WO2024243880A1

WO2024243880A1 - Dynamic non-access stratum timer value in non-terrestrial network

Info

Publication number: WO2024243880A1
Application number: PCT/CN2023/097538
Authority: WO
Inventors: Xiang Xu; Mads LAURIDSEN; Ping Yuan; Sung Hwan Won; Hannu Petri Hietalahti
Original assignee: Nokia Shanghai Bell Co Ltd; Nokia Solutions and Networks Oy; Nokia Technologies Oy
Current assignee: Nokia Shanghai Bell Co Ltd; Nokia Solutions and Networks Oy; Nokia Technologies Oy
Priority date: 2023-05-31
Filing date: 2023-05-31
Publication date: 2024-12-05
Anticipated expiration: 2025-11-30

Abstract

Example embodiments of the present disclosure relate to a dynamic non-access stratum (NAS) timer value in a non-terrestrial network (NTN). A first core network device determines NAS timer information based on NTN information of at least one NTN access network device or the reception of the NAS timer information from a second core network device. The NAS timer information comprises at least one of first NAS timer information to be used by at least one terminal device or second NAS timer information to be used by the first core network device. If the NAS timer information comprises the first NAS timer information, the first core network device transmits the first NAS timer information to one of the at least one terminal device via one of the at least one NTN access network device. In this way, the reliability and efficiency of the NTN communication are improved.

Description

DYNAMIC NON-ACCESS STRATUM TIMER VALUE IN NON-TERRESTRIAL NETWORK

FIELD

Various example embodiments relate to the field of telecommunication, and in particular, to core network devices, a terminal device, an access network device, methods, apparatuses and a computer readable storage medium for configuring and utilizing a dynamic non-access stratum (NAS) timer value in a non-terrestrial network (NTN) .

BACKGROUND

With development of communication technology, more and more communication scenarios may relate to a non-terrestrial network (NTN) . A NTN refers to a network or segments of a network using at least one airborne or space-borne vehicle for transmission. Airborne vehicles such as high altitude platform station (HAPS) vehicles or space-borne vehicles such as satellites may be referred to as NTN vehicles. The core network (CN) device may communicate with the terminal device via an access network device on a NTN vehicle.

Recently, a store and forward (S&F) architecture is introduced, enabling a low-cost deployment consisting of just a few NTN vehicles and a few CN devices. A key challenge in the S&F architecture is that the access network device embarked on the NTN vehicle may not have simultaneous connection with the terminal device and the CN device. Enhancements on communications in a NTN network in the S&F architecture are still needed.

SUMMARY

In general, example embodiments of the present disclosure provide a solution for configuring and utilizing a dynamic NAS timer value in a NTN network.

In a first aspect, there is provided a first core network device. The first core network device comprises a processor and a transceiver communicatively coupled to the processor. The processor is configured to cause the first core network device to: determine non-access stratum (NAS) timer information, wherein the NAS timer information is determined based on non-terrestrial network (NTN) information of at least one NTN access network device, or the reception of the NAS timer information from a second core network device, the NAS timer information comprises at least one of first NAS timer information to be used by at least one terminal device or second NAS timer information to be used by the first core network device; and in the event that the NAS timer information comprises the first NAS timer information, transmit the first NAS timer information to one of the at least one terminal device via a NTN access network device among the at least one NTN access network device.

In a second aspect, there is provided an access network device. The access network device comprises a processor and a transceiver communicatively coupled to the processor. The processor is configured to cause the access network device to: receive, from a core network device, non-access stratum (NAS) timer information to be used by at least one terminal device; and transmit, to one of the at least one terminal device, at least a subset of the NAS timer information.

In a third aspect, there is provided a terminal device. The terminal device comprises a processor and a transceiver communicatively coupled to the processor. The processor is configured to cause the terminal device to: receive, from a non-terrestrial network (NTN) access network device, at least a subset of non-access stratum (NAS) timer information; and perform a NAS procedure based on the received NAS timer information.

In a fourth aspect, there is provided a second core network device. The second core network device comprises a processor and a transceiver communicatively coupled to the processor. The processor is configured to cause the second core network device to: determine non-access stratum (NAS) timer information, wherein the NAS timer information is determined based on non-terrestrial network (NTN) information of at least one NTN access network device; and transmit the NAS timer information to the first core network device.

In a fifth aspect, there is provided a method. The method comprises: determining, at a first core network device, non-access stratum (NAS) timer information, wherein the NAS timer information is determined based on non-terrestrial network (NTN) information of at least one NTN access network device, or the reception of the NAS timer information from a second core network device, the NAS timer information comprises at least one of first NAS timer information to be used by at least one terminal device or second NAS timer information to be used by the first core network device; and in the event that the NAS timer information comprises the first NAS timer information, transmitting the first NAS timer information to one of the at least one terminal device via a NTN access network device among the at least one NTN access network device.

In a sixth aspect, there is provided a method. The method comprises: receiving, at an access network device from a core network device, non-access stratum (NAS) timer information to be used by at least one terminal device; and transmitting, to one of the at least one terminal device, at least a subset of the NAS timer information.

In a seventh aspect, there is provided a method. The method comprises: receiving, at a terminal device from a non-terrestrial network (NTN) access network device, at least a subset of non-access stratum (NAS) timer information; and performing a NAS procedure based on the received NAS timer information.

In an eighth aspect, there is provided a method. The method comprises: determining, at a second core network device, non-access stratum (NAS) timer information, wherein the NAS timer information is determined based on non-terrestrial network (NTN) information of at least one NTN access network device; and transmitting the NAS timer information to the first core network device.

In a ninth aspect, there is provided an apparatus. The apparatus comprises: means for determining, at a first core network device, non-access stratum (NAS) timer information, wherein the NAS timer information is determined based on non-terrestrial network (NTN) information of at least one NTN access network device, or the reception of the NAS timer information from a second core network device, the NAS timer information comprises at least one of first NAS timer information to be used by at least one terminal device or second NAS timer information to be used by the first core network device; and means for in the event that the NAS timer information comprises the first NAS timer information, transmitting the first NAS timer information to one of the at least one terminal device via a NTN access network device among the at least one NTN access network device.

In a tenth aspect, there is provided an apparatus. The apparatus comprises: means for receiving, at an access network device and from a core network device, non-access stratum (NAS) timer information to be used by at least one terminal device; and means for transmitting, to one of the at least one terminal device, at least a subset of the NAS timer information.

In an eleventh aspect, there is provided an apparatus. The apparatus comprises: means for receiving, at a terminal device and from a non-terrestrial network (NTN) access network device, at least a subset of non-access stratum (NAS) timer information; and means for performing a NAS procedure based on the received NAS timer information.

In a twelfth aspect, there is provided an apparatus. The apparatus comprises: means for determining, at a second core network device, non-access stratum (NAS) timer information, wherein the NAS timer information is determined based on non-terrestrial network (NTN) information of at least one NTN access network device; and means for transmitting the NAS timer information to the first core network device.

In a thirteenth aspect, there is provided a first core network device. The first core network device comprises: determining circuitry configured to determine non-access stratum (NAS) timer information, wherein the NAS timer information is determined based on non-terrestrial network (NTN) information of at least one NTN access network device, or the reception of the NAS timer information from a second core network device, the NAS timer information comprises at least one of first NAS timer information to be used by at least one terminal device or second NAS timer information to be used by the first core network device; and transmitting circuitry configured to in the event that the NAS timer information comprises the first NAS timer information, transmit the first NAS timer information to one of the at least one terminal device via a NTN access network device among the at least one NTN access network device.

In a fourteenth aspect, there is provided an access network device. The access network device comprises: receiving circuitry configured to receive from a core network device, non-access stratum (NAS) timer information to be used by at least one terminal device; and transmitting circuitry configured to transmit, to one of the at least one terminal device, at least a subset of the NAS timer information.

In a fifteenth aspect, there is provided a terminal device. The terminal device comprises: receiving circuitry configured to receive from a non-terrestrial network (NTN) access network device, at least a subset of non-access stratum (NAS) timer information; and performing circuitry configured to perform a NAS procedure based on the received NAS timer information.

In a sixteenth aspect, there is provided a second core network device. The second core network device comprises: determining circuitry configured to determine non-access stratum (NAS) timer information, wherein the NAS timer information is determined based on non-terrestrial network (NTN) information of at least one NTN access network device; and transmitting circuitry configured to transmit the NAS timer information to the first core network device.

In a seventeenth 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 fifth to seventh aspect.

In an eighteenth 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 fifth to seventh aspect.

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

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

FIG. 1A illustrates an example of a network environment in which some example embodiments of the present disclosure may be implemented;

FIG. 1B illustrates an example S&F operation in some example embodiments of the present disclosure;

FIG. 1C illustrates an example registration procedure for initial registration related to some example embodiments of the present disclosure;

FIG. 1D illustrates another example registration procedure related to some example embodiments of the present disclosure;

FIG. 2A illustrates an example of a process flow for configuring and utilizing a dynamic NAS timer value in NTN in accordance with some example embodiments of the present disclosure;

FIG. 2B illustrates another example of a process flow for configuring and utilizing a dynamic NAS timer value in NTN in accordance with some example embodiments of the present disclosure;

FIG. 3 illustrates an example operation procedure of using a dynamic NAS timer value in accordance with some example embodiments of the present disclosure;

FIG. 4 illustrates a flowchart of a method implemented at a first core network device in accordance with some example embodiments of the present disclosure;

FIG. 5 illustrates a flowchart of a method implemented at an access network device in accordance with some other embodiments of the present disclosure;

FIG. 6 illustrates a flowchart of a method implemented at a terminal device in accordance with some other embodiments of the present disclosure;

FIG. 7 illustrates a flowchart of a method implemented at a first core network device in accordance with some example embodiments of the present disclosure;

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

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

Throughout the drawings, the same or similar reference numerals represent the same or similar elements.

DETAILED DESCRIPTION

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 only for 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.

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.

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.

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.

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: <a list of two or more elements>” and “at least one of <a list of two or more elements>” and similar wording, where the list of two or more elements are joined by “and” or “or” , mean at least any one of the elements, or at least any two or more of the elements, or at least all the elements.

As used in this application, the term “circuitry” may refer to one or more or all of the following:

(a) hardware-only circuit implementations (such as implementations in only analog and/or digital circuitry) 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/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.

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.

As used herein, the term “communication network” refers to a network following any suitable communication standards, such as Long Term Evolution (LTE) , LTE-Advanced (LTE-A) , 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 in the communication network may be performed according to any suitable generation 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 disclosure may be applied in various communication systems. 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.

As used herein, the term “network device” refers to a node in a communication network via which a terminal device accesses the network and receives services therefrom. The network device may refer to a base station (BS) or an access point (AP) , for example, a node B (NodeB or NB) , an evolved NodeB (eNodeB or eNB) , a new radio (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, and so forth, depending on the applied terminology and technology.

