request message may include at least one of i) information related to execution of a UE paging and an access network paging for the first satellite base station, or ii) information related to the re-establishment or resume of the connection and/or UE context.

In some implementations, the first satellite base station may receive downlink data and/or downlink signaling buffered in a core network when the first satellite base station re-enters the access network-based notification area.

In some implementations, the first satellite base station may receive a context release message from the core network, based on i) the wireless device being served by another base station, ii) UE context in the first satellite base station not having been released.

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.

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.

Operation of FIG. 9 is described first.

In step S900, the UE in connected state (e.g., RRC_CONNECTED state) may receive a release message (e.g., RRCRelease message) with a suspend configuration from the serving satellite on-board gNB. For example, before leaving the RNA of the UE, the serving satellite on-board gNB may determine to move the UE into inactive state (e.g., RRC_INACTIVE state) instead of executing connected mode mobility (e.g. if a UE is dormant or requires power saving, etc.). The release message with the suspend configuration may include I-RNTI and RNA configuration.

Or, the UE was already in inactive state, and the serving satellite on-board gNB is about to leave the RNA of the UE.

In step S910, before leaving the RNA of the UE, the serving satellite on-board gNB may notify the 5GC of leaving the RNA of the UE. Based on the notification from the serving satellite on-board gNB, the 5GC may buffer an incoming DL user data and/or signaling for the UE.

At least one of the following information may be provided to the 5GC together with the notification.

- The information necessary for the 5GC to execute RAN paging: For example, RAN UE context information including UE paging identity, RNA, Paging DRX, etc.;

- The information necessary for the 5GC to identify and pinpoint right gNB(s) covering the RNA of the UE when requesting RAN paging: For example, latest user location information, CGI of last serving cell, last visited TAI, a list of one or more gNBs associated with the current RNA of the UE, a list of one or more gNBs for which the serving satellite on-board gNB has Xn connection and has forwarded the UE context information, etc.;

- The information of when the serving satellite on-board gNB may cover the RNA of the UE again (e.g., timer value).

The 5GC may store the received information, and may use the received information when a RAN paging trigger event occurs for the UE in inactive state.

In step S912, before leaving the RNA of the UE, the serving satellite on-board gNB may also forward the UE context information to the neighboring Xn-connected incoming satellite on-board gNB(s), so that the UE context can be anchored in a satellite on-board gNB serving the RNA of the UE.

In step S920, the serving satellite on-board gNB may leave the RNA of the UE.

In step S930, a RAN paging trigger event (e.g., incoming DL user data and/or DL signaling) may occur at the 5GC for the UE in inactive state.

In step S932, the 5GC may buffer the incoming DL user data and/or DL signaling based on the notification received from the last serving satellite on-board gNB in step S910.

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

In step S1000, another satellite on-board gNB may enter the RNA of the UE. Or, TN or NTN gNB may cover the RNA of the UE at the moment.

In step S1010, the 5GC may transmit a RAN paging request message towards one or more gNBs that is currently serving the RNA of the UE.

The RAN paging request message may include information necessary for the receiving gNB to execute Uu paging and/or RAN paging over Xn interface, e.g., RAN UE context information including UE paging identity, RNA, Paging DRX, etc. The RAN paging request message may further include information related to whether the receiving gNB should perform Xn RAN paging or not (i.e., the 5GC may also explicitly control the receiving gNB on whether to perform XnAP RAN paging or not).

The 5GC may transmit the RAN paging request message towards multiple gNBs. In this case, 5GC may make sure that the paging request is delivered to the gNB of interest only once (via a direct request from the 5GC and/or via XnAP RAN paging from the directly requested gNB).

If there is no suitable gNB found covering the RNA of the UE at the moment, the 5GC may wait until the last serving satellite on-board gNB re-enters the RNA of the UE (in this case, the 5GC may consider the information of when the serving satellite on-board gNB may cover the RNA of the UE again which has been provided in step S910), and/or until other gNB appears and enters the RNA of the UE. Additionally and/or alternatively, the 5GC may release the UE if a timer associated with DL data and/or DL signaling exists and expires before suitable gNB(s) found for RAN paging.

In step S1020, the gNB(s) receiving the RAN paging request message may execute the XnAP RAN paging toward the neighboring Xn-connected gNB(s) serving the RNA of the UE.

