Store-and-forward operations

Abstract

Example embodiments of the present disclosure relate to store-and-forward operations in non-terrestrial networks (NTN). In an aspect, a first non-terrestrial network (NTN) device based on receiving a first registration request from a terminal device and not having a connectivity with a terrestrial network (TN) device, store the first registration request. The first NTN device transmit an identifier assigned to the terminal device to the terminal device. In this way, the registration procedure, authentication procedure, security, and UE subscription data is during store-and-forward scenarios.

Description

STORE-AND-FORWARD OPERATIONSFIELD

[0001] Example embodiments of the present disclosure generally relate to the field of communications, and in particular, to devices, methods, apparatuses and a computer readable storage medium for store-and-forward operations, for example, in non-terrestrial networks (NTN).BACKGROUND

[0002] A communication network can be seen as a facility that enables communications between two or more communication devices, or provides communication devices access to a data network. A mobile or wireless communication network is one example of a communication network. A communication device may be provided with a service by an application server.Such communication networks operate in according with standards such as those provided by 3GPP (Third Generation Partnership Project) or ETSI (European Telecommunications Standards Institute). Examples of standards are the so-called 5G (5th Generation) standards provided by 3 GPPSUMMARY

[0003] In general, example embodiments of the present disclosure provide a solution for store-and-forward operations, for example, in non-terrestrial networks (NTN), especially for handling registration in NTN store-and-forward.

[0004] In a first aspect, there is provided a first non-terrestrial network (NTN) device. The first NTN device comprises at least one processor and at least one memory storing instructions that, when executed by the at least one processor, cause the first NTN device at least to: based on receiving a first registration request from a terminal device and not having a connectivity with a terrestrial network (TN) device, store the first registration request; and transmit, to the terminal device, an identifier assigned to the terminal device.

[0005] In a second aspect, there is provided a terrestrial network (TN) device. The TN device comprises at least one processor and at least one memory storing instructions that, when executed by the at least one processor, cause the TN device at least to: receive, from afirst NTN device, an identifier assigned to a terminal device and a first registration request; and start an authentication for a terminal device using the identifier assigned to the terminal device.

[0006] In a third aspect, there is provided a terminal device. The terminal device comprises at least one processor and at least one memory storing instructions that, when executed by the at least one processor, cause the terminal network device at least to: transmit, to a first NTN device, a first registration request; and receive, from the first NTN device, an identifier assigned to the terminal device in response to the first registration request.

[0007] In a fourth aspect, there is provided a method. The method comprises based on receiving a first registration request from a terminal device and not having a connectivity with a terrestrial network (TN) device, storing the first registration request; and transmitting, to the terminal device, an identifier assigned to the terminal device.

[0008] In a fifth aspect, there is provided a method. The method comprises receiving, from a first NTN device, an identifier assigned to a terminal device and a first registration request; and starting an authentication for a terminal device using the identifier assigned to the terminal device.

[0009] In a sixth aspect, there is provided a method. The method comprises transmitting, to a first NTN device, a first registration request; and receiving, from the first NTN device, an identifier assigned to the terminal device in response to the first registration request.

[0010] In a seventh aspect, there is provided an apparatus. The apparatus comprises means for based on receiving a first registration request from a terminal device and not having a connectivity with a terrestrial network (TN) device, storing the first registration request; and transmitting, to the terminal device, an identifier assigned to the terminal device.

[0011] In an eighth aspect, there is provided an apparatus. The apparatus comprises means for receiving, from a first NTN device, an identifier assigned to a terminal device and a first registration request; and starting an authentication for a terminal device using the identifier assigned to the terminal device.

[0012] In a ninth aspect, there is provided an apparatus. The apparatus comprises means for transmitting, to a first NTN device, a first registration request; and means for receiving, from the first NTN device, an identifier assigned to the terminal device in response to the first registration request.

[0013] In a tenth aspect, there is provided a non-transitory computer readable medium comprising program instructions for causing an apparatus to perform at least the method according to any one of the above third to fourth aspect.

[0014] In an eleventh aspect, there is provided a computer program comprising instructions, which, when executed by an apparatus, cause the apparatus at least to perform at least the method according to any one of the above fourth to sixth aspect.

[0015] In a twelfth aspect, there is provided a first network device. The first network device comprises storing circuitry configured to based on receiving a first registration request from a terminal device and not having a connectivity with a terrestrial network (TN) device, store the first registration request; and transmitting circuitry configured to transmit, to the terminal device, an identifier assigned to the terminal device.

[0016] In a thirteenth aspect, there is provided a second network device. The network device comprises receving circuitry configured to receive, from a first NTN device, an identifier assigned to a terminal device and a first registration request; and starting circuitry configured to start an authentication for a terminal device using the identifier assigned to the terminal device.

[0017] In a fourteenth aspect, there is provided a terminal device. The terminal device comprises transmitting circuitry configured to transmit, to a first NTN device, a first registration request; and receving circuitry configured to receive, from the first NTN device, an identifier assigned to the terminal device in response to the first registration request.

[0018] It is to be understood that the summary section is not intended to identify key or essential features of embodiments of the present disclosure, nor is it intended to be used to limit the scope of the present disclosure. Other features of the present disclosure will become easily comprehensible through the following description.BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Some example embodiments will now be described with reference to the accompanying drawings, in which:

[0020] FIG. 1A illustrates an example of a network environment in which example embodiments of the present disclosure can be implemented;

[0021] FIG. IB illustrates several operation modes associated with embodiments of the present disclosure;

[0022] FIG. 1C illustrates an example of a non-terrestrial network comprising a nonterrestrial network node (e.g., a satellite) and a terrestrial network node during three different time periods;

[0023] FIG. ID illustrates an example of a non-terrestrial network comprising a nonterrestrial network node (e.g., a satellite) and a terrestrial network node during three different time periods;

[0024] FIG. 2 illustrates a process flow of method according to some embodiments of the present disclosure;

[0025] FIG. 3 illustrates a detailed example of interactions between a user equipment and a satellite in accordance with some example embodiments of the present disclosure;

[0026] FIG. 4 illustrates a detailed example of a process flow in accordance with some example embodiments of the present disclosure;

[0027] FIG. 5 illustrates a flowchart of a method performed by an apparatus in accordance with some example embodiments of the present disclosure;

[0028] FIG. 6 illustrates a flowchart of a method performed by an apparatus in accordance with some example embodiments of the present disclosure;

[0029] FIG. 7 illustrates a flowchart of a method performed by an apparatus in accordance with some example embodiments of the present disclosure;

[0030] FIG. 8 illustrates a simplified block diagram of a device that is suitable for implementing some example embodiments of the present disclosure; and

[0031] FIG. 9 illustrates a block diagram of an example of a computer readable medium in accordance with some example embodiments of the present disclosure.

[0032] Throughout the drawings, the same or similar reference numerals represent the same or similar elements.DETAILED DESCRIPTION

[0033] Principles of the present disclosure will now be described with reference to some example embodiments. It is to be understood that these embodiments are described onlyfor the purpose of illustration and help those skilled in the art to understand and implement the present disclosure, without suggesting any limitation as to the scope of the disclosure. The disclosure described herein can be implemented in various manners other than the ones described below.

[0034] In the following description and claims, unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skills in the art to which this disclosure belongs.

[0035] References in the present disclosure to “one embodiment,” “an embodiment,” “an example embodiment,” and the like indicate that the embodiment described may include a particular feature, structure, or characteristic, but it is not necessary that every embodiment includes the particular feature, structure, or characteristic. Moreover, such phrases are not necessarily referring to the same embodiment. Further, when a particular feature, structure, or characteristic is described in connection with an embodiment, it is submitted that it is within the knowledge of one skilled in the art to affect such feature, structure, or characteristic in connection with other embodiments whether or not explicitly described.

[0036] It shall be understood that although the terms “first” and “second” etc. may be used herein to describe various elements, these elements should not be limited by these terms. These terms are only used to distinguish one element from another. For example, a first element could be termed a second element, and similarly, a second element could be termed a first element, without departing from the scope of example embodiments. As used herein, the term “and / or” includes any and all combinations of one or more of the listed terms.

[0037] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of example embodiments. As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises”, “comprising”, “has”, “having”, “includes” and / or “including”, when used herein, specify the presence of stated features, elements, and / or components etc., but do not preclude the presence or addition of one or more other features, elements, components and / or combinations thereof. As used herein, “at least one of the following: ” and “at least one of ” and similar wording, where the list of two or more elements are joined by “and” or “or”, mean at leastany one of the elements, or at least any two or more of the elements, or at least all the elements.

[0038] As used in this application, the term “circuitry” may refer to one or more or all of the following:(a) hardware-only circuits (such as in analog and / or digital circuits) and(b) combinations of hardware circuits and software, such as (as applicable):(i) a combination of analog and / or digital hardware circuit(s) with software (e.g., firmware); and(ii) any portions of hardware processor(s) with software (including digital signal processor(s)), software, and memory(ies) that work together to cause an apparatus, such as a mobile phone or server, to perform various functions) and(c) hardware circuit(s) and or processor(s), such as a microprocessor(s) or a portion of a microprocessor s), that requires software (for example, firmware) for operation, but the software may not be present when it is not needed for operation.