The term “terminal device” refers to any end device that may be capable of wireless communication. By way of example rather than limitation, a terminal device may also be referred to as a communication device, user equipment (UE) , a Subscriber Station (SS) , a Portable Subscriber Station, a Mobile Station (MS) , or an Access Terminal (AT) . The terminal device may 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, vehicle-mounted 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 commercial and/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.

Non-terrestrial networks (NTN) have been defined for NR and Narrowband Internet of Things/enhanced Machine Type Communication (NB-IoT/eMTC) . The S&F operation in a NTN is intended to provide some level of communication service (in storing and forwarding the data) under satellite coverage with intermittent/temporary satellite connectivity, e.g. to provide communication service for UEs under satellite coverage without a simultaneous active feeder link connection to the ground segment. This is particularly relevant for delay-tolerant IoT services via Non-Geosynchronous Orbit (NGSO) space segment.

The S&F operation builds on the Release 18 concept of discontinuous coverage scenario, where the UE only occasionally and temporarily has coverage from a satellite. The discontinuous coverage scenario is expanded by now also defining that the satellite is not always connected with the core network. The S&F architecture enables a low-cost deployment consisting of just a few satellites and a few ground stations. This means that the connection cost per device can be further reduced at the cost of only being able to support delay tolerant data.

The S&F architecture may mainly refer to a NGSO satellite as an example, and assumes the radio access network (RAN) node (e.g. gNB) is hosted in the satellite. A key challenge in the store and forward deployment is the satellite/gNB may not have simultaneous connection with the UE and the CN device.

For illustrative purposes only, various aspects of example embodiments will be described in the context of gNB/NR. It should be appreciated, however, that the description herein may be applicable to eNB/LTE and other radio access network nodes. For illustrative purposes only, various aspects of example embodiments will be described in the context of satellite. It should be appreciated, however, that the description herein may be applicable to other space-borne vehicles than satellites, airborne vehicles such as HAPS vehicles or other NTN vehicles with an access network device (or a radio access network device) onboard.

Due to the fact that the S&F gNB may not be able to follow the earth rotation, the NGSO satellite/gNB may not serve the geographical area of the UE in each pass around the earth. For example, the NGSO satellite/gNB may serve the geographical area of the UE in one pass, but it may not serve the geographical area of the UE in the next pass. So it is possible that different satellites/gNBs serve the geographical area of the UE at different times.

When the UE initiates a NAS procedure (e.g. Registration) , it normally starts a NAS timer (e.g., T3510) . The NAS timer stops when the UE receives a NAS response (e.g. REGISTRATION ACCEPT) . In Release 16/17 NTN, the gNB has simultaneous connection with the UE and the CN device. The NAS timer is extended to consider the long delays between the UE and the satellite, and between the satellite and the NTN-GW for Medium Earth Orbit (MEO) and Geostationary Earth Orbit (GEO) . For example, for normal terrestrial network, T3510 is 15s and 85s for WB-N1/CE mode, and 27s for access via a satellite NG-RAN cell. The NAS timer values (e.g. T3510 and T3519 on UE side and T3550 and T3570 on AMF side) are defined in TS 24.501.

However, in the S&F architecture, the gNB may first only connect with a UE for a period, then only connect with CN device via a transport network node, e.g. a NTN Gateway (NTN-GW) , for another period, and optionally neither connect with the UE or CN device for yet another period. So the duration from the time point that the UE sends a NAS message (e.g. a REGISTRATION REQUEST message) till the time point that the UE receives the response (e.g. a REGISTRATION ACCEPT message) is largely affected by many factors, such as the duration that the gNB does not have connection with the CN device, the duration that the gNB does not have connection with the UE, the number of satellites, and the number of NTN-GWs. For example, the delay is very different for a S&F system with one satellite and one NTN-GW, and another S&F system with 50 satellites and 20 NTN-GWs. The duration is also affected by the satellite type (e.g., a Low Earth Orbit (LEO) satellite or a MEO satellite) , the location of the NTN-GW, and the location of the UE relative to the satellite constellation.

The average time between satellite availabilities for different constellations and UE locations may vary dramatically. For example, the time may vary between 1 hour and 4 hours depending only on the UE location. Thus, it is not practical to use a fixed timer value as defined in TS 24.501 for the NAS timers.

In addition, it is not sufficient to just extend the NAS timers. For example, if a lower layer failure or a release of the access stratum (AS) signaling connection is detected, currently, the NAS layer would abort the procedure. Therefore, enhancements are needed to avoid procedure abortion even if a lower layer failure or a release of the AS signaling connection occurs, if the RAN node is in the S&F operation mode.

In view of the above discussions, some example embodiments of the present disclosure are provided to improve the reliability and efficiency of the NTN communication. Principles and some example embodiments of the present disclosure will be described in detail below with reference to the accompanying drawings.

FIG. 1A illustrates an example of a network environment 100 in which some example embodiments of the present disclosure may be implemented. In the descriptions of the example embodiments of the present disclosure, the network environment 100 may also be referred to as a non-terrestrial network (NTN) or a communication system 100 (for example, a portion of a communication network) . For illustrative purposes only, various aspects of example embodiments will be described in the context of one or more core network devices, access network devices, and terminal devices that communicate with one another. It should be appreciated, however, that the description herein may be applicable to other types of apparatus or other similar apparatuses that are referenced using other terminology.

The communication system 100 includes a terminal device 110, an access network device 120, a gateway or NTN gateway 130 and a CN device 140. The gateway 130 is an earth station located at the surface of the earth, providing connectivity to the NTN payload using the feeder link. The gateway 130 is a transport network layer (TNL) node. The NTN payload is a network node, embarked on board a satellite or high altitude platform station, providing connectivity functions, between the service link that is a wireless link between the NTN payload and the terminal device, and the feeder link that is a wireless link between the NTN Gateway and the NTN payload. In the S&F system, the NTN payload is the access network device 120. The access network device 120 may be connected with the terminal device 110 and/or the gateway 130 over a wireless network, such as a wireless radio access network (e.g., a 3G wireless access network, a 4G-Long Term Evolution (LTE) network, a 5G-New Radio (e.g., 5G) wireless network, a future 6G wireless network, a future 7G wireless network, etc. ) . The gateway 130 and the CN device 140 may connect to each other over a wired and/or wireless network. The access network device 120 can provide connection to the CN device 140 through at least one NTN-GW (e.g., the gateway 130) , thereby providing radio connection between the terminal device 110 and the CN device 140.

In some embodiments, the terminal device 110 may be any one of, but not limited to, a mobile device, a tablet, a laptop computer, a wearable device, an IoT device, a desktop computer and/or any other type of stationary or portable device capable of operating according to the 5G NR communication standard, and/or other wireless communication standard. In release 17 and release 18, the NTN has been defined for NR and NB-IoT/eMTC devices. The NTN may enable the communication sessions between the terminal device 110 and the CN device 140 efficiently due to attributes of IOT data traffic, such as small data transmission (SDT) with few packets, early data transmission (EDT) , preconfigured uplink resources (PUR) and/or non-critical delivery time.

In some embodiments, the access network device 120 may be a radio access network (RAN) device in a non-terrestrial network (NTN) and may thus be referred to as a NTN access network device. For example, the access network device 120 may be a gNB or eNB embarked on a NTN vehicle such as a low earth orbiting (LEO) satellite, a medium earth orbiting (MEO) satellite, a geostationary earth orbiting (GEO) satellite, a UAS device (e.g., a drone, a blimp, a balloon, etc. ) , a HAPS vehicle, or a manned aerial vehicle (MAV) device, etc. Further, there may be a plurality of NTN vehicles that act as a constellation of NTN vehicles, providing a coordinated coverage area among the plurality of NTN vehicles, e.g., a constellation of satellites, a constellation of UASs, and/or a constellation of satellites and UASs, etc.

In the following, a satellite will be used as an example of a NTN vehicle for describing some specific example embodiments of the present disclosure. It is noted that example embodiments described with regard to the satellite are equally applicable to any other suitable types of NTN vehicles. It should be understood that the satellite in the present disclosure corresponds to an access network device (for example, an eNB or gNB, or part of the eNB, or part of the gNB) . In the following, the expression “a satellite communicates with a terminal device or a CN device” should be interpreted as that an access network device onboard the satellite communicates with a terminal device or a CN device. If multiple base stations are embarked on one satellite, further (direct) identification of the access network device is required. As used herein, each satellite has at least one access network device onboard and a reference to a satellite entails a reference to the access network device onboard.

In some embodiments, the CN device 140 may implement any suitable functionality. For example, the CN device 140 may have access to data network, Internet or one or more other types of public, semiprivate or private networks. The CN device 140 may be implemented as multiple core network elements that provide different network functions. Communications between the access network device 120 and the CN device 140 through the gateway 130 in both directions may be called feeder links, whereas communications between the access network device 120 and the terminal device 110 in both directions may be called service links.

In some embodiments, the CN device 140 may be a 4G Evolved Packet Core (EPC) network. The access network device 120 may provide connection to a Mobility Management Entity (MME) or a S-GW in the EPC network. In some embodiments, the CN device 140 may be a 5G core network. The access network device 120 may provide connection to an Access and Mobility Management Function (AMF) in the 5G core network. In some example implementations, the CN device 140 may include a first core network device, e.g., an AMF device or a MME device, and a second core network device, e.g., an Application Function (AF) device.

As shown in FIG. 1A, the access network device 120 may have discontinuous connection with the CN device 140 and the terminal device 110 (as shown in dashed lines) . For example, when the access network device 120 is located at location A, the access network device 120 may have connection 111 with the terminal device 110 while having no connection 112 with the gateway 130 and thus having no connection with the CN device 140. The access network device 120 may receive data from the terminal device 110 at the location A and store the received data. As the access network device 120 moves from the location A to location B, the access network device 120 may have no connection 113 with the terminal device 110 while having connection 114 with the gateway 130 and thus having connection with the CN device 140. Alternatively, at the location B, the access network device 120 may have both of the connection 113 with the terminal device 110 and the connection 114 with the CN device 140. With connection to the CN device 140, the access network device 120, at the location B, may transmit the stored data to the CN device 140.

It is to be understood that the number of core network devices, gateways, access network devices and terminal devices is only for the purpose of illustration without suggesting any limitations. The system 100 may include any suitable number of core network devices, gateways, access network devices and terminal devices adapted for implementing embodiments of the present disclosure.

