Method and apparatus for managing UE context in wireless communication system

Abstract

The disclosure relates to a 5G or 6G communication system for supporting a higher data transmission rate. A method performed by a first mobility management entity (MME) which is an onboard MME of a satellite in a wireless communication system is provided. The method comprises receiving, from a user equipment (UE), an attach request message associated with a non stratum access (NAS) procedure; and transmitting, to the UE, an attach accept message for the attach request message, the attach accept message including a wait timer for a subsequent NAS procedure, wherein the subsequent NAS procedure is performed based on an expiration of the wait timer.

Description

METHOD AND APPARATUS FOR MANAGING UE CONTEXT IN WIRELESS COMMUNICATION SYSTEM

[0001] The present disclosure generally relates to a wireless communication technology, and more particularly to method and system for managing user equipment (UE) context in a Store and Forward (S&F) mode in a satellite network communication system.

[0002] 5G mobile communication technologies define broad frequency bands such that high transmission rates and new services are possible, and can be implemented not only in “Sub 6GHz” bands such as 3.5GHz, but also in “Above 6GHz” bands referred to as mmWave including 28GHz and 39GHz. In addition, it has been considered to implement 6G mobile communication technologies (referred to as Beyond 5G systems) in terahertz bands (for example, 95GHz to 3THz bands) in order to accomplish transmission rates fifty times faster than 5G mobile communication technologies and ultra-low latencies one-tenth of 5G mobile communication technologies.

[0003] At the beginning of the development of 5G mobile communication technologies, in order to support services and to satisfy performance requirements in connection with enhanced Mobile BroadBand (eMBB), Ultra Reliable Low Latency Communications (URLLC), and massive Machine-Type Communications (mMTC), there has been ongoing standardization regarding beamforming and massive MIMO for mitigating radio-wave path loss and increasing radio-wave transmission distances in mmWave, supporting numerologies (for example, operating multiple subcarrier spacings) for efficiently utilizing mmWave resources and dynamic operation of slot formats, initial access technologies for supporting multi-beam transmission and broadbands, definition and operation of BWP (BandWidth Part), new channel coding methods such as a LDPC (Low Density Parity Check) code for large amount of data transmission and a polar code for highly reliable transmission of control information, L2 pre-processing, and network slicing for providing a dedicated network specialized to a specific service.

[0004] Currently, there are ongoing discussions regarding improvement and performance enhancement of initial 5G mobile communication technologies in view of services to be supported by 5G mobile communication technologies, and there has been physical layer standardization regarding technologies such as V2X (Vehicle-to-everything) for aiding driving determination by autonomous vehicles based on information regarding positions and states of vehicles transmitted by the vehicles and for enhancing user convenience, NR-U (New Radio Unlicensed) aimed at system operations conforming to various regulation-related requirements in unlicensed bands, NR UE Power Saving, Non-Terrestrial Network (NTN) which is UE-satellite direct communication for providing coverage in an area in which communication with terrestrial networks is unavailable, and positioning.

[0005] Moreover, there has been ongoing standardization in air interface architecture / protocol regarding technologies such as Industrial Internet of Things (IIoT) for supporting new services through interworking and convergence with other industries, IAB (Integrated Access and Backhaul) for providing a node for network service area expansion by supporting a wireless backhaul link and an access link in an integrated manner, mobility enhancement including conditional handover and DAPS (Dual Active Protocol Stack) handover, and two-step random access for simplifying random access procedures (2-step RACH for NR). There also has been ongoing standardization in system architecture / service regarding a 5G baseline architecture (for example, service based architecture or service based interface) for combining Network Functions Virtualization (NFV) and Software-Defined Networking (SDN) technologies, and Mobile Edge Computing (MEC) for receiving services based on UE positions.

[0006] As 5G mobile communication systems are commercialized, connected devices that have been exponentially increasing will be connected to communication networks, and it is accordingly expected that enhanced functions and performances of 5G mobile communication systems and integrated operations of connected devices will be necessary. To this end, new research is scheduled in connection with eXtended Reality (XR) for efficiently supporting AR (Augmented Reality), VR (Virtual Reality), MR (Mixed Reality) and the like, 5G performance improvement and complexity reduction by utilizing Artificial Intelligence (AI) and Machine Learning (ML), AI service support, metaverse service support, and drone communication.