[0039] This definition of circuitry applies to all uses of this term in this application, including in any claims. As a further example, as used in this application, the term circuitry also covers an implementation of merely a hardware circuit or processor (or multiple processors) or portion of a hardware circuit or processor and its (or their) accompanying software and / or firmware. The term circuitry also covers, for example and if applicable to the particular claim element, a baseband integrated circuit or processor integrated circuit for a mobile device or a similar integrated circuit in server, a cellular network device, or other computing or network device.

[0040] As used herein, the term “cellular network” refers to a network operating in accordance with any suitable radio access technology defined by standards, such as Long Term Evolution (LTE), LTE-Advanced (LTE-A), new radio Wideband Code Division Multiple Access (WCDMA), High-Speed Packet Access (HSPA), Narrow Band Internet of Things (NB-IoT) and so on. Furthermore, the communications between a terminal device and a network device of a cellular network may be performed according to any suitable communication protocols, including, but not limited to, the fourth generation (4G), 4.5G, the future fifth generation (5G) communication protocols, and / or any other protocols either currently known or to be developed in the future. Embodiments of the present disclosuremay be applied in various cellular networks. Given the rapid development in communications, there will of course also be future type communication technologies and systems with which the present disclosure may be embodied. It should not be seen as limiting the scope of the present disclosure to only the aforementioned system.

[0041] As used herein, the term “network device” refers to any device in a cellular network via which a terminal device accesses a data network and receives services exposed by other network devices of the cellular network. In some examples, a network device may comprise or implement a network function of a 5thgeneration communication system (5GS) (e.g., a core network) of a cellular network. In some examples, the network devices may be located at the RAN of the 5GS. The network device may be part of a satellite, a base station (BS) or an access point (AP), for example, a node B (NodeB or NB), an evolved NodeB (eNodeB or eNB), a NR NB (also referred to as a gNB), a Remote Radio Unit (RRU), a radio header (RH), a remote radio head (RRH), a relay, a low power node such as a femto, a pico node, and so forth, depending on the applied terminology and technology. A gNB may include a centralized unit CU and one or more distributed DUs. Femto and Pico nodes are small base stations with a small coverage area.

[0042] The term “terminal device” refers to a device of a communication system of a cellular network, such as a 5thgeneration communication system (5GS) that may be capable of wireless (e.g., radio) communication with a NR-RAN of the 5GS). By way of example rather than limitation, a terminal device may also be referred to as a wireless communication device, user equipment (UE), a Subscriber Station (SS), a Portable Subscriber Station, a Mobile Station (MS), or an Access Terminal (AT). Examples of a terminal device include, but not limited to, a mobile phone, a cellular phone, a smart phone, voice over IP (VoIP) phones, wireless local loop phones, a tablet, a wearable terminal device, a personal digital assistant (PDA), portable computers, desktop computer, image capture terminal devices such as digital cameras, gaming terminal devices, music storage and playback appliances, vehiclemounted wireless terminal devices, wireless endpoints, mobile stations, laptop-embedded equipment (LEE), laptop-mounted equipment (LME), USB dongles, smart devices, wireless customer-premises equipment (CPE), an Internet of Things (loT) device, a watch or other wearable, a head-mounted display (HMD), a vehicle, a drone, a medical device and applications (for example, remote surgery), an industrial device and applications (for example, a robot and / or other wireless devices operating in an industrial and / or an automated processing chain contexts), a consumer electronics device, a device operating on commercialand / or industrial wireless networks, and the like. In the following description, the terms “terminal device”, “communication device”, “terminal”, “user equipment” and “UE” may be used interchangeably.

[0043] The store-and-forward (S&F) operation provide communication service for User Equipment (UE) under satellite coverage with intermittent / temporary satellite connectivity (e.g. when the satellite is not connected via a feeder link or via Inter-Satellite Links (ISL) to the ground network) for delay-tolerant communication service. That is it may not be expected that a satellite has simultaneously both the service link (Uu interface to the UE) and (direct or indirect via ISL links) access to the feeder link to the ground network.

[0044] The “store-and-forward (S&F)” service is widely used in the fields of delay-tolerant networking and disruption-tolerant networking. In 3GPP context, a service that could be assimilated to an S&F service is SMS, for which there is no need to have an end-to-end connectivity between the end-points (e.g. an end-point can be a UE and the other an application server) but only between the end-points and the Short Message Service Center (SMSC) which acts as an intermediate node in charge of storing and relying. The support of S&F Satellite operation is suited for the delivery of delay-tolerant / non-real-time loT satellite services with NGSO satellites. Another example of such service is CioT Control Plane data transfer where the 3 GPP network is used to exchange delay tolerant data between a CioT UE reached via the satellite access and applications located on the ground.

[0045] To support S&F Satellite operation for such services, there are several problems to be solved. These include identifying the minimum necessary set of core network elements / network functions that should be placed on board the satellite(s) for the intended service(s); determining how to trigger S&F Satellite operation, and how to execute S&F Satellite operation; identifying necessary enhancements on the related UE and network procedures to support S&F Satellite operation; and determining whether to inform the UE when the S&F Satellite operation is applied; determining how to support Registration procedure during S&F scenarios; determining how to enable Authentication procedure for S&F scenarios; determining how to enable NAS security at UE and Core network; and determining how to ensure UE subscription data retrieval and creation of UE context in RAN.

[0046] In view of the above, example embodiments of the present disclosure provide a solution for store-and-forward operations in non-terrestrial networks (NTN), particularly for handling registration in NTN store-and-forward. In the example embodiments of thepresent disclosure, a first non-terrestrial network (NTN) device may store the first registration request based on receiving a first registration request from a terminal device and not having a connectivity with a terrestrial network (TN) device. The first NTN device may further transmit an identifier assigned to the terminal device to the terminal device. In this way, the registration procedure, authentication procedure, security, and UE subscription data is during store-and-forward scenarios.

[0047] FIG. 1A illustrates an example of a network environment 100a in which example embodiments of the present disclosure can be implemented. The environment 100a may be a part of a communication network and comprise a plurality of terminal devices and network devices, such as a first NTN device 110, TN device 120, and terminal device 130. As an example, the first NTN device 110 may be implemented as a satellite (eNB), nonterrestrial Access and Mobility Function (AMF-NT), or non-terrestrial Radio Access Network (RAN-NT). The TN device 120 may be implemented as a ground station, base station (BS), a terrestrial Access and Mobility Function (AMF-T), and the terminal device 130 may be implemented as a User Equipment (UE) or an Access Terminal (AT). The terminal device 130 may communicate and transmit various data to the first NTN devicel 10 and the TN device 120 via network environment 100a.

[0048] To transmit data and / or control information, the terminal device 130 may perform communications with the first NTN device 110 and TN device 120. A link from the first NTN device 110 and TN device 120 to the terminal device 130 is referred to as a downlink (DL), while a link from the terminal device 130 to the first NTN device 110 and TN device 120 is referred to as an uplink (UL).

[0049] Although the first NTN device 110, TN device 120, and terminal device 130 are described in the communication environment 100a of FIG. 1A, embodiments of the present disclosure may equally apply to any other suitable communication devices in communication with one another. That is, embodiments of the present disclosure are not limited to the exemplary scenarios of FIG. 1 A. In this regard, it is noted that although the terminal device is schematically depicted as a mobile phone and the network device is schematically depicted as a satellite in FIG. 1 A, it is understood that these depictions are exemplary in nature without suggesting any limitation. In other embodiments, the first NTN device 110 and the TN device 120 may be any other communication devices, for example, any other wireless communication devices.

[0050] It is to be understood that the particular number of various communication devices and the particular number of various communication links as shown in FIG. 1A is for illustration purpose only without suggesting any limitations. The communication environment 100a may include any suitable number of communication devices and any suitable number of communication links for implementing embodiments of the present disclosure. In addition, it should be appreciated that there may be various wireless as well as wireline communications (if needed) among all of the communication devices.

[0051] FIG. IB illustrates an example of “normal / default operation” and “S&F Satellite operation” modes 100b associated with the present disclosure. Under “normal or default Satellite operation” mode 100b-l, signalling and data traffic exchange between a terminal device 130 or UE with a first NTN device or satellite 110 access and a TN device or remote ground network 120 requires the service and feeder links to be active simultaneously, so that, at the time that the terminal device 130 interacts over the service link with the satellite, there is a continuous end-to-end connectivity path between the terminal device 130, the first NTN device 110 and the TN device 120. The TN device 120 may then transmit the data received from the terminal device 130 to external network and loT service endpoints 140, such as loT application server.

[0052] Under “S&F Satellite operation” mode 100b-2, the end-to-end exchange of signalling / data traffic is handled as a combination of two steps not concurrent in time. In step 105, signalling / data exchange between the terminal device 130 and the first NTN device 110 takes place, without the first NTN device 110 being simultaneously connected to the TN device 120 (i.e. the first NTN device 110 is able to operate the service link without an active feeder link connection). In step 107, connectivity between the first NTN device 110 and the ground network is established so that communication between the first NTN device 110 and the TN device 120 can take place. So, the first NTN device 110 moves from being connected to the terminal device 130 in step 105 to being connected to the TN device 120 in step 107. The TN device 120 may then transmit the data received from the terminal device 130 to external network and loT service endpoints 140, such as loT application server.