Communications in the network environment 100 may be implemented according to any proper communication protocol (s) , comprising, but not limited to, cellular communication protocols of the fourth generation (4G) and the fifth generation (5G) and on the like, wireless local network communication protocols such as Institute for Electrical and Electronics Engineers (IEEE) 802.11 and the like, and/or any other protocols currently known or to be developed in the future. Moreover, the communication may utilize any proper wireless communication technology, comprising but not limited to: Code Division Multiple Access (CDMA) , Frequency Division Multiple Access (FDMA) , Time Division Multiple Access (TDMA) , Frequency Division Duplex (FDD) , Time Division Duplex (TDD) , Multiple-Input Multiple-Output (MIMO) , Orthogonal Frequency Division Multiple (OFDM) , Discrete Fourier Transform spread OFDM (DFT-s-OFDM) and/or any other technologies currently known or to be developed in the future.

FIG. 1B illustrates an example S&F operation 150 in some example embodiments of the present disclosure. For the purpose of discussion, the S&F operation 150 will be described with reference to FIG. 1A. The example implementation of the S&F operation 150 is depicted and will be described from perspectives of a terminal device 110, a first satellite SAT1 with a first access network device gNB1 onboard, a second satellite SAT2 with a second access network device gNB2 onboard, a third satellite SAT3 with a third access network device gNB3 onboard, a first gateway 130-1, a second gateway 130-2 and a CN device 140. More particularly, the satellites SAT1, SAT2 and SAT3 move relative to the gateways. Each of the gNB1, gNB2 and gNB3 may communicate with the CN device 140 when it is connected to any of the first and second gateways 130-1 and 130-2. The connection between the CN device 140 and each of the gNB1, gNB2 and gNB3 is temporary and discontinuous. Each of the access network devices gNB1, gNB2 and gNB3 may communicate with the UE 110 when its coverage footprint overlaps the location of the UE 110. The connection between the UE 110 and each of the access network devices gNB1, gNB2 and gNB3 is temporary and discontinuous. The CN device 140 communicates with the UE 110 via the gateways 130-1 and 130-2 and the access network devices gNB1, gNB2 and gNB3.

In the S&F operation 150, at T1, gNB1 serves the geographical area of the terminal device 110 and has connection 111-1 with the terminal device 110, but it has no connection with the gateways and the CN device. The gNB1 may receive data (e.g., a NAS message) from the terminal device 110 and store the received data. At T2, gNB1 moves out the geographical area of the terminal device 110, and it has connection 114-1 with the first gateway 130-1. The gNB1 forward the stored data of the UE to the first gateway 130-1, then the first gateway 130-1 forwards the data received from the gNB1 to the CN device 140. The gNB2 serves the geographical area of the terminal device 110, but it has no connection with the gateways and the CN device. The gNB3 has connection 114-2 with the second gateway 130-2. The CN device 140 may transmit responding data to gNB3 through the second gateway 130-2. The gNB3 may store the responding data. At T3, the gNB3 serves the geographical area of the terminal device 110 and has connection 111-2 with the terminal device 110. The gNB3 may transmit the stored responding data to the terminal device 110.

Due to the fact that the satellites SAT1, SAT2 and SAT3 may be NGSO satellites and may not be able to follow the earth rotation, the gNB1, gNB2 and gNB3 may not serve the geographical area of the terminal device 110 in each pass around the earth. For example, the gNB1 may serve the geographical area of the terminal device 110 in one pass, but it may not serve the geographical area of the terminal device 110 in the next pass. So it is possible that different gNBs serve the geographical area of the terminal device 110 at different times.

FIG. 1C illustrates an example registration procedure 160 for initial registration related to some example embodiments of the present disclosure. For the purpose of discussion, the registration procedure 160 will be described with reference to FIG. 1A. The example implementation of the registration procedure 160 is depicted and will be described from perspectives of a UE 170 and an AMF 141. The UE 170 may be implemented as a terminal device, for example, the terminal device 110 in FIG. 1A. The AMF 141 may be implemented in one or more core network devices, for example, the core network device 140 in FIG. 1A.

As shown in FIG. 1C, the UE 170 may initiate a NAS procedure (e.g. a registration procedure 160) by transmitting a NAS message (e.g. a REGISTRATION REQUEST message 161) to the AMF 141. The UE 170 may start a NAS timer (i.e., T3510) when transmitting the REGISTRATION REQUEST message 161. The NAS timer T3510 stops when the UE 170 receives a NAS response (e.g. a REGISTRATION ACCEPT message 162) from the AMF 141. Alternatively, the NAS timer T3510 stops when the UE 170 receives another NAS response (e.g. a REGISTRATION REJECT message 164) from the AMF 141. It is to be understood that the communication between the UE 170 and the AMF 141 uses an access network device (e.g. gNB) that is not shown in FIG. 1C.

The AMF 141 may start a NAS timer (i.e., T3550) when transmitting the REGISTRATION ACCEPT message 162 to the UE 170. The NAS timer T3550 stops when the AMF 141 receives a NAS response (e.g. a REGISTRATION COMPLETE message 163) from the UE 170.

FIG. 1D illustrates another example registration procedure related to some example embodiments of the present disclosure. The illustrated registration procedure is defined in TS 23.502. In FIG. 1D, UE refers to User Equipment, (R) AN refers to (Radio) Access Network, AMF refers to Access and Mobility Management Function, PCF refers to Policy Control Function, SMF refers to Session Management Function, AUSF refers to Authentication Server Function, and UDM refers to Unified Data Management.

It is noted that any one or more of the old and new AMFs, the PCF, the SMF, the AUSF, and the UDM may be implemented in one or more core network devices, for example, the core network device 140 in FIG. 1A. It is to be understood that these core network functions are described only for the purpose of illustration without suggesting any limitation as to the scope of the disclosure.

A UE needs to register with the network to get authorized to receive services, to enable mobility tracking and to enable reachability. Details of the registration procedure in FIG. 1D may refer to TS 23.502. As is evident from FIG. 1D, the UE may transmit and receive additional messages, such as the Identity Request/Response and the Authentication/Security related messages (for further details, see TS 33.501) . For example, the transmission of the Identity Response message will trigger the timer T3519 to start, which is 65s in NTN and 90s for WB-N1/CE mode.

In addition to the UE-side timers, there are also network-side (AMF-side) timers including T3550 (which starts with transmission of a Registration Accept message) and T3570 (which starts with a Transmission of Identity Request message) . Table 1 shows some of the relevant NAS timers on UE side defined in TS 24.501. Table 2 shows some of the relevant NAS timers on AMF side defined in TS 24.501.

Table 1 NAS Timers of 5GS mobility management –UE side

Table 2 NAS Timers of 5GS mobility management –AMF side

FIG. 2A illustrates an example of a process flow 200A for configuring and utilizing a dynamic NAS timer value in NTN in accordance with some example embodiments of the present disclosure. For the purpose of discussion, the process flow 200A will be described with reference to FIG. 1A. The process 200A may involve the terminal device 110 and the access network device 120 as illustrated in FIG. 1A. The process 200A may further involve a first core network device 241. The first core network device 241 may correspond to the CN device 140 in FIG. 1A or part of the CN device 140. It would be appreciated that although the process flow 200A has been described referring to the network environment 100 of FIG. 1A, this process flow 200A may be likewise applied to other similar communication scenarios.

In the process flow 200A, the first core network device 241 determines (202) NAS timer information. In some embodiments, the NAS timer information may be determined by the first core network device 241 based on NTN information of at least one access network device. Alternatively, the NAS timer information may be determined based on a reception of the NAS timer information from a second core network device. In some embodiments, the NAS timer information may comprise first NAS timer information 206 to be used by at least one terminal device. In other words, the first NAS timer information 206 may be associated with NAS timers at UE side. Without loss of generality, the at least one terminal device may be served by the at least one access network device. For example, the at least one terminal device may be located in the coverage area or future footprint of the at least one access network device. Alternatively or additionally, the NAS timer information may comprise second NAS timer information to be used by the first core network device 241. In other words, the second NAS timer information may be associated with NAS timers at AMF side.

If the NAS timer information comprises the first NAS timer information to be used by at least one terminal device, the first core network device 241 transmits (204) the first NAS timer information 206 to the access network device 120 among the at least one access network device. For example, when the access network device 120 among the at least one access network device has connection with the first core network device 241, e.g. through at least one NTN-GW, the first core network device 241 may transmit the first NAS timer information 206 to the access network device 120. The access network device 120 receives (208) the first NAS timer information 206. Since the access network device 120 might have no connection with the terminal device 110, the access network device 120 may store the first NAS timer information 206.

When the access network device 120 connects with the terminal device 110, the access network device 120 transmits (212) at least a subset 214 of the first NAS timer information to the terminal device 110. In some embodiments, the first NAS timer information 206 to be used by at least one terminal device may be associated with multiple NAS timers. The at least a subset 214 of the first NAS timer information may be at least a portion of the first NAS timer information 206 and may be associated with at least a subset of the multiple NAS timers. For example, the first NAS timer information 206 may be associated with UE side timers defined in TS 24.501, e.g., T3502, T3510, T3511 and T3519. The at least a subset 214 of the first NAS timer information may be associated with T3510 for a registration procedure. In some embodiments, the remaining of the first NAS timer information 206 may be transmitted to the terminal device 110 at a later stage, e.g., via a NAS message.

The terminal device 110 receives (216) the at least a subset 214 of the first NAS timer information from the access network device 120. Based on the received NAS timer information, the terminal device 110 save the received NAS timer information, and use it later when the terminal device 110 performs (218) a NAS procedure.

As described above with reference to FIGS. 1A and 1B, the access network device 120 is a NTN access network device. In some embodiments, the NTN information may comprise a type of a NTN vehicle co-located with the NTN access network device 120 or a type of a NTN device that the NTN access network device 120 is embarked on, e.g., a LEO satellite or a MEO satellite. Alternatively or additionally, the NTN information may comprise a trajectory or ephemeris information associated with at least one NTN vehicle co-located with the at least one NTN access network device 120 or one NTN vehicle that the NTN access network device 120 is embarked on. Alternatively or additionally, the NTN information may comprise footprint information of the at least one NTN access network device. In the S&F architecture, the NTN access network device may not be able to follow the earth rotation and thus the footprint of the NTN access network device may change over time.

Alternatively or additionally, the NTN information may comprise a duration that the at least one NTN access network device serves a geographical area. In some embodiments, the first NAS timer information 206 may be associated with the geographical area. For example, the first NAS timer information 206 may be determined to be used by at least one terminal device located in a geographical area and may be determined at least based on a duration that the at least one NTN access network device serves a geographical area.

Alternatively or additionally, the NTN information may comprise a duration that the at least one NTN access network device connects with at least one gateway associated with the first core network device 241. As described above with reference to FIGS. 1A and 1B, the access network device 120 may communicate with the CN device 140 when the access network device 120 has connection with the gateway connected with the CN device 140. In some embodiments, the dynamic NAS timer values for NAS procedures related to communication between the core network device and the terminal device may be determined at least based on a duration that the at least one NTN access network device connects with at least one gateway associated with the core network device.