[0007] Furthermore, such development of 5G mobile communication systems will serve as a basis for developing not only new waveforms for providing coverage in terahertz bands of 6G mobile communication technologies, multi-antenna transmission technologies such as Full Dimensional MIMO (FD-MIMO), array antennas and large-scale antennas, metamaterial-based lenses and antennas for improving coverage of terahertz band signals, high-dimensional space multiplexing technology using OAM (Orbital Angular Momentum), and RIS (Reconfigurable Intelligent Surface), but also full-duplex technology for increasing frequency efficiency of 6G mobile communication technologies and improving system networks, AI-based communication technology for implementing system optimization by utilizing satellites and AI (Artificial Intelligence) from the design stage and internalizing end-to-end AI support functions, and next-generation distributed computing technology for implementing services at levels of complexity exceeding the limit of UE operation capability by utilizing ultra-high-performance communication and computing resources.

[0008] A method performed by a first mobility management entity (MME) which is an onboard MME of a satellite in a wireless communication system is provided. The method comprises receiving, from a user equipment (UE), an attach request message associated with a non stratum access (NAS) procedure; and transmitting, to the UE, an attach accept message for the attach request message, the attach accept message including a wait timer for a subsequent NAS procedure, wherein the subsequent NAS procedure is performed based on an expiration of the wait timer.

[0009] A method performed by a user equipment (UE) in a wireless communication system is provided. The method comprises transmitting, to a first mobility management entity (MME) which is an onboard MME of a satellite, an attach request message associated with a non stratum access (NAS) procedure and receiving, from the first MME, an attach accept message for the attach request message, the attach accept message including a wait timer for a subsequent NAS procedure, wherein the subsequent NAS procedure is performed based on an expiration of the wait timer.

[0010] A first mobility management entity (MME) which is an onboard MME of a satellite in a wireless communication system is provided. The first MME comprises a transceiver and a controller coupled with the transceiver and configured to receive, from a user equipment (UE), an attach request message associated with a non stratum access (NAS) procedure, and transmit, to the UE, an attach accept message for the attach request message, the attach accept message including a wait timer for a subsequent NAS procedure, wherein the subsequent NAS procedure is performed based on an expiration of the wait timer.

[0011] A user equipment (UE) in a wireless communication system is provided. The UE comprises a transceiver and a controller coupled with the transceiver and configured to transmit, to a first mobility management entity (MME) which is an onboard MME of a satellite, an attach request message associated with a non stratum access (NAS) procedure, and receive, from the first MME, an attach accept message for the attach request message, the attach accept message including a wait timer for a subsequent NAS procedure, wherein the subsequent NAS procedure is performed based on an expiration of the wait timer.

[0012] These and other features, aspects, and advantages of the present embodiments are illustrated in the accompanying drawings, throughout which like reference letters indicate corresponding parts in the various figures. The embodiments herein will be better understood from the following description with reference to the drawings, in which:

[0013] FIG. 1 illustrates signaling / data traffic exchange between the UE and the network apparatus under normal / default service according to an embodiment.

[0014] FIG. 2 illustrates the end-to-end signaling / data traffic exchange between the UE and the network apparatus through the satellite network in S&F operation mode according to an embodiment.

[0015] FIG. 3 is a block diagram that illustrates the hardware components associated with the satellite network communication system according to an embodiment.

[0016] FIG. 4A is a block diagram that illustrates the hardware components associated with the UE according to an embodiment.

[0017] FIG. 4B is a block diagram that illustrates the hardware components associated with the satellite according to an embodiment.

[0018] FIG. 4C is a block diagram that illustrates the hardware components associated with the network apparatus according to an embodiment.

[0019] FIG. 5 is a sequence diagram that illustrates the UE context management in S&F mode in satellite operation according to an embodiment.

[0020] FIG. 6 is a sequence diagram that illustrates the UE context management in S&F mode in satellite operation according to an embodiment.

[0021] FIG. 7 is a sequence diagram that illustrates an example scenario of the UE context management in S&F mode in satellite operation according to an embodiment.

[0022] FIG. 8 is a sequence diagram that illustrates the UE context management in S&F mode in satellite operation according to an embodiment.

[0023] FIG. 9 is a sequence diagram that illustrates the UE context management initiated by the network apparatus in S&F mode in satellite operation according to an embodiment.

[0024] FIG. 10 is a sequence diagram that illustrates the scenario of handling the UE context in multi-satellite operation according to an embodiment.

[0025] FIG. 11 is a sequence diagram that illustrates the scenario of handling the UE context in multi-satellite operation according to an embodiment.

[0026] FIG. 12 is a flow diagram that illustrates the method for managing the UE context in the S&F mode in the satellite network communication system according to an embodiment.

[0027] FIG. 13 is a flow diagram that illustrates the method for managing the UE context in the S&F mode in the satellite network communication system according to an embodiment.