[0053] FIG. 1C shows an example of a non-terrestrial network comprising a non-terrestrial network node (e.g., a satellite) and a terrestrial network node during three different time periods. The non-terrestrial network node (e.g., satellite) comprises a non-terrestrial core network entity 112c and a RAN node 105c (illustrated as RAN 105c), etc. The terrestrialnetwork node is deployed on the ground and includes a terrestrial core network entity 113c, SMF 132c, UPF 134c, PCF 142c, SMSF 136c, DN 138c, UDM 140c.

[0054] In the example shown in FIG. 1C, there are two non-terrestrial network nodes (e.g., two satellites), shown at different times Tl, T2, T3. A first non-terrestrial network node (e.g., a first satellite shown filed in black and solid) includes a first non-terrestrial core network entity (AMF-NT-1) 112c and a first RAN node 105c (shown as RAN 105c). A non-terrestrial network node (e.g., a second satellite shown in white) includes a second nonterrestrial core network entity (AMF-NT-2) 114c and a second RAN node 110c (shown as RAN 110c).

[0055] In the example of FIG. 1C, the first non-terrestrial network node (e.g., the first satellite) has ground station connectivity when located in Rennes (e.g., connectivity with ground station 120c located in Rennes when ground station 120c is within a coverage area of the first non-terrestrial network node) and ground station connectivity when located in Orleans (e.g., connectivity with ground station 124c located in Orleans when ground station 424 is within a coverage area of the first non-terrestrial network node), but no ground station connectivity when crossing (e.g., passing over) Le Mans The second non-terrestrial network node (e.g., the second satellite) has ground station connectivity when located in Rennes (e.g., connectivity with ground station 120c located in Rennes when ground station 120c is within a coverage area of the second non-terrestrial network node) and ground station connectivity when located in Orleans (e.g., connectivity with ground station 124c located in Orleans when ground station 124c is within a coverage area of the second non-terrestrial network node), but no ground station connectivity when crossing (e.g., passing over) Le Mans. For illustration, Tl is between 10.00-10.20 and T2 is between 10.40-11.00.

[0056] At time Tl, the first non-terrestrial network node (e.g., the first satellite) comprising the first non-terrestrial core network entity (AMF-NT-1) 112c and the first RAN node 105c is covering (e.g. located over) Le Mans and the second non-terrestrial network node (e.g., the second satellite) comprising the second non-terrestrial core network entity (AMF-NT-2) 114c and RAN node 110c is providing coverage to Rennes (e.g., is located over Rennes and has ground station connectivity). At T2, the first non-terrestrial network node (e.g., the first satellite shown in black) will be providing coverage to Orleans (e.g., will be located be over and have ground station connectivity) and the second non-terrestrial network node (e.g., the second satellite) will be covering Le Mans. At time T3, the second non-terrestrial networknode (e.g., the second) satellite will have ground station connectivity with Orleans (e.g., will establish connectivity with ground station 124c located in Orleans) and sync up with the terrestrial core network entity (AMF-T) 113c of the terrestrial network node.

[0057] FIG. ID shows an example of a non-terrestrial network comprising a non-terrestrial network node (e.g., a satellite) and a terrestrial network node during three different time periods. The non-terrestrial network node (e.g., satellite) comprises a non-terrestrial core network entity 112d and a RAN node 105d (illustrated as RAN 105d), etc. The terrestrial network node is deployed on the ground and includes a terrestrial core network entity 113d, SGW 132d, PGW 134d, PCRF 142c, SCEF 136c, DN 138c, HSS 140d.

[0058] In the example shown in FIG. ID, there are two non-terrestrial network nodes (e.g., two satellites), shown at different times Tl, T2, T3. A first non-terrestrial network node (e.g., a first satellite shown filed in black and solid) includes a first non-terrestrial core network entity (MME-NT-1) 112d and a first RAN node 105d (shown as RAN 105d). A non-terrestrial network node (e.g., a second satellite shown in white) includes a second nonterrestrial core network entity (MME -NT -2) 114c and a second RAN node 1 lOd (shown as RAN HOd).

[0059] In the example of FIG. ID, the first non-terrestrial network node (e.g., the first satellite) has ground station connectivity when located in Rennes (e.g., connectivity with ground station 120d located in Rennes when ground station 120d is within a coverage area of the first non-terrestrial network node) and ground station connectivity when located in Orleans (e.g., connectivity with ground station 124d located in Orleans when ground station 424 is within a coverage area of the first non-terrestrial network node), but no ground station connectivity when crossing (e.g., passing over) Le Mans The second non-terrestrial network node (e.g., the second satellite) has ground station connectivity when located in Rennes (e.g., connectivity with ground station 120d located in Rennes when ground station 120d is within a coverage area of the second non-terrestrial network node) and ground station connectivity when located in Orleans (e.g., connectivity with ground station 124d located in Orleans when ground station 124d is within a coverage area of the second non-terrestrial network node), but no ground station connectivity when crossing (e.g., passing over) Le Mans. For illustration, Tl is between 10.00-10.20 and T2 is between 10.40-11.00.

[0060] At time Tl, the first non-terrestrial network node (e.g., the first satellite) comprising the first non-terrestrial core network entity (MME -NT-1) 112d and the first RAN node 105dis covering (e.g. located over) Le Mans and the second non-terrestrial network node (e.g., the second satellite) comprising the second non-terrestrial core network entity (MME -NT- 2) 114d and RAN node 1 lOd is providing coverage to Rennes (e.g., is located over Rennes and has ground station connectivity). At T2, the first non-terrestrial network node (e.g., the first satellite shown in black) will be providing coverage to Orleans (e.g., will be located be over and have ground station connectivity) and the second non-terrestrial network node (e.g., the second satellite) will be covering Le Mans. At time T3, the second non-terrestrial network node (e.g., the second) satellite will have ground station connectivity with Orleans (e.g., will establish connectivity with ground station 124d located in Orleans) and sync up with the terrestrial core network entity (AMF-T) 113d of the terrestrial network node.

[0061] FIG. 2 illustrates a process flow of method according to some embodiments of the present disclosure. For the purpose of discussion, the process flow 200 will be described with reference to FIG. 1. It would be appreciated that although the process flow 200 has been described referring to FIG. 1, this process flow 200 may be likewise applied to other similar communication scenarios.

[0062] In the process flow 200, a terminal device 130 (e.g., UE) may transmit (205) a first registration request 202 to a first non-terrestrial network (NTN) device 110. Based on receiving (210) the first registration request 202 from a terminal device and not having a connectivity with a terrestrial network (TN) device 120, the first NTN device 110 may store (215) the first registration request. The first NTN device may further transmit (220) an identifier assigned to the terminal device 204 to the terminal device.

[0063] In some embodiments, the first NTN device may transmit validity time for the identifier assigned to the terminal device to the terminal device 130. In some further examples, the first NTN device may assign the identifier to the terminal device based on an identifier of the first NTN device.

[0064] In some embodiments, when having a connectivity with the TN device 120, the first NTN device may transmit (240) the first registration request and the identifier assigned to the terminal device 130 to the TN device 120. In an embodiment, the first NTN device may also transmit the current location of the terminal device 130 to the TN device 120. This current location may have been determined by a radio access node located on the satellite connecting the terminal device 130 or received from the terminal device 130 either in the registration request or via the radio access node located on the satellite connecting theterminal device 130. When receiving (245) an identifier assigned to a terminal device and a first registration request 206 from the first NTN device and possibly the location information about the terminal device 130, the TN device 120 may start (235) an authentication / identification of the terminal device 130 and stores the identifier assigned to the terminal device and location information about the terminal device 130 received from the first NTN device.

[0065] In some embodiments, the first NTN device 110 may transmit location information of the terminal device with the first registration request and the identifier assigned to the terminal device to the TN device 120.

[0066] In some further embodiments, the TN device 120, as part of the authentication / identification of the terminal device 130, may need to send a NAS request to the terminal device 130. For this purpose the TN device 120 selects instances of the first NTN device 110 that will the first be able to receive the NAS request from the TN device 120 and to communicate the NAS request to the terminal device 130 and provides the NAS request, the identifier assigned to the terminal device and possibly location information related with the terminal device 130 to the instances of the first NTN device 110 it has selected. This / these instance(s) of the first NTN device 110 may thus receive from the TN device 120 a NAS request targeting the terminal device, the identifier assigned to the terminal device and possibly location information related with the terminal device 130 . In some further embodiments, the selected first NTN device 110 may be different NTN device and correspond to a different instance of NTN device that has sent the registration request to the TN device 120. In some examples, the NAS request may correspond to an authentication request. In some other examples, the NAS request may correspond to a security mode command or to a registration response. In some examples, the location information related with the terminal device 130 sent by the TN device 120 to the first NTN device 110 may be derived from the location information received from the first NTN device 110.

[0067] In some examples, the first NTN device 110 may connect to the terminal device by using the identifier of the terminal device and transmit the NAS request targeting the terminal device, to the terminal device 130. The first NTN device 110 may then receive an NAS response from the terminal device 130.