Alternatively or additionally, the NTN information may comprise a number of the at least one NTN access network device. Alternatively or additionally, the NTN information may comprise a number of the at least one gateway. Without loss of generality, the more NTN access network devices (or NTN vehicles with NTN access network devices embarked on) are deployed, the shorter the latency of NTN communication and therefore the shorter the associated NAS timer value may be. Similarly, the more gateways are deployed, the shorter the latency of NTN communication and therefore the shorter the associated NAS timer value may be. Alternatively or additionally, the NTN information may comprise at least one geographical location of the at least one gateway.

In some embodiments, the NAS timer information may comprise at least one timer value for at least one NAS procedure. The terminal device 110 may directly determine the NAS timer value based on the received first NAS timer information, and the geographical location that the terminal device 110 is located at. Similarly, the first core network device 241 may directly determine the NAS timer value based on the second NAS timer information. For example, the NAS timer information may include values of the UE-side NAS timers and the CN-side NAS timers. In another example, the NAS timer information may include a single value which should be added to the conventional time values (e.g., for 5GS, those defined in TS 24.501) .

Alternatively or additionally, the NAS timer information may comprise a validity timing window indicating when the timer value is valid. For example, the duration that each access network device will serve a geographical area and the duration that the access network device will connect with the CN device may vary in a day, resulting in different timer values for a NAS timer that have different validity timing window. For example, the timer value for a NAS timer may be determined to vary in a day, e.g. a first value to be used for [5: 00 –12: 00] and a second value to be used for [13: 00 –23: 00] , and thus the first and second values may be associated with different validity timing windows (e.g., [5: 00 –12: 00] and [13: 00 –23: 00] , respectively) during which the timer value is valid.

Alternatively or additionally, the NAS timer information may comprise an index of the at least one timer value. In other words, the NAS timer information may comprise an index which represents a set of values for the NAS timers. For example, multiple timer values for a NAS timer may be predefined or specified. The terminal device 110 may determine the NAS timer value based on a timer value index in the first NAS timer information. Similarly, the first core network device 241 may determine the NAS timer value based on a timer value index in the second NAS timer information. In this way, the transmission resource for the NAS timer information may be reduced. Alternatively or additionally, the NAS timer information may comprise an indication that the NTN access network device is in a storage and forward mode.

In some embodiments, at least one of the first NAS timer information 206 or the second NAS timer information may be associated with a geographical area. In other words, the first NAS timer information 206 may be different for each geographical area. Alternatively or additionally, the second NAS timer information may be different for each geographical area. For example, when transmitting the first NAS timer information 206, the first core network device 241 may transmit a list of first NAS timer information associated with a list of geographical areas. The list of first NAS timer information may comprise the first NAS timer information, and the list of geographical areas may comprise the geographical area. In other words, the first core network device 241 may transmit, to the access network device 120, a list of first NAS timer information corresponding to multiple geographical areas, respectively. In some examples, the multiple geographical areas may cover the coverage area of the access network device 120, or the future coverage of the access network device 120. Alternatively, when transmitting the first NAS timer information 206, the first core network device 241 may transmit a list of items, and each item includes the first NAS timer information and the information of the associated geographical area. In other words, the first core network device 241 may transmit, to the access network device 120, a list of items and each item corresponding to a geographical area, respectively. In some examples, the multiple geographical areas may cover the coverage area of the access network device 120, or the future coverage of the access network device 120.

In some embodiments, the geographical area may be identified by a cell identity (ID) . Alternatively or additionally, the geographical area may be identified by a tracking area code (TAC) . Alternatively or additionally, the geographical area may be identified by a list of TACs. Alternatively or additionally, the geographical area may be identified by a registration area ID. Alternatively or additionally, the geographical area may be identified by a public land mobile network (PLMN) ID. Alternatively or additionally, the geographical area may be identified by an area ID based on a network definition.

In some embodiments, the first core network device 241 may be an AMF device or a MME device, and the second core network device may be an application function (AF) device.

In some embodiments, the NAS timer information may be determined periodically. Alternatively or additionally, the determination of the NAS timer information may be event-triggered. For example, when the number of access network devices (or NTN vehicles with access network devices embarked on) serving a geographical area is changed, the determination of the NAS timer information may be triggered. Alternatively or additionally, the NAS timer information may be determined based on an operation, administration and maintenance (OAM) . For example, the NAS timer information may be determined when a new NTN-GW is deployed.

In some embodiments, the first core network device 241 may perform a NAS procedure based on the second NAS timer information. In order to perform the NAS procedure, the first core network device 241 may determine a timer value for the NAS procedure based on the second NAS timer information. Based on initiating the NAS procedure, the first core network device 241 may start a NAS timer with a duration of the timer value.

In some embodiments, in order to perform the NAS procedure, the first core network device 241 may start a NAS timer with a duration of a pre-determined timer value based on initiating the NAS procedure. After determining the NAS timer information either by itself or based on a reception from the second core network device, the first core network device 241 may determine a timer value for the NAS procedure based on the second NAS timer information and update the NAS timer value based on the determined timer value.

In some embodiments, the access network device 120 may transmit to the terminal device 110 an indication that the access network device 120 is in a storage and forward mode. Alternatively or additionally, the access network device 120 may transmit to the first core network device 241 an indication that the access network device 120 is in a storage and forward mode.

For example, the first core network device 241 may receive, from the access network device 120, an indication that the (at least one) access network device is in a storage and forward mode. In some implementations, the first core network device 241 may receive, from another access network device among the at least one access network device, an indication that the (at least one) access network device is in a storage and forward mode. Based on determining that the (at least one) access network device is in a storage and forward mode, the first core network device 241 may avoid aborting a NAS procedure in an event of a lower layer failure. Alternatively or additionally, based on determining that the (at least one) access network device is in a storage and forward mode, the first core network device 241 may avoid aborting a NAS procedure in an event of a release of an access stratum (AS) signaling connection.

In some example, implementations, if the core network device is indicated that S&F operation is used in the RAN node, the core network device may not abort the ongoing procedure even if there is a lower layer failure or a release of an AS signaling connection. In order to achieve this enhancement, the NGAP or S1AP layer in the core network device needs to forward an indication that S&F operation is used in the RAN node to the NAS layer of the core network device. Alternatively, the first core network device (e.g. an AMF device) may receive this indication from the second core network device (e.g. an AF device) .

Continuing with reference to FIG. 2A, the access network device 120 may receive the first NAS timer information and information of the geographical area associated with the first NAS timer information. In one example implementation, the access network device 120 may receive a list of first NAS timer information corresponding to multiple geographical areas that cover the coverage area or future coverage area of the access network device 120. In some implementations, the access network device 120 may transmit, to the terminal device 110, (a subset of) the first NAS timer information in the list of first NAS timer information which corresponds to a geographical area in which the terminal device 110 is located. For example, the at least a subset 214 of the first NAS timer information may be transmitted to the terminal device 110 via an unicast message.

In some implementations, the at least a subset 214 of the first NAS timer information may be transmitted to the terminal device 110 via a broadcast message. For example, the access network device 120 may broadcast a message (e.g., a system information block (SIB) ) comprising a sub-list of first NAS timer information in the list of first NAS timer information. The sub-list of first NAS timer information may correspond to at least one geographical area in the footprint of the access network device 120. In other words, the sub-list of first NAS timer information broadcast via SIB may only include a subset of the list of first NAS timer information received from the first core network device 241. In some examples, the remaining of the list of first NAS timer information may be provided to the terminal device 110 via a dedicated radio resource control (RRC) procedure. The terminal device 110 may determine the NAS timer value from the sub-list of first NAS timer information based on the geographical area in which the terminal device 110 is located.

In some embodiments, the at least a subset 214 of the first NAS timer information may be transmitted to the terminal device 110 via a RRC signaling. Alternatively or additionally, the at least a subset 214 of the first NAS timer information may be transmitted to the terminal device 110 via a NAS message. For example, a subset of the first NAS timer information may be transmitted to the terminal device 110 via a RRC signaling and the remaining of the first NAS timer information may be transmitted to the terminal device 110 via a NAS message. In other words, a hybrid RRC+NAS procedure may be used, e.g. some NAS timer information may be provided to the terminal device via RRC signaling (e.g. SIB) , and other (or updated) NAS timer information may be provided to the terminal device via NAS signaling.

In an example implementation, the terminal device 110 may receive a SIB via the access stratum (AS) layer of the terminal device 110. The AS layer of the terminal device 110 may provide the NAS layer of the terminal device 110 with the first NAS timer information in the SIB. The terminal device 110 may initiate the NAS procedure (e.g., a registration procedure) and start the NAS timer (i.e. T3510) whose value is determined using the first NAS timer information in the SIB. Before the access network device 120 stops to serve the geographical area of the terminal device 110, the access network device 120 may send a RRCRelease message which may include other first NAS timer information. Alternatively, the access network device 120 may provide the first NAS timer information via a dedicated RRC procedure before the RRCRelease procedure. In short, a CN entity/function may determine the first NAS timer information and provide it to RAN node (s) and an AMF/MME device (e.g. in case an AF device determines it) . The RAN node (after a possible processing) broadcasts (a subset of) the first NAS timer information. Based on the broadcast information, a terminal device may determine values of the NAS timers. Via the above procedures, the terminal device and the AMF/MME may use the dynamic NAS timer value accordingly.

In another example implementation, a CN entity/function may determine the first NAS timer information and provide it to a terminal device via one or more NAS messages (e.g., the REGISTRATION ACCEPT message) through RAN node (s) . The terminal device may store the first NAS timer information and use it to determine values of the UE-side NAS timers in a specific geographical area corresponding to a cell identity (ID) , or a tracking area code (TAC) , or a list of tracking area codes, or a registration area ID, or a PLMN ID, or any other area ID based on network definition or operator planning.

The first NAS timer information received by the terminal device may be applicable in the whole geographical area in which the terminal device is located. For example, the geographical area may be a PLMN which is currently selected by the terminal device or the current registration area. The first NAS timer information may be transmitted along with geographical area information. The geographical area is identified by a cell ID, a TAC, a list of tracking area identifiers, a registration area ID, a PLMN ID, or any other area ID.

In some embodiments, in order to perform the NAS procedure, the terminal device 110 may determine a timer value for the NAS procedure based on the at least a subset 214 of first NAS timer information. Based on initiating the NAS procedure, the terminal device 110 may start a NAS timer with a duration of the timer value.