[0028] FIG. 14 illustrates a structure of a UE according to an embodiment of the disclosure.

[0029] FIG. 15 illustrates a structure of a network entity according to an embodiment of the present disclosure.

[0030] The embodiments herein and the various features and advantageous details thereof are explained more fully with reference to the non-limiting embodiments that are illustrated in the accompanying drawings and details in the following description. Descriptions of well-known components and processing techniques are omitted so as to not unnecessarily obscure the embodiments herein. Also, the various embodiments described herein are not necessarily mutually exclusive, as some embodiments can be combined with one or more other embodiments to form new embodiments. The term "or" as used herein, refers to a non-exclusive or, unless otherwise indicated. The examples used herein are intended merely to facilitate an understanding of ways in which the embodiments herein can be practiced and to further enable those skilled in the art to practice the embodiments herein. Accordingly, the examples are not be construed as limiting the scope of the embodiments herein.

[0031] As is traditional in the field, embodiments are described and illustrated in terms of blocks that carry out a described function or functions.　These blocks, which referred to herein as managers, units, modules, hardware components or the like, are physically implemented by analog and / or digital circuits such as logic gates, integrated circuits, microprocessors, microcontrollers, memory circuits, passive electronic components, active electronic components, optical components, hardwired circuits and the like, and optionally be driven by firmware and software. The circuits, for example, be embodied in one or more semiconductor chips, or on substrate supports such as printed circuit boards and the like.　The circuits constituting a block be implemented by dedicated hardware, or by a processor (e.g., one or more programmed microprocessors and associated circuitry), or by a combination of dedicated hardware to perform some functions of the block and a processor to perform other functions of the block. Each block of the embodiments be physically separated into two or more interacting and discrete blocks without departing from the scope of the proposed method.　Likewise, the blocks of the embodiments be physically combined into more complex blocks without departing from the scope of the proposed method.

[0032] The accompanying drawings are used to help easily understand various technical features and it is understood that the embodiments presented herein are not limited by the accompanying drawings. As such, the proposed method is construed to extend to any alterations, equivalents and substitutes in addition to those which are particularly set out in the accompanying drawings. Although the terms first, second, etc. used herein to describe various elements, these elements are not be limited by these terms. These terms are generally used to distinguish one element from another.

[0033] The evolution of mobile communication systems has led to the development of Fifth Generation (5G) networks, which promise to deliver higher data rates, ultra-reliable low-latency communication, and massive machine-type communication. One of the significant advancements in 5G technology is its ability to integrate Non-Terrestrial Networks (NTNs), such as satellite networks, with traditional Terrestrial Networks (TNs). This integration aims to provide ubiquitous coverage, especially in remote and underserved areas where terrestrial infrastructure is limited or non-existent.

[0034] However, ensuring seamless service continuity between New Radio (NR) terrestrial access networks and NR satellite access networks presents several challenges. These challenges are compounded when the NR terrestrial and satellite networks are owned by different operators or operate in different frequency bands (e.g., FR1 vs. FR2). Even when the networks operate in the same frequency band, maintaining service continuity without interruption remains a complex task.

[0035] One of the primary issues arises from the need for continuous connectivity between the User Equipment (UE) and the network. In scenarios where a 5G system onboard a satellite is serving the UE, the service link (link between the satellite and the UE) and the feeder link (link between the satellite and the terrestrial gateway) must be simultaneously available to ensure effective communication. However, there are instances where the feeder link connectivity is not available, leading to delays in the attach procedure. The eNodeB (eNB) and Mobility Management Entity (MME) onboard the satellite need to wait for the availability of both links before proceeding with the next steps, resulting in prolonged attach times.

[0036] This delay in the attach procedure can significantly impact the user experience, especially in time-sensitive applications that require low-latency communication. Furthermore, the existing procedures may not be optimized to handle the absence of simultaneous service and feeder link availability, leading to inefficiencies and potential service interruptions.

[0037] Another challenge is the interoperability between different Radio Access Technologies (RATs) with satellite access. While the methods and solutions for NR satellite access can be extended to other RATs such as 4G LTE, Narrowband Internet of Things (NB-IoT), and Wideband IoT (WB-IoT), the corresponding core network entities need to be adapted accordingly. For instance, the Access and Mobility Management Function (AMF) in 5G Core (5GC) needs to be replaced by the Mobility Management Entity (MME) in LTE, and the gNodeB needs to be replaced by the eNodeB.

[0038] Thus, it is desired to address the above-mentioned disadvantages, issues or other shortcomings or at least provide a useful alternative.