[0068] In some examples, the first NTN device 110 may connect to the terminal device 130 by paging the terminal device using the identifier of the terminal device 130 and possiblythe location information related with the terminal device 130 received from the TN device 120; In some further examples, the first NTN device 110 may connect the terminal device 130 by paging the terminal device 130 using the identifier of the terminal device and the location of the terminal device 130 received from the TN device 120.

[0069] In some example embodiments, when not having connectivity with the TN device, the first NTN device 110 may store the NAS response. When having the connectivity with the TN device 120, the first NTN device 110 may transmit, the NAS response to the TN device 120. .

[0070] In some embodiments, the first NTN device 110 may comprises a third NTN device, and the third NTN device may receive, a NAS message such as an authentication request, a security mode command for the terminal device and the identifier assigned to the terminal device from the TN device 120 and possibly location information corresponding to the device. In some further examples, the first NTN device 1 lOmay be a non-terrestrial access and mobility management function (AMF-NT), and the TN device 120 may be a terrestrial AMF. In some further examples, the first NTN device HOmay be a non-terrestrial Mobility Management Entity (MME), and the TN device 120 is a terrestrial MME.

[0071] In some embodiments, the TN device 120 may start the authentication for the terminal device by selecting a third network device based on a Subscription Permanent Identifier (SUPI or IMSI) or a Subscription Concealed Identifier (SUCI); receiving authentication data from the third network device; and storing the authentication data against the identifier assigned to the terminal device.

[0072] In some embodiments, the TN device 120 may receive location information of the terminal device with the first registration request and the identifier assigned to the terminal device from the first NTN device 110. In some other embodiments, the TN device 120 may transmit, a NAS request targeting the terminal device and the identifier assigned to the terminal device 130 to a second NTN device. In some embodiments, the TN device 120 may transmit a NAS request targeting the terminal device and the identifier assigned to the terminal device and location information associated with the device to a second NTN device. In some embodiments, the TN device 120 may receive NAS response from the second NTN device. In some embodiments, the terminal device 130 may receive, from the first NTN device validity time for the identifier assigned to the terminal device.

[0073] In some embodiments, the terminal device 130 may connect to a second NTNdevice by using the identifier of the terminal device. In some embodiments, the terminal device 130 may receive, from the second NTN device, a NAS request targeting the terminal device. In some embodiments, the terminal device 130 may transmit an NAS response to the second NTN device .

[0074] FIG. 3 illustrates a detailed example of interactions 300 between a user equipment (UE), satellites (eNB) and ground station or gNB in accordance with some example embodiments of the present disclosure. It is noted that FIG. 3 can be deemed as a further example of the process flow 200. For example, the UE 305 may be example devices of the terminal device 130, and the terrestrial AMF (AMT-T) 320 may be the example devices of the TN device 120. It is to be understood that these devices are described only for the purpose of illustration without suggesting any limitation as to the scope of the disclosure. This process will be described in detail as follows.

[0075] As illustrated in FIG. 3, when a non-registered UE 305 connects to a RAN 310-2 located on a store-and-forward satellite in order to start a Mobility Management (MM) procedure (such as registration), it may receive a temporary identifier (GUTI) even though it is not registered yet. The UE 305 being aware via information broadcast over the radio that the radio link corresponds to a S&F satellite does not interpret a radio link failure (closure) as an error (as a failure of the registration attempt), and it may initiate a long time and wait to be paged with this temporary identifier (GUTI).

[0076] When the AMF proxy 310-1 on the S&F satellite transfers the NAS message from the UE 305 (such as, a registration request) to the main AMF-T 320 (on the ground), and it also provides the GUTI and the UE location. In some embodiments, the AMF-T 320 on the ground has received or determined the next NAS message to send to the UE (e.g. authentication challenge from the AUSF), it may determine the most suitable S&F satellite to next contact the UE 305. For example, the AMF-T 320 may determine a S&F satellite with the shortest time as the most suitable S&F satellite, and the shortest time may equal to a summary of time to get a feeder link to this S&F satellite and time for this S&F satellite to have a service link to the UE 305. In some further embodiments, the AMF-T 320 may transfer the next NAS message to send to the UE 305 (e.g. authentication challenge) to the proxy AMF 315-1 on this S&F satellite together with the GUTI currently associated with the UE and the UE location (where to page the UE to send the NAS message). In the present disclosure, proxy AMF refers to AMF-NT. The UE location may also be used by theproxy AMF 315-1 on the S&F satellite to determine when to page the UE (as the S&F satellite may serve on its way around the earth many locations that are different from the location where the UE is to be paged).

[0077] The proxy AMF 315-1 on this S&F satellite, when it determines that it can reach the UE location, may page the UE 305 with the GUTI received from the main AMF 320. The UE 305 may answer to paging request with a service request (that is not NAS secured if NAS security has not yet been settled) and receives the DL NAS message.

[0078] Specifically, according the embodiments of this disclosure, at 302, the UE 305 may transmit an Access Network (AN) message to a Radio Access Network (RAN) 310-2 of a satellite. The AN message may include AN parameters, registration request (Registration type, Subscription Concealed Identifier (SUCI) or 5G-GUTI or PEI). In the scenario of no ground (NG)-RAN, the AN parameters may include, such as, 5G-S- Temporary Mobile Subscriber Identity (TMSI) or Globally Unique AMF Identifier (GUAMI), the selected Public Land Mobile Network (PLMN) ID, Network Slice Selection Assistance Information (NSSAI) information, and Establishment cause.

[0079] The Registration type may indicate if the UE 305 wants to perform an Initial Registration, a Mobility Registration Update, a Periodic Registration Update, an Emergency Registration, a Disaster Roaming Initial Registration, or a Disaster Roaming Mobility Registration Update. When the UE 305 is using E-UTRA, the UE 305 may indicate its support of CIoT 5GS Optimisations, which is relevant for the AMF selection, in the RRC connection establishment signalling associated with the Registration Request.

[0080] The NAS message container shall be included if the UE 305 is sending a Registration Request message as an Initial NAS message and the UE 305 has a valid 5G NAS security context and the UE 305 needs to send non-cleartext IES. If the UE 305 does not need to send non-cleartext IEs, the UE 305 shall send a Registration Request message without including the NAS message container.

[0081] In some examples, if the UE 305 does not have a valid 5G NAS security context, the UE 305 shall send the Registration Request message without including the NAS message container. The UE 305 shall include the entire Registration Request message (i.e. containing cleartext IEs and non-cleartext IEs) in the NAS message container that is sent as part of the Security Mode Complete message.

[0082] In some embodiments, when the UE 305 is performing an Initial Registration (i.e. the UE is in RM-DEREGISTERED state) with a native 5G-GUTI, the UE 305 shall indicate the related GUAMI information in the AN parameters. When the UE is performing an Initial Registration with its SUCI, the UE shall not indicate any GUAMI information in the AN parameters.

[0083] In some example, the (R)AN 310-2 may then transmit an N2 message, including N2 parameters and the Registration Request, to the AMF-NT-1 310-1. For NR satellite access, the AMF-NT-1 310-1 may verify the location of UE 305 and determine whether the PLMN targeted by the UE 305 is allowed to operate at the UE location. If the AMF-NT-1 310-1 does not have connectivity to the ground (e.g., to the AMF-T 320) when receiving the Registration Request, the AMF-NT-1 310-1 stores the Registration Request message.

[0084] At 304, the AMF-NT-1 310-1 may transmit a new NAS message: initial context setup request to the UE 305 via the (R)AN-1 310-2. In some examples, the AMF-NT-1 310-1 may send DL NAS transport with temporary UE identifier (Temp GUTI) to the UE 305. In the context of this disclosure, it is assumed that all the AMF-NT in all satellite in the constellation will have unique different AMF ID. In an embodiment, a non-colliding GUTI allocation is created by using (GUTI = PLMN ID+AMF Region ID+ AMF Set ID+AMF ID+TMSI). In some embodiments, the UE 305 remembers / stores this temporary identifier (Temp GUTI) for future transactions (e.g., for performing actions of the registration procedure). The AMF-NT-1 310-1 may also provide a validity time for this temporary identifier to UE 305.

[0085] At 306, when / if / after the satellite containing RAN-1 310-2 and AMF-NT-1 310-1 moves away from the UE 305 and gets connected to ground station, the AMF-NT-1 310-1 shall share the stored Registration Request message along with the Temp GUTI and UE location to the AMF-T 320 of the ground station.

[0086] At 308, the AMF-T 320 may decide to initiate UE authentication by invoking an AUSF 325. In some embodiments, the AMF-T 320 may select an AUSF based on SUPI or SUCI. For example, if the AMF-T 320 may be configured to support Emergency Registration for unauthenticated SUPIs and the UE 305 indicated Registration type Emergency Registration, the AMF-T 320 may skip the authentication or the AMF-T 320 may accept that the authentication may fail and continue the Registration procedure.

[0087] If an authentication is required, the AMF-T 320 may request the authentication fromthe AUSF 325. At 312-1, upon / after receiving the request from the AMF-T 320, the AUSF 325 may execute the authentication of the UE 305. At 312-2, The AUSF 325 may select a UDM 330 and get the authentication data from the UDM 330.

[0088] At 314, when / if / after the AUSF 325 returns the authentication data to the AMF-T 320, the AMF-T 320 may store it against / with the temp GUTI received from the AMF-NT 310-1 onboard the satellite. The AMF-T 320 may then determine the next probable satellite which can reach the UE location next.