In some embodiments, in order to perform the NAS procedure, the terminal device 110 may start a NAS timer with a duration of a pre-determined timer value based on initiating the NAS procedure. After receiving the at least a subset 214 of first NAS timer information, the terminal device 110 may determine a timer value for the NAS procedure based on the at least a subset 214 of first NAS timer information and update the NAStimer value based on the determined timer value.

In an example implementation, an element of the first NAS timer information may be associated with an additional timer. This additional timer may be started when the element is newly stored or modified. When the additional timer expires, the element may be deleted. The first NAS timer information may be (pre-) configured in the terminal device (e.g., in the universal subscriber identity module) . The terminal device may prioritize the first NAS timer information received via the NAS signaling over the pre-configured one. In addition, the terminal device may prioritize the first NAS timer information received via SIB over the first NAS timer information retrieved via other source.

Based on determining that the access network device 120 is in a storage and forward mode, the terminal device 110 may avoid aborting a NAS procedure in an event of a lower layer failure. Alternatively or additionally, based on determining that the access network device 120 is in a storage and forward mode, the terminal device 110 may avoid aborting a NAS procedure in an event of a release of an AS signaling connection.

In some example implementations, if the terminal device is indicated that S&F operation is used in the RAN node, the terminal device may not abort the ongoing procedure even if there is a lower layer failure or a release of an AS signaling connection. In order to achieve this enhancement, the AS layer of the terminal device needs to forward an indication that S&F operation is used in the RAN node to the NAS layer of the terminal device.

Through the process flow 200A, both the terminal device and the first core network device can send S&F type uplink (UL) and downlink (DL) signaling and data. Both the terminal device and the first core network device can use an appropriate NAS timer value dynamically determined based on the NTN information, which enables the network to optimize the NAS timer values to avoid expiry or too long delays before expiry. In this way, the reliability and efficiency of the NTN communication may be improved.

FIG. 2B illustrates another example of a process flow 200B for configuring and utilizing a dynamic NAS timer value in NTN in accordance with some example embodiments of the present disclosure. It is noted that the process flow 200B can be performed in combination with or in addition to the process flow 200A. For the purpose of discussion, the process flow 200B will be described with reference to FIG. 1A. The process 200A may involve the first core network device 241 and a second core network device 242. The first core network device 241 and the second core network device 242 may correspond to different core network elements in the CN device 140. It would be appreciated that although the process flow 200B has been described referring to the network environment 100 of FIG. 1A, this process flow 200B may be likewise applied to other similar communication scenarios.

In the process flow 200B, the second core network device 242 determines (222) NAS timer information 226. The NAS timer information 226 is determined by the second core network device 242 based on NTN information of at least one NTN access network device. The second core network device 242 transmits (224) the NAS timer information 226 to the first core network device 241. The first core network device 241 receives (228) the NAS timer information 226.

In some embodiments, the NAS timer information 226 may comprise first NAS timer information to be used by at least one terminal device. Alternatively or additionally, the NAS timer information may comprise second NAS timer information to be used by the first core network device 241.

In some embodiments, the NTN information may comprise a type of a NTN vehicle co-located with the NTN access network device 120 or a type of a NTN vehicle that the NTN access network device 120 is embarked on, e.g., a LEO satellite or a MEO satellite. Alternatively or additionally, the NTN information may comprise a trajectory or ephemeris information associated with at least one NTN vehicle that the at least one NTN access network device is embarked on. Alternatively or additionally, the NTN information may comprise footprint information of the at least one NTN access network device.

Alternatively or additionally, the NTN information may comprise a duration that the at least one NTN access network device serves a geographical area. Alternatively or additionally, the NTN information may comprise a duration that the at least one NTN access network device connects with at least one gateway associated with the first core network device 241. Alternatively or additionally, the NTN information may comprise a number of the at least one NTN access network device. Alternatively or additionally, the NTN information may comprise a number of the at least one gateway. Alternatively or additionally, the NTN information may comprise at least one geographical location of the at least one gateway.

In some embodiments, the NAS timer information may comprise at least one timer value for at least one NAS procedure. Alternatively or additionally, the NAS timer information may comprise a validity timing window indicating when the timer value is valid. Alternatively or additionally, the NAS timer information may comprise an index of the at least one timer value. Alternatively or additionally, the NAS timer information may comprise an indication that the at least one NTN access network device is in a storage and forward mode.

In some embodiments, the NAS timer information may be associated with a geographical area. For example, the NAS timer information may be associated with a geographical area, e.g. in which the at least one terminal device is located. In particular, the first NAS timer information may be associated with a geographical area, e.g. in which the at least one terminal device is located.

In some embodiments, the geographical area may be identified by a cell ID. Alternatively or additionally, the geographical area may be identified by a TAC or a list of TACs. Alternatively or additionally, the geographical area may be identified by a registration area ID. Alternatively or additionally, the geographical area may be identified by a PLMN ID. Alternatively or additionally, the geographical area may be identified by an area ID based on a network definition.

In some embodiments, the first core network device 241 may be an AMF device or a MME device, and the second core network device 242 may be an AF device. For example, the AMF/MME device may receive the NAS timer information from the AF device via the network exposure function/service capability exposure function (NEF/SCEF) . In some embodiments, the NAS timer information may be determined periodically. Alternatively or additionally, the determination of the NAS timer information may be event-triggered. Alternatively or additionally, the NAS timer information may be determined based on an OAM.

Through the process flow 200B, appropriate NAS timer values may be dynamically determined based on the NTN information, which enables the network to optimize the NAS timer values to avoid expiry or too long delays before expiry. In this way, the reliability and efficiency of the NTN communication may be improved.

FIG. 3 illustrates an example operation procedure 200A of using a dynamic NAS timer value in accordance with some example embodiments of the present disclosure. It is noted that the operation procedure 200A can be deemed as a more specific example of the process flow 200. The example implementation of FIG. 3 is depicted and will be described from perspectives of a UE1 310, a gNB1 320 and a CN node 340. More particularly, the gNB1 320 may be an access network device onboard a satellite SAT1. It should be understood that the UE1 310, the gNB1 320 and the CN node 340 may correspond to the terminal device 110, the access network device 120 and the CN device 140 in FIG. 1A, respectively. The CN node 340 may communicate with the gNB1 320 through at least one NTN-GW (e.g., the gateway 130 in FIG. 1A) .

It is to be understood that the operation procedure 200A may involve any suitable number of CN devices and access network devices adapted for implementing embodiments of the present disclosure. In other words, the operations of the gNB1 320 may be implemented by any suitable number of access network devices, and the operations of the CN node 340 may be implemented by any suitable number of CN devices. For example, although the operation procedure 200A uses one satellite/gNB as an example, it is similar when multiple satellites/gNBs are involved. In some examples, a satellite has one gNB onboard, and in the following, a reference to a satellite entails a reference to the onboard gNB, and vice versa. It is to be understood that operation procedure 200A may further include additional blocks not shown and/or omit some shown blocks, and the scope of the present disclosure is not limited in this regard.

At T0, the gNB1 320 may have connection with the CN node 340. At 302, the CN node 340 may transmit at least one determined value for at least one UE-side NAS timer to the gNB1 320 through at least one NTN-GW. In one example, an AMF device in the CN node 340 may determine values for at least one UE-side NAS timer and at least one AMF-side NAS timer, considering the satellite information, such as satellite type (e.g., LEO stallite or MEO satellite) , ephemeris information, satellite footprint (i.e., a changing footprint area on earth over time) , the estimated duration that each satellite will serve a geographical area, the estimated duration that the satellite will connect with the CN node, the number of satellites, the number of gateways, the location of the gateways, etc.

In some embodiments, each geographical area may have its own set of NAS timer values. In other words, the CN node 340 may determine multiple sets of NAS timer values for at least one UE-side NAS timer and at least one AMF-side NAS timer. Each set of NAS timer values may correspond to a respective geographical area. For example, a specific geographical area may be served by more satellites while another geographical area may be served by fewer satellites. So the information provided to the gNB1 320 can be a list of items, where each item corresponds to at least one UE-side NAS timer value for a respective geographical area. The geographical area can be identified by at least one of a cell identity (ID) , a tracking area code (TAC) , a list of TACs, a registration area ID, a PLMN ID, or an otherwise area identity (as per network indication/definition) .

In some embodiments, the NAS timer value may vary every day or even in a day, e.g. one value to be used for [5: 00 –12: 00] and another value to be used for [13: 00 –23: 00] . For example, the duration that each satellite will serve a geographical area and the duration that the satellite will connect with the CN node may vary in a day, resulting in different timer values for a NAS timer corresponding to a geographical area. Each timer value may be associated with a validity timing window (e.g., [5: 00 –12: 00] or [13: 00 –23: 00] ) during which the timer value is valid.

In another example, the NAS timer value determination may be performed by an application function (AF) device in the CN node 340 in a similar manner as the NAS timer value determination by the AMF device. The AMF device may receive the multiple sets of NAS timer values for at least one UE-side NAS timer and at least one AMF-side NAS timer from the AF device via NEF/SCEF.

The AMF device may store the determined NAS timer value (s) for at least one AMF-side NAS timer for further NAS operations. In this way, the AMF device may use the corresponding NAS timer value, either determined by the AMF device itself if the NAS timer value is determined by the AMF device, or received from an AF device if the NAS timer value is determined by the AF device.

The NAS timer value determination may be performed periodically, or event-triggered (e.g. when the number of satellites serving a geographical area is changed) , or based on OAM (e.g. when a new NTN-GW is deployed) .

At 304, the gNB1 320 may move in the geographical area of the UE1 310, and can serve the UE1 310. At 306, the gNB1 320 may broadcast the NAS timer value via SIB. The UE1 310 may receive the SIB, and store the NAS timer value for further NAS operations. Since a satellite beam (Uu cell) may cover a very large area including multiple geographical areas, the SIB may include multiple sets of NAS timer value, e.g. one set of NAS timer value for each geographical area. The UE1 310 may determine the set of NAS timer values from the multiple sets of NAS timer value based on the geographical area it is located. In one example, the SIB may include the value for all UE-side NAS timers. In other words, the UE1 310 may obtain all NAS timer values needed for further NAS operations.

In another example, due to limited message size of SIB, the SIB may only include some NAS timer values. For example, the SIB may only include the value for the NAS timer (s) that need to be started when UE sends UL NAS message via the RRCSetupComplete message. For example, T3510 is for the case that the UE’s UL NAS REGISTRATION REQUEST is sent via the RRCSetupComplete message, and T3517 is for the case when the UE sends UL NAS SERVICE REQUEST via the RRCSetupComplete message. In some examples, the SIB may only include the values for T3510 and T3517. Values for the other UE-sider NAS timers may be transmitted in a subsequent RRC signaling or NAS message.