In step S1022, the gNB(s) receiving the RAN paging request message may execute Uu paging for the UE.

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

In step S1100, the last serving satellite on-board gNB is about to re-enter the RNA of the UE.

In step S1102, before re-entering the RNA of the UE, the last serving satellite on-board gNB may notify the 5GC. Based on the notification, the 5GC can stop buffering incoming DL user data and/or DL signaling accordingly.

The 5GC may be explicitly aware of the last serving on-board gNB re-entering the RNA of the UE based on the notification received in step S1102.

Additionally and/or alternatively, the 5GC may be implicitly aware of the last serving on-board gNB re-entering the RNA of the UE without the notification received in step S1102. For example, the 5GC may be implicitly aware of the last serving on-board gNB re-entering the RNA of the UE based on at least one of i) the information of when the serving satellite on-board gNB may cover the RNA of the UE again which has been provided in step S910, ii) pre-configuration from Operation Administration Maintenance (OAM), or iii) ephemeris information of the last serving satellite on-board gNB.

In case that the UE NGAP association between the last serving satellite on-board gNB and the 5GC was suspended and/or released before the last serving satellite on-board gNB leaves the RNA of the UE, step S1102 may be used as a request for the 5GC to re-establish and/or resume the UE NGAP association.

In step S1104, in case that the UE category supports a specific class where its DL user data and/or DL signaling can be stored in the 5GC until the last serving satellite on-board gNB re-enters the RNA of the UE, the 5GC may forward buffered (and/or incoming) DL user data and/or DL signaling to the last serving satellite on-board gNB upon re-entering the RNA of the UE. The storing and/or forwarding of the DL user data and/or DL signaling may be handled differently per Quality of Service (QoS) or per class of DL traffic of the UE.

In step S1106, the 5GC may transmit a RAN paging request message to the last serving satellite on-board gNB re-entering the RNA of the UE for DL user data and/or DL signaling buffered at the 5GC. The RAN paging request message may be transmitted in order to re-establish and/or resume the UE NGAP association, in case the UE NGAP association between the last serving satellite on-board gNB and the 5GC was released and/or suspended before the last serving satellite on-board gNB leaves the RNA of the UE. In this case, step S1106 may be used as a request from the 5GC to re-establish and/or resume the UE NGAP association.

The RAN paging request message may include information necessary for the last serving satellite on-board gNB to execute Uu paging and/or RAN paging over Xn interface, e.g., RAN UE context information including UE paging identity, RNA, Paging DRX, etc. The RAN paging request message may further include information necessary to re-establish and/or resume the RAN UE context and/or UE NGAP association.

In step S1108, In case that the UE is currently served by another gNB other than the lase serving satellite on-board gNB (e.g., if paged through another gNB and/or connection has been resumed or re-established while the last serving satellite on-board gNB left the RNA of the UE) and the UE context in the last serving satellite on-board gNB has not been released yet (e.g., due to NG connection temporarily released or suspended), then 5GC may initiate the UE context release to the last serving satellite on-board gNB.

The present disclosure may have various advantageous effects.

For example, the RAN paging for UEs in inactive state (e.g., RRC_INACTIVE state) 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.

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.

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

A method comprising:

receiving, by a core network node, a notification that a first satellite base station leaves an access network-based notification area from the first satellite base station,

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, downlink data and/or downlink signaling; and