[0089] At 316, the AMF-T 320 may transmit Namf_NlN2Message (containing Authentication Request NAS message and temp GUTI) to an AMF-NT -2 315-1 on a next probable satellite. The AMF-T 320 may also provide the last known location of UE 305. At 318, either the UE 305 comes back after seeing the new cell (RAN-2 315-2) or AMF- NT -2 315-1 pages the UE 305 using the temp GUTI and the UE location. The UE location may also be used by the AMF-NT -2 315-1 on the S&F satellite to determine when to page the UE (as the S&F satellite may serve on its way around the earth many locations that are different from the location where the UE 305 is to be paged). When / after the UE 305 gets connected to the RAN-2 315-2, the RAN-2 315-2 may send an initial UE message (containing a service request). At 322, the AMF-NT -2 315-1 may send the authentication request message to UE received at 318.

[0090] At 324, the UE 305 may send the authentication response message (including HXRES*) to AMF-NT -2 315-1. If the AMF-NT-2 315-1 does not have connectivity to the ground when receiving authentication response message, it will store the authentication response message. At 326, if the AMF-T 320 gets failure response from the AMF-NT-2 315-1, the AMF-T 320 will reattempt with other AMF-NT.

[0091] At 328, when the AMF-NT-2 315-1 comes in contact with ground station (moves away from the UE as well), it may forward the authentication response to the AMF-T 320. At 332, the AMF-T 320 may validate (HXRES *=XRES*) by sending the Authentication Request to the AUSF 325. At 334, the AUSF 325 may send an authentication response with KSEAF to the AMF-T 320.

[0092] At 336, since the NAS security context do not exist, the AMF-T 320 may perform the NAS security initiation by sending Namf_NlN2Message (containing both security mode command for the UE,) and temporary GUTI to the AMF-NT-3 335-1. The AMF-NT-3 335-1 may store the information until reaching the coverage area of the UE 305. In someembodiments, the AMF-T 320 may find the suitable AMF-NT-3 335-1 based on the criteria described at 316. The AMF-T 320 may provide the last known location of UE 305 to the AMF-NT-3 335-1.

[0093] At 338, either the UE 305 comes back after seeing the new cell (RAN-3 335-2) or the AMF-NT-3 335-1 pages the UE 305 using the temp GUTI and the UE location. The UE location may also be used by the AMF-NT-2 315-1 on the S&F satellite to determine when to page the UE (as the S&F satellite may serve on its way around the earth many locations that are different from the location where the UE 305 is to be paged). At 342, the AMF- NT-3 335-1 may try to reach UE 305 via Paging using the temp GUTI or UE 305 tries to establish RRC connection using service request with temp GUTI. Then AMF-NT-3 335-1 may send the NAS security mode command to UE 305. At 344, the UE 305 may enables the security and acknowledges it to AMF-NT-3 335-1.

[0094] At 346, when the AMF-NT-3 335-1 receives security mode command acknowledgement from UE 305, it may store it till regaining the ground station connectivity again. After / When regaining the ground station connectivity, the AMF-NT-3 335-1 sends the stored security mode command acknowledgement to the AMF-T 320. At 348, the AMF-T 320 may determine whether the UE 305 is allowed to be served in S&F scenario or not based on subscription information fetched from the UDM.

[0095] At 352, the AMF-T 320 may then select suitable candidate satellite which is going to serve the UE next. The selection criteria can be as per described at 316. The AMF-T 320 may send the Registration accept message to AMF-NT-4 350-1 via NlN2Message Transfer. The AMF-NT-4 350-1 may store the Registration accept message. The AMF-T 320 may also provide the last known location of UE 305.

[0096] At 354, when / after the AMF-NT-4 350-1 reaches the UE serving area, either the UE 305 comes back after seeing the new cell (RAN-4 350-2) or the AMF-NT-4 350-1 pages the UE 305 using the temp GUTI and the UE location. The UE location may also be used by the AMF-NT-2 315-1 on the S&F satellite to determine when to page the UE (as the S&F satellite may serve on its way around the earth many locations that are different from the location where the UE 305 is to be paged). At 356, the AMF-NT-4 350-1 may send the registration accept and share the TMSI, AS security keys to RAN-4 350-2. At 358, the UE 305 may respond with registration completion towards AMF-NT-4 350-1. The AMF-NT- 4 350-1 will store the registration completion if / when having no ground station connectivity.At 360, the AMF-NT -4 350-1 may forward the registration completion until it reaches the ground connectivity again with AMF-T 320.

[0097] In an embodiment, the UE 305 may support storing temp GUTI (in response to the transmission of the registration request) and use the temp GUTI for performing actions of registration (e.g., responding to Paging or sending any initial NAS request). The AMF-NT may be able to create distinct temp GUTI and have distinct AMF pointer ID for each AMF- NT configured on satellite. In an embodiment, the AMF-NT does not keep any security material (both AS and NAS). Integrity and ciphering are to be done at AMF-T for every NAS message, to keep the AMF-NT as lightweight as possible. The UE is assumed to store the temporary NAS context till the validity time of the temporary GUTI is over (i.e., until temporary GUTI expires).

[0098] FIG. 4 illustrates a detailed example of interactions 400 between a user equipment (UE), satellites, and ground station in accordance with some example embodiments of the present disclosure. It is noted that FIG. 4 can be deemed as a further example of the process flow 200. For example, the UE 405 may be example devices of the terminal device 130, the satellites 410, 415 may be the example devices of the first NTN device 110, and the terrestrial Mobility Management Entity (MME-T) 420 may be the example devices of the TN device 120. It is to be understood that these devices are described only for the purpose of illustration without suggesting any limitation as to the scope of the disclosure. This process may be implemented under Evolved Packet Core (EPC) network and will be described in detail as follows.

[0099] At 402, a UE 402, camping on an E-UTRAN cell, may read the related System Information Broadcast. If the UE 402 can proceed to attach, it initiates the Attach procedure by the transmission, to the eNodeB 410, of an Attach Request (IMSI or old GUTI, Old GUTI type, last visited TAI (if available).

[0100] The RAN-1 410-2 of eNodeB 410 may forward the Attach Request message in a SI -MME control message (Initial UE message). The MME-NT-1 410-1 may verify the UE 405 location and determine whether the PLMN targeted by the UE 305 is allowed to operate at the UE location.

[0101] At 404, if / when the MME-NT-1 410-1 is not in contact with the ground station when receiving message in 402, the MME-NT-1 410-1 may store the attach request message and generate a temporary GUTI and send an NAS clear text message towards UE 405 askingto save the temp GUTI for future NAS transactions. The MME-NT-1 410-1 may also provide the validity time for the temporary GUTI. In some embodiments, the UE 405 may send an acknowledgment for the same.

[0102] At 406, when the MME-NT-1 410-1 regains ground connectivity, it may forward the attach request, IMSI along with the temporary GUTI created for this request at 404 towards MME-T 420. At 408-1 and 408-2, if no UE context for the UE exists at the MME- T 420, if the Attach Request (sent in 402) was not integrity protected, or if the check of the integrity failed, then authentication and NAS security setup to activate integrity protection and NAS ciphering are carried out. The MME-T 420 may get the Authentication Vector (AV) from Home Subscriber Server (HSS) 430.

[0103] At 412-1, the MME-T 420, after getting the authentication key from HSS 430, may try to find the next available satellite that can reach the UE next. For this purpose it selects instances of the MME-NT-2 415-1 that will the first be able to receive a NAS request from the MME-T 420 and to communicate the NAS request (Authentication NAS payload ) to the UE 405 and provides the NAS request (Authentication NAS payload), the temporary identifier assigned to the terminal device and last known location of UE 405 to the instances of the MME-NT-2 415-1 it has selected. When found, it shall create the Authentication NAS payload and forward it to MME-NT-2 (the next available satellite to reach UE). MME- T 420 may also provide the last known location of UE 405.

[0104] At 412-2, when MME-NT-2 415-1 reaches the UE area, it will page the UE 405 using either the IMSI or temp GUTI or both. For this purpose, the UE location received from the MME-T 420 may be used by the MME-NT-4 440-1 on the S&F satellite to determine when to page the UE 405 (as the S&F satellite may serve on its way around the earth many locations that are different from the location where the UE 405 is to be paged). The UE 405 may also reach out to RAN-2 415-2 when seeing the new cell. At 412-3, in both the cases, when the UE 405 gets RRC connected, the MME-NT-2 415-1 may forward the stored Authentication Request message to UE 405. At 414, the UE 405 may respond back with an authentication response towards MME-NT-2 415-1 and the MME-NT-2 415 may store it till it regains ground connection again.

[0105] At 416, if the MME-T 420 gets a failure response from MME-NT-2 415-1, the MME-T 420 will reattempt with other MME-NT. At 418, when MME-NT-2415-1 regains connectivity with the ground station, it may forward the stored Authentication response fromUE to MME-T 420 together with the temp GUTI and the current UE location. At 422, the MME-T 420 may validate the response.