[0039] The principal object of the embodiments herein is to provide a system and method for managing UE context in the S&F mode in the satellite network communication system.

[0040] Another object of the embodiment herein is to indicate to the satellites and the network apparatus a change in the UE context to perform the NAS procedure efficiently.

[0041] Yet another object of the invention is to provide MME-onboards on a satellite that transmits a timer to the UE, during which the UE will not interact with any satellites.

[0042] Yet another object of the invention is to provide a UE that starts interacting with a network by performing the NAS procedure after the expiry of the timer.

[0043] Yet another object of the invention is to synchronize the UE context at the MME-ground and MME-onboards on all satellites during the duration of the timer. It is expected that within this timer duration, all MMEs on all satellites will have the latest UE context.

[0044] In an aspect, the objects are achieved by providing a method for managing the UE context in the S&F mode in the satellite network communication system. The satellite stores the first UE context associated with the UE at the satellite, where the satellite provides communication to the UE within the satellite network communication system. The satellite receives the NAS request message from the UE and creates a second UE context in response to receiving the NAS request message. Further the satellite generates the NAS accept message by adding the UE context activation timer which includes a time period for synchronizing the second UE context across the satellite network communication system. The satellite sends the NAS accept message to the UE.

[0045] In another aspect, the objects are achieved by providing the method for managing the UE context, where the UE stores the first UE context associated with a first satellite and sends a NAS request message to a first satellite to initiate the NAS procedure with a second satellite. The initiation of the NAS procedure changes the UE context from the first UE context to a second UE context. The UE receives the NAS accept message from the first satellite. The NAS accept message includes the UE context activation timer after which the UE can perform the NAS procedure with the first or the second satellite. Further the UE initiates the UE context activation timer upon receiving the NAS accept message and the UE determines whether the UE context activation timer is expired. The UE performs the NAS procedure using the second UE context upon expiration of the UE context activation timer.

[0046] In another aspect, a satellite network communication system is provided for managing UE context in the S&F mode. The satellite network communication system includes a satellite and a network apparatus where the satellite includes a processor, a memory and a UE context management controller. The UE context management controller is coupled with the memory and processor. The UE context management controller store the first UE context associated with the first satellite. The UE context management controller send the NAS request message to the first satellite to initiate the NAS procedure with the second satellite. The initiation of the NAS procedure changes the UE context from the first UE context to the second UE context. The UE context management controller receive the NAS accept message from the first satellite, where the NAS accept message includes the UE context activation timer after which the UE can perform the NAS procedure with the second satellite. Further the UE context management controller initiate the UE context activation timer upon receiving the NAS accept message and determine whether the UE context activation timer is expired. Further the UE context management controller perform the NAS procedure using the second UE context upon expiration of the UE context activation timer.

[0047] In another aspect, the objects are achieved by providing a UE for storing the first UE context associated with the first satellite. The UE sends the NAS request message to a first satellite, where the initiation of the NAS procedure changes the UE context from the first UE context to the second UE context. The UE further receives the NAS accept message from the first satellite. The NAS accept message comprises the UE context activation timer after which the UE can perform the NAS procedure with the first and the second satellite. Further the UE initiate the UE context activation timer upon receiving the NAS accept message with the UE context activation timer. The UE determine whether the UE context activation timer is expired and perform the NAS procedure using the second UE context upon expiration of the UE context activation timer.

[0048] These and other aspects of the embodiments herein will be better appreciated and understood when considered in conjunction with the following description and the accompanying drawings. It is understood, however, that the following descriptions, while indicating preferred embodiments and numerous specific details thereof, are given by way of illustration and not of limitation. Many changes and modifications be made within the scope of the embodiments herein without departing from the spirit thereof, and the embodiments herein include all such modifications.

[0049] The present invention includes an example list of NAS messages, which can include but are not limited to the following: REGISTRATION REQUEST message, DEREGISTRATION REQUEST message, SERVICE REQUEST message, CONTROL PLANE SERVICE REQUEST, IDENTITY REQUEST, AUTHENTICATION REQUEST, AUTHENTICATION RESULT, AUTHENTICATION REJECT, REGISTRATION REJECT, DEREGISTRATION ACCEPT, SERVICE REJECT, SERVICE ACCEPT, UE CONFIGURATION UPDATE command, and UE PARAMETERS UPDATE command. This list is not exhaustive and may include other similar messages.