At 308, the UE1 310 may transmit a RRCSetupRequest message to the gNB1 320. At 312, the gNB1 320 may transmit a RRCSetup message to the UE1 310. At 314, the UE1 310 may transmit a RRCSetupComplete message to the gNB1 320. The RRCSetupComplete message may include the NAS REGISTRATION REQUEST message. The UE may start a NAS timer T3510 with a timer value received in step 306. In this way, a dynamic NAS timer value is used for the NAS operation in NTN S&F architecture.

At 316, since the UE1 310 does not have any other message to send, the gNB1 320 may initiate a RRCRelease message including the timer values for other UE-side NAS timers. This could be the NAS timer other than the NAS timer values already included in SIB (in step 306) . The UE1 310 may save these NAS timer values and use them in the later NAS procedures.

In some other examples, the dynamic NAS timer information for the NAS timer T3510 may be provided to the UE1 310 via the RRCRelease message rather than via SIB. For example, the UE1 310 may use a pre-configured value for T3510 when it starts the registration procedure at step 314. At step 316, the gNB1 320 may initiate a RRCRelease message including NAS timer information for T3510. The UE1 310 may determine the timer value for the timer T3510 based on the received NAS timer information and update the timer T3510 to the determined timer value.

At 318, the gNB1 320 may move out of the geographical area of the UE1 310. At 322, the gNB1 320 may have connection with the CN node 340. At 324, the gNB1 320 may transmit an initial UE message including NAS REGISTRATION REQUEST to the CN node 340. At 326, the CN node 340 may transmit a DL NAS TRANSPORT message including NAS REGISTRATION ACCEPT to the gNB1 320. When the gNB1 320 moves in the geographical area of the UE1 310 again, the gNB1 320 may transmit a NAS REGISTRATION ACCEPT message to the UE1 310 via RRC signaling. Upon receiving the NAS REGISTRATION ACCEPT message, the UE1 310 may stop the NAS timer 3510.

In some examples, the dynamic NAS timer information may be provided to the UE1 310 via a NAS procedure. For example, the REGISTRATION ACCEPT message may include the NAS timer information determined by the CN node 340. The determined NAS timer information may be per UE’s PLMN, or per registration area, or per Tracking Area. The UE1 310 may use the received NAS timer information accordingly.

Both RRC-based approach and NAS-based approach may be used together for transmitting dynamic NAS timer information. For example, the RRC procedure (e.g. SIB or RRCRelease) may provide some NAS timer information (e.g. for T3510) , and the NAS procedure (e.g. REGISTRATION ACCEPT message) may provide other NAS timer information. The NAS procedure may also be used to provide updated NAS timer information, e.g., when a new NTN-GW is deployed before the UE1 310 performs a periodic Registration Update procedure.

In some example implementations, the steps 326 and 328 may be performed by another gNB (e.g., gNB2) in another satellite (e.g., SAT2) different from the SAT1. It should be understood, for the purpose of simplicity, the operation procedure 200A may not include all NGAP/RRC procedures used in a registration procedure.

FIG. 4 illustrates a flowchart of a method 400 implemented at a first core network device in accordance with some example embodiments of the present disclosure. For the purpose of discussion, the method 400 will be described from the perspective of the first core network device 241 with reference to FIG. 2A.

At block 410, the first core network device 241 determines non-access stratum (NAS) timer information. The NAS timer information is determined based on non-terrestrial network (NTN) information of at least one NTN access network device, or the reception of the NAS timer information from a second core network device. The NAS timer information comprises at least one of first NAS timer information to be used by at least one terminal device or second NAS timer information to be used by the first core network device 241.

At block 420, it is determined whether the NAS timer information comprises the first NAS timer information. If yes, the method 400 proceeds to block 430. At block 430, the first core network device 241 transmits the first NAS timer information to one of the at least one terminal device via a NTN access network device among the at least one NTN access network device.

In some embodiments, the NTN information may comprise a type of a NTN vehicle that the NTN access network device is embarked on. Alternatively or additionally, the NTN information may comprise a trajectory or ephemeris information associated with at least one NTN vehicle that the at least one NTN access network device is embarked on. Alternatively or additionally, the NTN information may comprise footprint information of the at least one NTN access network device. Alternatively or additionally, the NTN information may comprise a duration that the at least one NTN access network device serves a geographical area. Alternatively or additionally, the NTN information may comprise a duration that the at least one NTN access network device connects with at least one gateway associated with the first core network device 241. Alternatively or additionally, the NTN information may comprise a number of the at least one NTN access network device. Alternatively or additionally, the NTN information may comprise a number of the at least one gateway. Alternatively or additionally, the NTN information may comprise at least one geographical location of the at least one gateway.

In some embodiments, the NAS timer information may comprise at least one timer value for at least one NAS procedure. Alternatively or additionally, the NAS timer information may comprise a validity timing window indicating when the timer value is valid. Alternatively or additionally, the NAS timer information may comprise an index of the at least one timer value. Alternatively or additionally, the NAS timer information may comprise an indication that the NTN access network device is in a storage and forward mode.

In some embodiments, at least one of the first NAS timer information or the second NAS timer information may be associated with a geographical area. In some embodiments, when transmitting the first NAS timer information, the first core network device 241 may transmit the first NAS timer information and information of the geographical area associated with the first NAS timer information.

In some embodiments, the first core network device 241 may be an access and mobility management function (AMF) device or a mobility management entity (MME) device, and the second core network device may be an application function (AF) device. In some embodiments, the NAS timer information may be determined periodically, or event-triggered, or based on an operation, administration and maintenance (OAM) .

In some embodiments, the first core network device 241 may perform a NAS procedure based on the second NAS timer information. In some embodiments, when performing the NAS procedure, the first core network device 241 may determine a timer value for the NAS procedure based on the second NAS timer information; and based on initiating the NAS procedure, start a NAS timer with a duration of the timer value.

In some embodiments, when performing the NAS procedure, the first core network device 241 may start a NAS timer with a duration of a pre-determined timer value based on initiating the NAS procedure; determine a timer value for the NAS procedure based on the second NAS timer information; and update the NAS timer value based on the determined timer value.

In some embodiments, the first core network device 241 may receive, from the NTN access network device, an indication that the NTN access network device is in a storage and forward mode. In some embodiments, based on determining that the NTN access network device is in a storage and forward mode, the first core network device 241 may avoid aborting a NAS procedure in an event of a lower layer failure. Alternatively or additionally, based on determining that the NTN access network device is in a storage and forward mode, the first core network device 241 may avoid aborting a NAS procedure in an event of a release of an AS signaling connection.

Through the method 400, appropriate NAS timer values may be dynamically determined based on the NTN information, which enables the network to optimize the NAS timer values to avoid expiry or too long delays before expiry. In this way, the reliability and efficiency of the NTN communication may be improved.

FIG. 5 illustrates a flowchart of a method 500 implemented at an access network device 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 access network device 120 with reference to FIGS. 1A and 2A.

At block 510, the access network device 120 receives, from a core network device, non-access stratum (NAS) timer information to be used by at least one terminal device. At block 520, the access network device 120 transmits, to one of the at least one terminal device, at least a subset of the NAS timer information.

In some embodiments, the NAS timer information may comprise at least one timer value for at least one NAS procedure. Alternatively or additionally, the NAS timer information may comprise a validity timing window indicating when the timer value is valid. Alternatively or additionally, the NAS timer information may comprise an index of the at least one timer value. Alternatively or additionally, the NAS timer information may comprise an indication that the NTN access network device 120 is in a storage and forward mode.

In some embodiments, the NAS timer information may be associated with a geographical area. In some embodiments, the geographical area may be identified by a cell identity (ID) . Alternatively or additionally, the geographical area may be identified by a tracking area code (TAC) . Alternatively or additionally, the geographical area may be identified by a list of TACs. Alternatively or additionally, the geographical area may be identified by a registration area ID. Alternatively or additionally, the geographical area may be identified by a public land mobile network (PLMN) ID. Alternatively or additionally, the geographical area may be identified by an area ID based on a network definition.

In some embodiments, the at least a subset of the NAS timer information may be transmitted via a broadcast message. Alternatively or additionally, the at least a subset of the NAS timer information may be transmitted via an unicast message. Alternatively or additionally, the at least a subset of the NAS timer information may be transmitted via a radio resource control (RRC) signaling. Alternatively or additionally, the at least a subset of the NAS timer information may be transmitted via a NAS message.

In some embodiments, the access network device 120 may transmit, to at least one of the terminal device or the core network device, an indication that the access network device 120 is in a storage and forward mode.

Through the method 500, NAS timer information may be provided to the terminal device, which enables e the NAS timer values to be dynamically optimized to avoid expiry or too long delays before expiry. In this way, the reliability and efficiency of the NTN communication may be improved.

FIG. 6 illustrates a flowchart of a method 600 implemented at a terminal device 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 terminal device 110 with reference to FIGS. 1A and 2A.

At block 610, the terminal device 110 receives, from a non-terrestrial network (NTN) access network device, at least a subset of non-access stratum (NAS) timer information. At block 620, the terminal device 110 performs a NAS procedure based on the received NAS timer information.

In some embodiments, the NAS timer information may be associated with a geographical area in which the terminal device 110 is located. In some embodiments, the geographical area may be identified by a cell identity (ID) . Alternatively or additionally, the geographical area may be identified by a tracking area code (TAC) . Alternatively or additionally, the geographical area may be identified by a list of TACs. Alternatively or additionally, the geographical area may be identified by a registration area ID. Alternatively or additionally, the geographical area may be identified by a public land mobile network (PLMN) ID. Alternatively or additionally, the geographical area may be identified by an area ID based on a network definition.

In some embodiments, the NAS timer information may comprise a timer value for the NAS procedure. Alternatively or additionally, the NAS timer information may comprise a validity timing window indicating when the timer value is valid. Alternatively or additionally, the NAS timer information may comprise an index of the timer value. Alternatively or additionally, the NAS timer information may comprise an indication that the NTN access network device is in a storage and forward mode.

In some embodiments, when performing the NAS procedure, the terminal device 110 may determine a timer value for the NAS procedure based on the at least a subset of NAS timer information; and based on initiating the NAS procedure, start a NAS timer with a duration of the timer value.

In some embodiments, when performing the NAS procedure, the terminal device 110 may start a NAS timer with a duration of a pre-determined timer value based on initiating the NAS procedure; determine a timer value for the NAS procedure based on the at least a subset of NAS timer information; and update the NAS timer value based on the determined timer value.

In some embodiments, the at least a subset of the NAS timer information may be received via a broadcast message. Alternatively or additionally, the at least a subset of the NAS timer information may be received via an unicast message. Alternatively or additionally, the at least a subset of the NAS timer information may be received via a radio resource control (RRC) signaling. Alternatively or additionally, the at least a subset of the NAS timer information may be received via a NAS message.

In some embodiments, the terminal device 110 may receive, from the NTN access network device, an indication that the NTN access network device is in a storage and forward mode.