[0106] At 424, if the UE 405 is authenticated by the MME-T 420 successfully, the MME- T 420 may initiate Security mode by selecting the next available satellite which can serve the UE next. For this purpose it selects instances of the MME-NT-3 415-1 that will the first be able to receive a NAS request from the MME-T 420 and to communicate the NAS request (Security mode command) to the UE 405 and provides the NAS request (Security mode command), the temporary identifier assigned to the terminal device and last known location of UE 405 to the instances of the MME-NT-3 415-1 it has selected. . The MME-NT-3 435-1 may store the security mode command until it reaches the UE serving area. At 426, the MME-NT-3 435-1 may transmit a S10 acknowledgement to the MME-T 420.

[0107] At 428-1, when the MME-NT-3 435-1 reaches the UE serving area, it may page the UE using the temp GUTI or IMSI or both. At 428-2, when the UE 405 becomes connected, the MME-NT-3 435-1 will forward the stored security mode command message to UE 405. At 432, once the UE 405 applies the security mode, it may acknowledge the security mode command towards MME-NT-3 435-1. The MME-NT-3 435-1 may store it till it regains the ground connection again. At 434, when the MME-NT-3 435-1 regains ground connectivity it relays the stored security mode acknowledgment message to MME-T 420 with the temporary identifier assigned to the terminal device and last known location of UE 405.

[0108] At 436, after receiving the security mode acknowledgement from MME-NT-3 435- 1, the MME-T 420 may select a Serving Gateway (SGW) 425 and allocate an EPS Bearer Identity for the Default Bearer associated with the UE 405. Then it sends a Create Session Request (IMSI, MSISDN, MME TEID for control plane, PDN GW address, PDN Address, APN) message to the selected Serving GW 425.

[0109] At 438, the Serving GW 425 may create a new entry in its EPS Bearer table and send a Create Session Request (IMSI, MSISDN, APN, Serving GW Address for the user plane, Serving GW TEID of the user plane, Serving GW TEID of the control plane) message to the PDN GW indicated by the PDN GW address received previously. (In this disclosure, SGW+PGW are represented as SAE GW).

[0110] At 442, when the create session is received from SAE-GW, the MME-T 420 may store till it finds the next available satellite to serve the UE next. Once found, the MME-T 420 may send Attach accept along with Create session response information such as userplane address and TEID to MME-NT-4 440-1. The MME-T 420 may also provide the last known location of UE 405.

[0111] At 444-1 and 444-2, the MME-NT-4 440-1 may store the message until it reaches the UE serving area again. For this purpose, the UE location received from the MME-T 420 may also be used by the MME-NT-4 440-1 on the S&F satellite to determine when to page the UE (as the S&F satellite may serve on its way around the earth many locations that are different from the location where the UE 405 is to be paged). When it reaches the UE serving area, it may page the UE 405 using the temporary GUTI, IMSI or both. The UE 405 may also come to connected on its own, when it sees the new cell in new satellite. In either case, when the UE 405 comes to connected state, the MME-NT-4440-1 may forward the message to RAN 440-2 and UE 405. The RAN 440-2 will create its PDN resources based the user plane IP and TEID information. The UE 405 may receive the attach accept, new GUTI along with the PDN information.

[0112] At 446, the UE 405 may acknowledge by sending the Attach complete message to MME-NT-4 440-1. The MME-NT-4440-1 may store it till it regains the ground connectivity. At 448, when the MME-NT-4 440-1 regains the ground connectivity, it may forward the stored Attach complete message to the MME-T 420. After receiving attach complete MME-T 420 may configure the PDN connection by sending Modify bearer Request to SAE- GW 425 by including RAN’s tunnel ID and IP information.

[0113] In the context of this disclosure, it is assumed that the UE may support storing temp GUTI and use it for responding to Paging or while sending any initial NAS request. The MME-NT is able to create distinct temp GUTI and have distinct MME ID for each MME in satellite). The MME-NT are not keeping any security material (both AS and NAS). Integrity and ciphering are to be done at MME-T for every NAS message. This is to keep MME-NT as light weight as possible.

[0114] FIG. 5 illustrates a flowchart of a method 500 performed by an apparatus in accordance with some example embodiments of the present disclosure. For the purpose of discussion, the method 500 will be described from the perspective of the first NTN device 110 with reference to FIG. 1 A.

[0115] At block 502, the first NTN device 110 may store / buffer the first registration request based on / in response to / if / when receiving a first registration request from a terminal device and not having a connectivity with a terrestrial network (TN) device. For example, the firstNTN device may determine receiving the first registration request from the terminal device and not being connected to the TN device, and store / buffer the first registration request based on / in response to the determination. At block 504, the first NTN device may transmit, to the terminal device, an identifier assigned to the terminal device. Note that, the transmission of the identifier may also be based on / in response to the determination of receiving the first registration request from the terminal device and not being connected to the TN device.

[0116] In some embodiments, the first NTN device may transmit, to the terminal device, validity time for the identifier assigned to the terminal device. In some embodiments, the first NTN device may assign the identifier to the terminal device based on an identifier of the first NTN device.

[0117] In some embodiments, the first NTN device may receive location information of the terminal device from the terminal device or from a Radio Network entity (e.g., BS) serving the terminal device.

[0118] In some embodiments, when / if / based on / in response to having the connectivity with the TN device or connecting to the TN device, the first NTN device may transmit, to the TN device, the first registration request and the identifier assigned to the terminal device. For example, the first NTN device may determine having the connectivity with the TN device or connecting to the TN device, and transmit the stored / buffered the first registration request and the identifier assigned to the terminal device to the TN device based on / in response to the determination. In some embodiments, the first NTN device may transmit, to the TN device, the location information of the terminal device with the first registration request and the identifier assigned to the terminal device (based on / in response to the determination of having the connectivity with the TN device or connecting to the TN device).

[0119] In some embodiments, the first NTN device may receive, from the TN device, a NAS request targeting the terminal device and the identifier assigned to the terminal device. In some embodiments, the first NTN device receiving the NAS request from the TN device may be different from the first NTN device transmitting the registration request and the identifier assigned to the terminal device (e.g., AMF-NT-1 and AMF-NT-2).

[0120] In some embodiments, the first NTN device may connect to the terminal device by using the identifier of the terminal device; transmit, to the terminal device, the NAS request targeting the terminal device; and receive, from the terminal device, an NAS response.

[0121] In some embodiments, the first NTN device may connect to the terminal device by paging the terminal device using the identifier of the terminal device. In some embodiments, the first NTN device may connect the terminal device by paging the terminal device using the identifier of the terminal device and the location of the terminal device.

[0122] In some embodiments, when not having connectivity with the TN device, the first NTN device may store the NAS response; and in some embodiments, when having the connectivity with the TN device, the first NTN device may transmit, to the TN device, the NAS response. In some embodiments, the NTN device correspond to a different instance of NTN device than the described above.

[0123] In some embodiments, the first NTN device may receive, from the TN device, an authentication request, a security mode command for the terminal device and the identifier assigned to the terminal device. In some embodiments, the first NTN device may be an AMF-NT; and in some embodiments, the TN device is a terrestrial AMF.

[0124] In some embodiments, the first NTN device is non-terrestrial Mobility Management Entity (MME); and in some embodiments, the TN device is a terrestrial MME.

[0125] FIG. 6 illustrates a flowchart of a method 600 performed by an apparatus in accordance with some example embodiments of the present disclosure. For the purpose of discussion, the method 600 will be described from the perspective of the TN device 120 with reference to FIG. 1A.

[0126] At block 602, the TN device 120 may receive, from a first non-terrestrial network (NTN) device, an identifier assigned to a terminal device and a first registration request (of / for the terminal device). At block 604, the TN device 120 may start an authentication for the terminal device using the identifier assigned to the terminal device.

[0127] In some embodiments, the TN device 120 may start the authentication for the terminal device by selecting a third network device based on a Subscription Permanent Identifier (SUPI or IMSI) or a Subscription Concealed Identifier (SUCI); receiving authentication data from the third network device; and storing the authentication data against the identifier assigned to the terminal device. In some embodiments, the TN device 120 may receive location information of the terminal device with the first registration request and the identifier assigned to the terminal device from the first NTN device.

[0128] In some embodiments, the TN device 120 may transmit, to a second NTN device, aNAS request targeting the terminal device and the identifier assigned to the terminal device. In some further embodiments, the TN device 120 may transmit, a NAS request targeting the terminal device and the identifier assigned to the terminal device and location information associated with the device to a second NTN device. In some embodiments, the TN device 120 may receive a NAS response from the second NTN device. In some other examples, the first NTN device and the second NTN device may be a non-terrestrial access and mobility management function (AMF-NT) and the TN device may be a terrestrial AMF. In some other examples, the first NTN device may be a non-terrestrial Mobility Management Entity (MME), and the TN device may be a terrestrial MME.

[0129] Note that the TN device 120 may determine the next NTN device (or the device on which the NTN device is configured) able to contact the terminal device as the second NTN device. In some embodiments, the first NTN device and the second NTN device may be (configured on) the same NTN device. For example, the first NTN device and the second NTN device may be configured on the same satellite. In some embodiments, the first NTN device and the second NTN device are different NTN devices (e.g., AMF-NT-1 and AMF- NT-2) (e g., MME-NT-1 and MME-NT-2).