buffering, by the core network node, the downlink data and/or downlink signaling based on the notification.
The method of claim 1, wherein the notification comprises at least one of i) information related to execution of an access network paging, ii) information related to identify a base station for the access network paging, or iii) information related to time when the first satellite base station covers the access network-based notification area again.
The method of claim 2, wherein the information related to execution of the access network paging comprises user equipment (UE) context information including at least one of a UE paging identity, the access network-based notification area, or a paging discontinuous reception (DRX).
The method of claim 2 or 3, wherein the information related to identify the base station for the access network paging comprises at least one of latest user location information, a Cell Global Identity (CGI) of a last serving cell, a last visited Tracking Area Identity (TAI), a list of one or more base stations associated with the access network-based notification area, or a list of one or more base stations to which the first satellite base station forwards UE context information.
The method of any claims 1 to 4, wherein the method further comprises, after buffering the downlink data and/or downlink signaling, transmitting a paging request message to a second base station.
The method of claim 5, wherein the second base station is i) a satellite base station, other than the first satellite base station, entering the access network-based notification area, or ii) a terrestrial network (TN) or non-terrestrial network (NTN) base station covering the access network-based notification area.
The method of claim 6, wherein the paging request message includes at least one of i) information related to execution of a UE paging and an access network paging for the second base station, or ii) information related to whether the second base station performs the access network paging or not.
The method of claim 5, wherein the second base station is the first satellite base station re-entering the access network-based notification area.
The method of claim 8, wherein the method further comprises receiving a second notification that the first satellite base station re-enters the access network-based notification area from the first satellite base station.
The method of claim 9, wherein the method further comprises stopping buffering of the downlink data and/or downlink signaling based on at least one of i) the second notification, ii) the first notification including information related to time when the first satellite base station covers the access network-based notification area again, iii) a pre-configuration, or iv) ephemeris information of the first satellite base station.
The method of claim 9 or 10, wherein the second notification corresponds to a request for re-establishment or resume of a connection between the first satellite base station and the core network node, based on the connection being suspended or released before the first satellite base station leaves the access network-based notification area.
The method of any claims 8 to 11, wherein the method further comprises forwarding the downlink data and/or downlink signaling to the first satellite base station, when the first satellite base station re-enters the access network-based notification area.
The method of any claims 8 to 12, wherein the paging request message corresponds to a request for re-establishment or resume of a connection between the first satellite base station and the core network node, based on the connection being suspended or released before the first satellite base station leaves the access network-based notification area.
The method of claim 13, wherein the paging request message includes at least one of i) information related to execution of a UE paging and an access network paging for the first satellite base station, or ii) information related to the re-establishment or resume of the connection and/or UE context.
The method any claims 1 to 14, wherein the method further comprises transmitting a context release message to the first satellite base station, based on i) the wireless device being served by another base station, ii) UE context in the first satellite base station not having been released.
The method any claims 1 to 15, wherein the method further comprises, based on no suitable base station being found covering the access network-based notification area again, waiting until the first satellite base stations re-enters the access network-based notification area again, or other base station covers the access network-based notification area.
The method any claims 1 to 15, wherein the method further comprises, based on no suitable base station being found covering the access network-based notification area again, releasing the wireless device upon expiry of a timer associated with the downlink data and/or downlink signaling.
A core network node comprising:

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 of any claims 1 to 17.
A method comprising:

transmitting, by a first satellite base station, a notification that the first satellite base station leaves an access network-based notification area to a core network,

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.
The method of claim 19, wherein the notification comprises at least one of i) information related to execution of an access network paging, ii) information related to identify a base station for the access network paging, or iii) information related to time when the first satellite base station covers the access network-based notification area again.
The method of claim 20, wherein the information related to execution of the access network paging comprises user equipment (UE) context information including at least one of a UE paging identity, the access network-based notification area, or a paging discontinuous reception (DRX).
The method of claim 20 or 21, wherein the information related to identify the base station for the access network paging comprises at least one of latest user location information, a Cell Global Identity (CGI) of a last serving cell, a last visited Tracking Area Identity (TAI), a list of one or more base stations associated with the access network-based notification area, or a list of one or more base stations to which the first satellite base station forwards UE context information.
The method of any claims 19 to 22, wherein the method further comprises forwarding UE context information to one or more neighboring satellite on-board gNBs, before leaving the access network-based notification area.
The method of any claims 19 to 23, wherein the method further comprises transmitting a second notification that the first satellite base station re-enters the access network-based notification area to the core network.
The method of claim 24, wherein the second notification corresponds to a request for re-establishment or resume of a connection between the first satellite base station and the core network, based on the connection being suspended or released before the first satellite base station leaves the access network-based notification area.
The method of any claims 19 to 25, wherein the method further comprises receiving a paging request message from the core network.
The method of claim 26, wherein the paging request message includes at least one of i) information related to execution of a UE paging and an access network paging for the first satellite base station, or ii) information related to the re-establishment or resume of the connection and/or UE context.
The method of any claims 19 to 27, wherein the method further comprises receiving downlink data and/or downlink signaling buffered in a core network when the first satellite base station re-enters the access network-based notification area.
The method any claims 19 to 28, wherein the method further comprises receiving a context release message from the core network, based on i) the wireless device being served by another base station, ii) UE context in the first satellite base station not having been released.
A first satellite base station comprising:

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 of any claims 19 to 29.