In some embodiments, based on determining that the NTN access network device is in a storage and forward mode, the terminal device 110 may avoid aborting a NAS procedure in an event of a lower layer failure. Alternatively or additionally, based on determining that the NTN access network device is in a storage and forward mode, the terminal device 110 may avoid aborting a NAS procedure in an event of a release of an AS signaling connection.

Through the method 600, the terminal device may obtain NAS timer information, which enables the NAS timer values to be dynamically optimized to avoid expiry or too long delays before expiry. In this way, the reliability and efficiency of the NTN communication may be improved.

FIG. 7 illustrates a flowchart of a method 700 implemented at a second core network device 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 second core network device 242 with reference to FIG. 2A.

At block 710, the second core network device 242 determines non-access stratum (NAS) timer information. The NAS timer information is determined based on non-terrestrial network (NTN) information of at least one NTN access network device. At block 720, the second core network device 242 transmits the NAS timer information to the first core network device.

In some embodiments, the NAS timer information may comprise first NAS timer information to be used by at least one terminal device. Alternatively or additionally, the NAS timer information may comprise second NAS timer information to be used by the first core network device.

In some embodiments, the NTN information may comprise a type of at least one NTN vehicle co-located with the at least one NTN access network device a type of at least one NTN vehicle that the at least one NTN access network device is embarked on. Alternatively or additionally, the NTN information may comprise a trajectory or ephemeris information associated with the at least one NTN vehicle that the at least one NTN access network device is embarked on. Alternatively or additionally, the NTN information may comprise footprint information of the at least one NTN access network device. Alternatively or additionally, the NTN information may comprise a duration that the at least one NTN access network device serves a geographical area. Alternatively or additionally, the NTN information may comprise a duration that the at least one NTN access network device connects with at least one gateway associated with the first core network device. Alternatively or additionally, the NTN information may comprise a number of the at least one NTN access network device. Alternatively or additionally, the NTN information may comprise a number of the at least one gateway. Alternatively or additionally, the NTN information may comprise at least one geographical location of the at least one gateway.

Through the method 700, appropriate NAS timer values may be dynamically determined based on the NTN information, which enables the network to optimize the NAS timer values to avoid expiry or too long delays before expiry. In this way, the reliability and efficiency of the NTN communication may be improved.

In some example embodiments, an apparatus capable of performing the method 400 (for example, the first core network device 241) may comprise means for performing the respective steps of the method 400. The means may be implemented in any suitable form. For example, the means may be implemented in a circuitry or software module.

In some example embodiments, the apparatus comprises: means for determining, at a first core network device, non-access stratum (NAS) timer information, wherein the NAS timer information is determined based on non-terrestrial network (NTN) information of at least one NTN access network device, or the reception of the NAS timer information from a second core network device, the NAS timer information comprises at least one of first NAS timer information to be used by at least one terminal device or second NAS timer information to be used by the first core network device; and means for in the event that the NAS timer information comprises the first NAS timer information, transmitting the first NAS timer information to one of the at least one terminal device via a NTN access network device among the at least one NTN access network device.

In some embodiments, the NTN information may comprise a type of a NTN vehicle co-located with the NTN access network device or a type of a NTN vehicle that the NTN access network device is embarked on. Alternatively or additionally, the NTN information may comprise a trajectory or ephemeris information associated with at least one NTN vehicle co-located with the at least one NTN access network device or a trajectory or ephemeris information associated with at least one NTN vehicle that the at least one NTN access network device is embarked on. Alternatively or additionally, the NTN information may comprise footprint information of the at least one NTN access network device. Alternatively or additionally, the NTN information may comprise a duration that the at least one NTN access network device serves a geographical area. Alternatively or additionally, the NTN information may comprise a duration that the at least one NTN access network device connects with at least one gateway associated with the first core network device. Alternatively or additionally, the NTN information may comprise a number of the at least one NTN access network device. Alternatively or additionally, the NTN information may comprise a number of the at least one gateway. Alternatively or additionally, the NTN information may comprise at least one geographical location of the at least one gateway.

In some embodiments, at least one of the first NAS timer information or the second NAS timer information may be associated with a geographical area. In some embodiments, means for transmitting the first NAS timer information may comprise means for transmitting the first NAS timer information and information of the geographical area associated with the first NAS timer information.

In some embodiments, the first core network device may be an access and mobility management function (AMF) device or a mobility management entity (MME) device, and the second core network device may be an application function (AF) device. In some embodiments, the NAS timer information may be determined periodically, or event-triggered, or based on an operation, administration and maintenance (OAM) .

In some embodiments, the apparatus may comprise means for performing a NAS procedure based on the second NAS timer information. In some embodiments, means for performing the NAS procedure may comprise means for determining a timer value for the NAS procedure based on the second NAS timer information; and means for based on initiating the NAS procedure, starting a NAS timer with a duration of the timer value.

In some embodiments, means for performing the NAS procedure may comprise means for starting a NAS timer with a duration of a pre-determined timer value based on initiating the NAS procedure; means for determining a timer value for the NAS procedure based on the second NAS timer information; and means for updating the NAS timer value based on the determined timer value.

In some embodiments, the apparatus may comprise means for receiving, from the NTN access network device, an indication that the NTN access network device is in a storage and forward mode. In some embodiments, the apparatus may comprise means for avoiding aborting a NAS procedure in an event of a lower layer failure based on determining that the NTN access network device is in a storage and forward mode. Alternatively or additionally, the apparatus may comprise means for avoiding aborting a NAS procedure in an event of a release of an AS signaling connection based on determining that the NTN access network device is in a storage and forward mode.

In some example embodiments, the apparatus further comprises means for performing other steps in some example embodiments of the method 400. In some example 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 are configured to, with the at least one processor, cause the performance of the apparatus.

In some example embodiments, an apparatus capable of performing the method 500 (for example, the access network device 120) may comprise means for performing the respective steps 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.

In some example embodiments, the apparatus comprises: means for receiving, at an access network device and from a core network device, non-access stratum (NAS) timer information to be used by at least one terminal device; and means for transmitting, to one of the at least one terminal device, at least a subset of the NAS timer information.

In some embodiments, the apparatus may comprise means for transmitting, to at least one of the terminal device or the core network device, an indication that the access network device is in a storage and forward mode.

In some example embodiments, the apparatus further comprises means for performing other steps in some example embodiments of the method 500. In some example 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 are configured to, with the at least one processor, cause the performance of the apparatus.

In some example embodiments, an apparatus capable of performing the method 600 (for example, the terminal device 110) may comprise means for performing the respective steps 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.

In some example embodiments, the apparatus comprises: means for receiving, at a terminal device and from a non-terrestrial network (NTN) access network device, at least a subset of non-access stratum (NAS) timer information; and means for performing a NAS procedure based on the received NAS timer information.

In some embodiments, means for performing the NAS procedure may comprise means for determining a timer value for the NAS procedure based on the at least a subset of NAS timer information; and means for based on initiating the NAS procedure, starting a NAS timer with a duration of the timer value.

In some embodiments, means for performing the NAS procedure may comprise means for starting a NAS timer with a duration of a pre-determined timer value based on initiating the NAS procedure; means for determining a timer value for the NAS procedure based on the at least a subset of NAS timer information; and means for updating the NAS timer value based on the determined timer value.

In some embodiments, the apparatus may comprise means for receiving, from the NTN access network device, an indication that the NTN access network device is in a storage and forward mode. In some embodiments, the apparatus may comprise means for avoiding aborting a NAS procedure in an event of a lower layer failure based on determining that the NTN access network device is in a storage and forward mode. Alternatively or additionally, the apparatus may comprise means for avoiding aborting a NAS procedure in an event of a release of a an AS signaling connection based on determining that the NTN access network device is in a storage and forward mode.

In some example embodiments, the apparatus further comprises means for performing other steps in some example embodiments of the method 600. In some example 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 are configured to, with the at least one processor, cause the performance of the apparatus.

In some example embodiments, an apparatus capable of performing the method 700 (for example, the second core network device 242) may comprise means for performing the respective steps of the method 700. The means may be implemented in any suitable form. For example, the means may be implemented in a circuitry or software module.

In some example embodiments, the apparatus comprises: means for determining non-access stratum (NAS) timer information, wherein the NAS timer information is determined based on non-terrestrial network (NTN) information of at least one NTN access network device; and means for transmitting the NAS timer information to the first core network device.

In some embodiments, the NTN information may comprise a type of at least one NTN vehicle co-located with the at least one NTN access network device or a type of at least one NTN vehicle that the at least one NTN access network device is embarked on. Alternatively or additionally, the NTN information may comprise a trajectory or ephemeris information associated with the at least one NTN vehicle or a trajectory or ephemeris information associated with at least one NTN vehicle that the at least one NTN access network device is embarked on. Alternatively or additionally, the NTN information may comprise footprint information of the at least one NTN access network device. Alternatively or additionally, the NTN information may comprise a duration that the at least one NTN access network device serves a geographical area. Alternatively or additionally, the NTN information may comprise a duration that the at least one NTN access network device connects with at least one gateway associated with the first core network device. Alternatively or additionally, the NTN information may comprise a number of the at least one NTN access network device. Alternatively or additionally, the NTN information may comprise a number of the at least one gateway. Alternatively or additionally, the NTN information may comprise at least one geographical location of the at least one gateway.

In some example embodiments, the apparatus further comprises means for performing other steps in some example embodiments of the method 700. In some example 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 are configured to, with the at least one processor, cause the performance of the apparatus.

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 110, the access network devices 120, the CN device 140, the first core network device 241 or the second core network device 242 as shown in FIG. 1A, 2A or 2B. 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.

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.

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 have multiple processors, such as an application specific integrated circuit chip that is slaved in time to a clock which synchronizes the main processor.

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.

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.

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. 2A to 7. The embodiments of the present disclosure may also be implemented by hardware or by a combination of software and hardware.

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.

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 1030 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 830.

Generally, various embodiments of the present disclosure may be implemented in hardware or special purpose circuits, software, logic or any combination thereof. Some aspects 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.

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 400, 500, 600 or 700 as described above with reference to FIG. 4, 5, 6 or 7. 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.

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.

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.

The computer readable medium may be a computer readable signal medium or a computer 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) .

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.