[0130] FIG. 7 illustrates a flowchart of a method 700 performed by an apparatus in accordance with some example embodiments of the present disclosure. For the purpose of discussion, the method 700 will be described from the perspective of the terminal device 130 with reference to FIG. 1 A.

[0131] At block 702, the terminal device 130 may transmit, to a first non-terrestrial network (NTN) device, a first registration request. At 704, the terminal device may receive, from the first NTN device, an identifier assigned to the terminal device 130 in response to the first registration request.

[0132] In some embodiments, the terminal device may receive, from the first NTN device validity time for the identifier assigned to the terminal device.

[0133] In an embodiment, the terminal device 130 performs the subsequent registration procedure / actions (by) using the identifier received in response to the first registration request. For example, the terminal device 130 may connect to a second NTN device (by) using the identifier assigned to the terminal device. As an alternative or in addition, the terminal device 130 may be paged by a second NTN device device (by) using the identifier assigned to the terminal device, to perform the subsequent registration procedure / actions.

[0134] In some embodiments, the terminal device may connect to a second NTN device by using the identifier of the terminal device (e.g., the second NTN device may page the terminal device (by) using the identifier assigned to the terminal device in response to the first registration request). The terminal device may receive, from the second NTN device, a NAS request targeting the terminal device. The terminal device may transmit an NAS response to the second NTN device.

[0135] In some embodiments, the first NTN device and the second NTN device may be (configured on) the same NTN device. For example, the first NTN device and the second NTN device may be configured on the same satellite. In some embodiments, the first NTN device and the second NTN device are different NTN devices (e.g., AMF-NT-1 and AMF- NT-2).

[0136] In some embodiments, an apparatus capable of performing any of the method 500 may be part of a first NTN device 110 and may comprise means for performing the respective operations of the method 500. The means may be implemented in any suitable form. For example, the means may be implemented in a circuitry or software module.

[0137] In some embodiments, the apparatus comprises means for based on receiving a first registration request from a terminal device and not having a connectivity with a terrestrial network (TN) device, storing the first registration request. In some embodiments, the apparatus comprises means for transmitting, to the terminal device, an identifier assigned to the terminal device.

[0138] In some embodiments, the apparatus comprises means for transmitting, to the terminal device, validity time for the identifier assigned to the terminal device. In some embodiments, the apparatus comprises means for assigning the identifier to the terminal device based on an identifier of the first NTN device.

[0139] In some embodiments, the apparatus comprises means for when having the connectivity with the TN device, transmitting, to the TN device, the first registration request and the identifier assigned to the terminal device. In some embodiments, the apparatus comprises means for transmitting, to the TN device, location information of the terminal device with the first registration request and the identifier assigned to the terminal device.

[0140] In some embodiments, the apparatus comprises means for receiving, from the TN device, a non-access stratum (NAS) request targeting the terminal device and the identifierassigned to the terminal device.

[0141] In some embodiments, the apparatus comprises means for connecting to the terminal device by using the identifier of the terminal device; transmit, to the terminal device, the NAS request targeting the terminal device; and receive, from the terminal device, an NAS response.

[0142] In some embodiments, the apparatus comprises means for connecting to the terminal device by paging the terminal device using the identifier of the terminal device. In some embodiments, the apparatus comprises means for connecting the terminal device by paging the terminal device using the identifier of the terminal device and the location of the terminal device.

[0143] In some embodiments, the apparatus comprises means for when not having connectivity with the TN device, storing the NAS response; and in some embodiments, when having the connectivity with the TN device, the first NTN device may transmit, to the TN device, the NAS response. In some embodiments, the apparatus comprises means for the NTN device correspond to a different instance of NTN device than the described above.

[0144] In some embodiments, the apparatus comprises means for first NTN device being an non-terrestrial access and mobility management function (AMF-NT); and In some embodiments, the apparatus comprises means for the TN device being a terrestrial AMF.

[0145] In some embodiments, the apparatus comprises means for the first NTN device being non-terrestrial Mobility Management Entity (MME); and in some embodiments, the TN device being a terrestrial MME.

[0146] In some embodiments, the apparatus further comprises means for performing other steps in some embodiments of the method 500. In some embodiments, the means comprises at least one processor and at least one memory including computer program code, the at least one memory and computer program code configured to, with the at least one processor, cause the performance of the apparatus.

[0147] In some embodiments, an apparatus capable of performing any of the method 600 may be part of a NT device 120 and may comprise means for performing the respective operations of the method 600. The means may be implemented in any suitable form. For example, the means may be implemented in a circuitry or software module.

[0148] In some embodiments, the apparatus comprises means for receiving, from a firstnon-terrestrial network (NTN) device, an identifier assigned to a terminal device and a first registration request. In some embodiments, the apparatus comprises means for starting an authentication for a terminal device using the identifier assigned to the terminal device.

[0149] In some embodiments, the apparatus comprises means for starting the authentication for the terminal device by selecting a third network device based on a Subscription Permanent Identifier (SUPI or IMSI) or a Subscription Concealed Identifier (SUCI); means for receiving authentication data from the third network device; and storing the authentication data against the identifier assigned to the terminal device.

[0150] In some embodiments, the apparatus comprises means for receiving, from the first NTN device, location information of the terminal device with the first registration request and the identifier assigned to the terminal device

[0151] In some embodiments, the apparatus comprises means for transmitting, to a second NTN device, a NAS request targeting the terminal device and the identifier assigned to the terminal device. In some embodiments, the apparatus comprises means for transmitting, to a second NTN device, a NAS request targeting the terminal device and the identifier assigned to the terminal device and location information associated with the device. In some embodiments, the apparatus comprises means for receiving a NAS response from the second NTN device.

[0152] In some embodiments, the apparatus comprises means for the first NTN device being a non-terrestrial access and mobility management function (AMF-NT) and the TN device being a terrestrial AMF. In some embodiments, the apparatus comprises means for the first NTN device is a non-terrestrial Mobility Management Entity (MME), and means for the TN device being a terrestrial MME.

[0153] In some embodiments, the apparatus further comprises means for performing other steps in some embodiments of the method 600. In some embodiments, the means comprises at least one processor and at least one memory including computer program code, the at least one memory and computer program code configured to, with the at least one processor, cause the performance of the apparatus.

[0154] In some embodiments, an apparatus capable of performing any of the method 700 may be part of a terminal device 130 and may comprise means for performing the respective operations of the method 700. The means may be implemented in any suitable form. Forexample, the means may be implemented in a circuitry or software module.

[0155] In some embodiments, the apparatus further comprises means for transmitting, to a first non-terrestrial network (NTN) device, a first registration request. In some embodiments, the apparatus further comprises means for receiving, from the first NTN device, an identifier assigned to the terminal device in response to the first registration request.

[0156] In some embodiments, the apparatus further comprises means for receiving, from the first NTN device, validity time for the identifier assigned to the terminal device. In some embodiments, the apparatus further comprises means for connecting to a second NTN device by using the identifier of the terminal device; means for receiving, from the second NTN device, a NAS request targeting the terminal device; and means for transmitting, to the second NTN device, an NAS response.

[0157] In some embodiments, the apparatus further comprises means for performing other steps in some embodiments of the method 700. In some embodiments, the means comprises at least one processor and at least one memory including computer program code, the at least one memory and computer program code configured to, with the at least one processor, cause the performance of the apparatus.

[0158] FIG. 8 illustrates a simplified block diagram of a device 800 that is suitable for implementing some example embodiments of the present disclosure. The device 800 may be provided to implement a communication device, for example, the terminal device 130 and the network devices 110, 120 as shown in FIG. 1. As shown, the device 800 includes one or more processors 810, one or more memories 820 coupled to the processor 810, and one or more communication modules 840 coupled to the processor 810.

[0159] The communication module 840 is for bidirectional communications. The communication module 840 has at least one antenna to facilitate communication. The communication interface may represent any interface that is necessary for communication with other network elements.

[0160] The processor 810 may be of any type suitable to the local technical network and may include one or more of the following: general purpose computers, special purpose computers, microprocessors, digital signal processors (DSPs) and processors based on multicore processor architecture, as non-limiting examples. The device 800 may havemultiple processors, such as an application specific integrated circuit chip that is slaved in time to a clock which synchronizes the main processor.

[0161] The memory 820 may include one or more non-volatile memories and one or more volatile memories. Examples of the non-volatile memories include, but are not limited to, a Read Only Memory (ROM) 824, an electrically programmable read only memory (EPROM), a flash memory, a hard disk, a compact disc (CD), a digital video disk (DVD), and other magnetic storage and / or optical storage. Examples of the volatile memories include, but are not limited to, a random access memory (RAM) 822 and other volatile memories that will not last in the power-down duration.

[0162] A computer program 830 includes computer executable instructions that are executed by the associated processor 810. The program 830 may be stored in the ROM 824. The processor 810 may perform any suitable actions and processing by loading the program 830 into the RAM 822.

[0163] The embodiments of the present disclosure may be implemented by means of the program 830 so that the device 800 may perform any process of the disclosure as discussed with reference to FIGS. 2 to 6. The embodiments of the present disclosure may also be implemented by hardware or by a combination of software and hardware.