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

A first core network device comprising:

a processor; and

a transceiver communicatively coupled to the processor,

the processor configured to cause the first core network device to:

determine non-access stratum (NAS) timer information, wherein the NAS timer information is determined based on non-terrestrial network (NTN) information of at least one NTN access network device, or the reception of the NAS timer information from a second core network device, the NAS timer information comprises at least one of first NAS timer information to be used by at least one terminal device or second NAS timer information to be used by the first core network device; and

in the event that the NAS timer information comprises the first NAS timer information, transmit the first NAS timer information to one of the at least one terminal device via a NTN access network device among the at least one NTN access network device.
The first core network device of claim 1, wherein the NTN information comprises at least one of the following:

a type of a NTN vehicle that the NTN access network device is embarked on;

a trajectory or ephemeris information associated with at least one NTN vehicle that the at least one NTN access network device is embarked on;

footprint information of the at least one NTN access network device;

a duration that the at least one NTN access network device serves a geographical area;

a duration that the at least one NTN access network device connects with at least one gateway associated with the first core network device;

a number of the at least one NTN access network device;

a number of the at least one gateway; or

at least one geographical location of the at least one gateway.
The first core network device of claim 1 or 2, wherein the NAS timer information comprises at least one of the following:

at least one timer value for at least one NAS procedure;

a validity timing window indicating when the timer value is valid;

an index of the at least one timer value; or

an indication that the NTN access network device is in a storage and forward mode.
The first core network device of any of claims 1-3, wherein at least one of the first NAS timer information or the second NAS timer information is associated with a geographical area.
The first core network device of claim 4, wherein the first core network device is caused to transmit the first NAS timer information by:

transmitting the first NAS timer information and information of the geographical area associated with the first NAS timer information.
The first core network device of any of claims 2, 4 or 5, wherein the geographical area is identified by at least one of the following:

a cell identity (ID) ;

a tracking area code (TAC) ;

a list of TACs;

a registration area ID;

a public land mobile network (PLMN) ID; or

an area ID based on a network definition.
The first core network device of any of claims 1-6, wherein the first core network device is an access and mobility management function (AMF) device or a mobility management entity (MME) device, and the second core network device is an application function (AF) device.
The first core network device of any of claims 1-7, wherein the NAS timer information is determined periodically, or event-triggered, or based on an operation, administration and maintenance (OAM) .
The first core network device of any of claims 1-8, wherein the first core network device is further caused to:

perform a NAS procedure based on the second NAS timer information.
The first core network device of claim 9, wherein the first core network device is caused to perform the NAS procedure by:

determining a timer value for the NAS procedure based on the second NAS timer information; and

based on initiating the NAS procedure, starting a NAS timer with a duration of the timer value.
The first core network device of claim 9, wherein the first core network device is caused to perform the NAS procedure by:

based on initiating the NAS procedure, starting a NAS timer with a duration of a pre-determined timer value;

determining a timer value for the NAS procedure based on the second NAS timer information; and

updating the NAS timer value based on the determined timer value.
The first core network device of any of claims 1-11, wherein the first core network device is further caused to:

receive, from the NTN access network device, an indication that the NTN access network device is in a storage and forward mode.
The first core network device of any of claims 1-12, wherein the first core network device is further caused to:

based on determining that the NTN access network device is in a storage and forward mode, avoid aborting a NAS procedure in an event of at least one of (i) a lower layer failure or (ii) a release of an access stratum (AS) signaling connection.
An access network device comprising:

a processor; and

a transceiver communicatively coupled to the processor,

the processor configured to cause the access network device to:

receive, from a core network device, non-access stratum (NAS) timer information to be used by at least one terminal device; and

transmit, to one of the at least one terminal device, at least a subset of the NAS timer information.
The access network device of claim 14, wherein the NAS timer information comprises at least one of the following:

at least one timer value for at least one NAS procedure;

a validity timing window indicating when the timer value is valid;

an index of the at least one timer value; or

an indication that the access network device is in a storage and forward mode.
The access network device of claim 14 or 15, wherein the NAS timer information is associated with a geographical area.
The access network device of claim 16, wherein the geographical area is identified by at least one of the following:

a cell identity (ID) ;

a tracking area code (TAC) ;

a list of TACs;

a registration area ID;

a public land mobile network (PLMN) ID; or

an area ID based on a network definition.
The access network device of any of claims 14-17, wherein the at least a subset of the NAS timer information is transmitted via at least one of the following:

a broadcast message;

an unicast message;

a radio resource control (RRC) signaling; or

a NAS message.
The access network device of any of claims 14-18, wherein the access network device is further caused to:

transmit, to at least one of the at least one terminal device or the core network device, an indication that the access network device is in a storage and forward mode.
A terminal device comprising:

a processor; and

a transceiver communicatively coupled to the processor,

the processor configured to cause the terminal device to:

receive, from a non-terrestrial network (NTN) access network device, at least a subset of non-access stratum (NAS) timer information; and

perform a NAS procedure based on the received NAS timer information.
The terminal device of claim 20, wherein the NAS timer information is associated with a geographical area in which the terminal device is located.
The terminal device of claim 21, wherein the geographical area is identified by at least one of the following:

a cell identity (ID) ;

a tracking area code (TAC) ;

a list of TACs;

a registration area ID;

a public land mobile network (PLMN) ID; or

an area ID based on a network definition.
The terminal device of any of claims 20-22, wherein the at least a subset of NAS timer information comprises at least one of the following:

a timer value for the NAS procedure;

a validity timing window indicating when the timer value is valid; or

an index of the timer value; or

an indication that the NTN access network device is in a storage and forward mode.
The terminal device of any of claims 20-23, wherein the terminal device is caused to perform the NAS procedure by:

determining a timer value for the NAS procedure based on the at least a subset of NAS timer information; and

based on initiating the NAS procedure, starting a NAS timer with a duration of the timer value.
The terminal device of claim 23, wherein the terminal device is caused to perform the NAS procedure by:

based on initiating the NAS procedure, starting a NAS timer with a duration of a pre-determined timer value;

determining a timer value for the NAS procedure based on the at least a subset of NAS timer information; and

updating the NAS timer value based on the determined timer value.
The terminal device of any of claims 20-25, wherein the at least a subset of NAS timer information is received via at least one of the following:

a broadcast message;

an unicast message;

a radio resource control (RRC) signaling; or

a NAS message.
The terminal device of any of claims 20-26, wherein the terminal device is further caused to:

receive, from the NTN access network device, an indication that the NTN access network device is in a storage and forward mode.
The terminal device of any of claims 20-27, wherein the terminal device is further caused to:

based on determining that the NTN access network device is in a storage and forward mode, avoid aborting a NAS procedure in an event of at least one of (i) a lower layer failure or (ii) a release of an access stratum (AS) signaling connection.
A second core network device comprising:

a processor; and

a transceiver communicatively coupled to the processor,

the processor configured to cause the second core network device to:

determine non-access stratum (NAS) timer information, wherein the NAS timer information is determined based on non-terrestrial network (NTN) information of at least one NTN access network device; and

transmit the NAS timer information to the first core network device.
The second core network device of claim 29, wherein the NAS timer information comprises at least one of the following:

first NAS timer information to be used by at least one terminal device; or

second NAS timer information to be used by the first core network device.
The second core network device of claim 29 or 30, wherein the NTN information comprises at least one of the following:

a type of at least one NTN vehicle that the at least one NTN access network device is embarked on;

a trajectory or ephemeris information associated with the at least one NTN vehicle that the at least one NTN access network device is embarked on;

footprint information of the at least one NTN access network device;

a duration that the at least one NTN access network device serves a geographical area;

a duration that the at least one NTN access network device connects with at least one gateway associated with the first core network device;

a number of the at least one NTN access network device;

a number of the at least one gateway; or

at least one geographical location of the at least one gateway.
The second core network device of any of claims 29-31, wherein the NAS timer information comprises at least one of the following:

at least one timer value for at least one NAS procedure;

a validity timing window indicating when the timer value is valid;

an index of the at least one timer value; or

an indication that the at least one NTN access network device is in a storage and forward mode.
The second core network device of any of claims 29-31, wherein the NAS timer information is associated with a geographical area.
The second core network device of claim 31 or 33, wherein the geographical area is identified by at least one of the following:

a cell identity (ID) ;

a tracking area code (TAC) ;

a list of TACs;

a registration area ID;

a public land mobile network (PLMN) ID; or

an area ID based on a network definition.
The second core network device of any of claims 29-34, wherein the first core network device is an access and mobility management function (AMF) device or a mobility management entity (MME) device, and the second core network device is an application function (AF) device.
The second core network device of any of claims 29-35, wherein the NAS timer information is determined periodically, or event-triggered, or based on an operation, administration and maintenance (OAM) .
A method comprising:

determining, at a first core network device, non-access stratum (NAS) timer information, wherein the NAS timer information is determined based on non-terrestrial network (NTN) information of at least one NTN access network device, or the reception of the NAS timer information from a second core network device, the NAS timer information comprises at least one of first NAS timer information to be used by at least one terminal device or second NAS timer information to be used by the first core network device; and

in the event that the NAS timer information comprises the first NAS timer information, transmitting the first NAS timer information to one of the at least one terminal device via a NTN access network device among the at least one NTN access network device.
A method comprising:

receiving, at an access network device and from a core network device, non-access stratum (NAS) timer information to be used by at least one terminal device; and

transmitting, to one of the at least one terminal device, at least a subset of the NAS timer information.
A method comprising:

receiving, at a terminal device and from a non-terrestrial network (NTN) access network device, at least a subset of non-access stratum (NAS) timer information; and

performing a NAS procedure based on the received NAS timer information.
A method comprising:

determining, at a second core network device, non-access stratum (NAS) timer information, wherein the NAS timer information is determined based on non-terrestrial network (NTN) information of at least one NTN access network device; and

transmitting the NAS timer information to the first core network device.
An apparatus comprising:

means for determining, at a first core network device, non-access stratum (NAS) timer information, wherein the NAS timer information is determined based on non-terrestrial network (NTN) information of at least one NTN access network device, or the reception of the NAS timer information from a second core network device, the NAS timer information comprises at least one of first NAS timer information to be used by at least one terminal device or second NAS timer information to be used by the first core network device; and

means for in the event that the NAS timer information comprises the first NAS timer information, transmitting the first NAS timer information to one of the at least one terminal device via a NTN access network device among the at least one NTN access network device.
An apparatus comprising:

means for receiving, at an access network device and from a core network device, non-access stratum (NAS) timer information to be used by at least one terminal device; and

means for transmitting, to one of the at least one terminal device, at least a subset of the NAS timer information.
An apparatus comprising:

means for receiving, at a terminal device and from a non-terrestrial network (NTN) access network device, at least a subset of non-access stratum (NAS) timer information; and

means for performing a NAS procedure based on the received NAS timer information.
An apparatus comprising:

means for determining, at a second core network device, non-access stratum (NAS) timer information, wherein the NAS timer information is determined based on non-terrestrial network (NTN) information of at least one NTN access network device; and

means for transmitting the NAS timer information to the first core network device.
A non-transitory computer readable medium comprising program instructions for causing an apparatus to perform at least the method of any of claims 37 to 40.