[0164] In some example embodiments, the program 830 may be tangibly contained in a computer readable medium which may be included in the device 800 (such as in the memory 820) or other storage devices that are accessible by the device 800. The device 800 may load the program 830 from the computer readable medium to the RAM 822 for execution. The computer readable medium may include any types of tangible non-volatile storage, such as ROM, EPROM, a flash memory, a hard disk, CD, DVD, and the like.

[0165] FIG. 9 illustrates a block diagram of an example of a computer readable medium 900 in accordance with some example embodiments of the present disclosure. The computer readable medium 900 has the program 930 stored thereon. It is noted that although the computer readable medium 900 is depicted in form of CD or DVD in FIG. 9, the computer readable medium 900 may be in any other form suitable for carry or hold the program 930.

[0166] Generally, various embodiments of the present disclosure may be implemented in hardware or special purpose circuits, software, logic or any combination thereof. Someaspects may be implemented in hardware, while other aspects may be implemented in firmware or software which may be executed by a controller, microprocessor or other computing device. While various aspects of embodiments of the present disclosure are illustrated and described as block diagrams, flowcharts, or using some other pictorial representations, it is to be understood that the block, apparatus, system, technique or method described herein may be implemented in, as non-limiting examples, hardware, software, firmware, special purpose circuits or logic, general purpose hardware or controller or other computing devices, or some combination thereof.

[0167] The present disclosure also provides at least one computer program product tangibly stored on a non-transitory computer readable storage medium. The computer program product includes computer-executable instructions, such as those included in program modules, being executed in a device on a target real or virtual processor, to carry out the method 500 or 600 as described above with reference to FIG. 5 or 6. Generally, program modules include routines, programs, libraries, objects, classes, components, data structures, or the like that perform particular tasks or implement particular abstract data types. The functionality of the program modules may be combined or split between program modules as desired in various embodiments. Machine-executable instructions for program modules may be executed within a local or distributed device. In a distributed device, program modules may be located in both local and remote storage media.

[0168] Program code for carrying out methods of the present disclosure may be written in any combination of one or more programming languages. These program codes may be provided to a processor or controller of a general purpose computer, special purpose computer, or other programmable data processing apparatus, such that the program codes, when executed by the processor or controller, cause the functions / operations specified in the flowcharts and / or block diagrams to be implemented. The program code may execute entirely on a machine, partly on the machine, as a stand-alone software package, partly on the machine and partly on a remote machine or entirely on the remote machine or server.

[0169] In the context of the present disclosure, the computer program codes or related data may be carried by any suitable carrier to enable the device, apparatus or processor to perform various processes and operations as described above. Examples of the carrier include a signal, computer readable medium, and the like.

[0170] The computer readable medium may be a computer readable signal medium or acomputer readable storage medium. A computer readable medium may include but not limited to an electronic, magnetic, optical, electromagnetic, infrared, or semiconductor system, apparatus, or device, or any suitable combination of the foregoing. More specific examples of the computer readable storage medium would include an electrical connection having one or more wires, a portable computer diskette, a hard disk, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or Flash memory), an optical fiber, a portable compact disc read-only memory (CD-ROM), an optical storage device, a magnetic storage device, or any suitable combination of the foregoing. The term “non-transitory,” as used herein, is a limitation of the medium itself (i.e., tangible, not a signal) as opposed to a limitation on data storage persistency (e.g., RAM vs. ROM).

[0171] Further, while operations are depicted in a particular order, this should not be understood as requiring that such operations be performed in the particular order shown or in sequential order, or that all illustrated operations be performed, to achieve desirable results. In certain circumstances, multitasking and parallel processing may be advantageous. Likewise, while several specific implementation details are contained in the above discussions, these should not be construed as limitations on the scope of the present disclosure, but rather as descriptions of features that may be specific to particular embodiments. Certain features that are described in the context of separate embodiments may also be implemented in combination in a single embodiment. Conversely, various features that are described in the context of a single embodiment may also be implemented in multiple embodiments separately or in any suitable sub-combination.

[0172] Although the present disclosure has been described in languages specific to structural features and / or methodological acts, it is to be understood that the present disclosure defined in the appended claims is not necessarily limited to the specific features or acts described above. Rather, the specific features and acts described above are disclosed as example forms of implementing the claims.

Claims

WHAT IS CLAIMED IS:

1. A first non-terrestrial network (NTN) device comprising: at least one processor; and at least one memory storing instructions that, when executed by the at least one processor, cause the first NTN device at least to: based on receiving a first registration request from a terminal device and not having a connectivity with a terrestrial network (TN) device, store the first registration request; and transmit, to the terminal device, an identifier assigned to the terminal device.

2. The first NTN device of claim 1, wherein the first NTN device is further caused to: transmit, to the terminal device, validity time for the identifier assigned to the terminal device.

3. The first NTN device of claim 1, wherein the first NTN device is further caused to: assign the identifier to the terminal device based on an identifier of the first NTN device.

4. The first NTN device of any of claims 1-3, wherein the first NTN device is further caused to: when having the connectivity with the TN device, transmit, to the TN device, the first registration request and the identifier assigned to the terminal device.

5. The first NTN device of any of claims 1-4, wherein the first NTN device is further caused to: transmit, to the TN device, location information of the terminal device with the first registration request and the identifier assigned to the terminal device.

6. The first NTN device of any of claims 1-5, wherein the first NTN device is further caused to:receive, from the TN device, a non-access stratum (NAS) request targeting the terminal device and the identifier assigned to the terminal device.

7. The first NTN device of claim 5, wherein the first NTN device is further caused to: connect to the terminal device by using the identifier of the terminal device; transmit, to the terminal device, the NAS request targeting the terminal device; and receive, from the terminal device, an NAS response.

8. The first NTN device of claim 7, wherein the first NTN device is further caused to: connect to the terminal device by paging the terminal device using the identifier of the terminal device.

9. The first NTN device of claim 7, wherein the first NTN device is further caused to: connect the terminal device by paging the terminal device using the identifier of the terminal device and the location of the terminal device.

10. The first NTN device of claim 7, wherein the first NTN device is further caused to: when not having connectivity with the TN device, store the NAS response; and when having the connectivity with the TN device, transmit, to the TN device, the NAS response.

11. The first NTN device of any of claims 1-10, wherein the first NTN device is a non-terrestrial access and mobility management function (AMF-NT); and the TN device is a terrestrial AMF.

12. The first NTN device of any of claims 1-10, wherein the first NTN device is a non-terrestrial Mobility Management Entity (MME); and the TN device is a terrestrial MME.

13. A terrestrial network (TN) device comprising: at least one processor; and at least one memory storing instructions that, when executed by the at least one processor, cause the TN device at least to: receive, from a first non-terrestrial network (NTN) device, an identifier assigned to a terminal device and a first registration request; and start an authentication for a terminal device using the identifier assigned to the terminal device.

14. The TN device of claim 13, wherein the TN device is further caused to start the authentication for the terminal device by: selecting a third network device based on a Subscription Permanent Identifier (SUPI or IMSI) or a Subscription Concealed Identifier (SUCI); receiving authentication data from the third network device; and storing the authentication data against the identifier assigned to the terminal device.

15. The TN device of claim 13 or 14, wherein the TN device is further caused to: receive, from the first NTN device, location information of the terminal device with the first registration request and the identifier assigned to the terminal device.

16. The TN device of any of claims 13-15, wherein the TN device is further caused to: transmit, to a second NTN device, a NAS request targeting the terminal device and the identifier assigned to the terminal device.

17. The TN device of any of claims 13-16, wherein the TN device is further caused to: transmit, to a second NTN device, a NAS request targeting the terminal device and the identifier assigned to the terminal device and location information associated with the device.

18. The TN device of claim 16, wherein the TN device is further caused to: receive a NAS response from the second NTN device.

19. The TN device of any of claims 13-18, wherein the first NTN device is a nonterrestrial access and mobility management function (AMF-NT); and the TN device is a terrestrial AMF.

20. The TN device of any of claims 13-18, wherein the first NTN device is a nonterrestrial Mobility Management Entity (MME); and the TN device is a terrestrial MME.

21. A terminal device comprising: at least one processor; and at least one memory storing instructions that, when executed by the at least one processor, cause the terminal at least to: transmit, to a first non-terrestrial network (NTN) device, a first registration request; and receive, from the first NTN device, an identifier assigned to the terminal device in response to the first registration request.

22. The terminal device of claim 21, wherein the terminal device is further caused to: receive, from the first NTN device validity time for the identifier assigned to the terminal device.

23. The terminal device of claim 21 or 22, wherein the terminal device is further caused to: connect to a second NTN device by using the identifier of the terminal device; receive, from the second NTN device, a NAS request targeting the terminal device; and transmit, to the second NTN device, an NAS response.

24. A method comprising: based on receiving a first registration request from a terminal device and not having a connectivity with a terrestrial network (TN) device, storing the first registration request; and transmitting, to the terminal device, an identifier assigned to the terminal device.

25. A method comprising: receiving, from a first NTN device, an identifier assigned to a terminal device and a first registration request; and starting an authentication for a terminal device using the identifier assigned to the terminal device.

26. A method comprising: transmitting, to a first NTN device, a first registration request; and receiving, from the first NTN device, an identifier assigned to the terminal device in response to the first registration request.

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