[0050] In an embodiment, the term EMM sublayer states include, but are not limited to, the following:

[0051] 1) EMM-NULL

[0052] 2) EMM-DEREGISTERED

[0053] a) EMM-DEREGISTERED.NORMAL-SERVICE

[0054] b) EMM-DEREGISTERED.LIMITED-SERVICE

[0055] c) EMM-DEREGISTERED.ATTEMPTING-TO-ATTACH

[0056] d) EMM-DEREGISTERED.PLMN-SEARCH

[0057] e) EMM-DEREGISTERED.NO-IMSI

[0058] f) EMM-DEREGISTERED.ATTACH-NEEDED

[0059] g) EMM-DEREGISTERED.NO-CELL-AVAILABLE

[0060] h) EMM-DEREGISTERED.eCALL-INACTIVE

[0061] 3) EMM-REGISTERED-INITIATED

[0062] 4) EMM-REGISTERED

[0063] a) EMM-REGISTERED.NORMAL-SERVICE

[0064] b) EMM-REGISTERED.ATTEMPTING-TO-UPDATE

[0065] c) EMM-REGISTERED.LIMITED-SERVICE

[0066] d) EMM-REGISTERED.PLMN-SEARCH

[0067] e) EMM-REGISTERED.UPDATE-NEEDED

[0068] f) EMM-REGISTERED.NO-CELL-AVAILABLE

[0069] g) EMM-REGISTERED.ATTEMPTING-TO-UPDATE-MM

[0070] h) EMM-REGISTERED.IMSI-DETACH-INITIATED

[0071] 5) EMM-DEREGISTERED-INITIATED

[0072] 6) EMM-TRACKING-AREA-UPDATING-INITIATED

[0073] 7) EMM-SERVICE-REQUEST-INITIATED

[0074] The term5GMM sublayer statein this embodiment is at least one of the below:

[0075] 1) 5GMM-NULL

[0076] 2) 5GMM-DEREGISTERED

[0077] a) 5GMM-DEREGISTERED.NORMAL-SERVICE

[0078] b) 5GMM-DEREGISTERED.LIMITED-SERVICE

[0079] c)5GMM-DEREGISTERED.ATTEMPTING-REGISTRATION

[0080] d) 5GMM-DEREGISTERED.PLMN-SEARCH

[0081] e) 5GMM-DEREGISTERED.NO-SUPI

[0082] f) 5GMM-DEREGISTERED.NO-CELL-AVAILABLE

[0083] g) 5GMM-DEREGISTERED.eCALL-INACTIVE

[0084] h) 5GMM-DEREGISTERED.INITIAL-REGISTRATION-NEEDED

[0085] 3) 5GMM-REGISTERED-INITIATED

[0086] 4) 5GMM-REGISTERED

[0087] a) 5GMM-REGISTERED.NORMAL-SERVICE

[0088] b) 5GMM-REGISTERED.NON-ALLOWED-SERVICE

[0089] c)5GMM-REGISTERED.ATTEMPTING-REGISTRATION-UPDATE

[0090] d) 5GMM-REGISTERED.LIMITED-SERVICE

[0091] e) 5GMM-REGISTERED.PLMN-SEARCH

[0092] f) 5GMM-REGISTERED.NO-CELL-AVAILABLE

[0093] g) 5GMM-REGISTERED.UPDATE-NEEDED

[0094] 5) 5GMM-DEREGISTERED-INITIATED

[0095] 6) 5GMM-SERVICE-REQUEST

[0096] Visited Public Land Mobile Network (VPLMN):This is a Public Land Mobile Network(PLMN) different from the Home Public Land Mobile Network (HPLMN) (if the EHPLMN list is not present or is empty) or different from an EHPLMN (if the EHPLMN list is present).

[0097] Allowable PLMN:In the case of an MS operating in MS operation mode A or B, this is a PLMN which is not in the list of "forbidden PLMNs" in the MS. In the case of an MS operating in MS operation mode C or an MS not supporting A / Gb mode and not supporting Iu mode, this is a PLMN which is not in the list of "forbidden PLMNs" and not in the list of "forbidden PLMNs for GPRS service" in the MS.

[0098] Available PLMN:PLMN(s) in the given area which is / are broadcasting capability to provide wireless communication services to the UE.

[0099] Camped on a cell:The MS (ME if there is no SIM) has completed the cell selection / reselection process and has chosen a cell from which it plans to receive all available services. Note that the services may be limited, and that the PLMN or the SNPN may not be aware of the existence of the MS (ME) within the chosen cell.

[0100] EHPLMN:Any of the PLMN entries contained in the Equivalent HPLMN list.

[0101] Equivalent HPLMN list:To allow provision for multiple HPLMN codes, PLMN codes that are present within this list shall replace the HPLMN code derived from the IMSI for PLMN selection purposes. This list is stored on the USIM and is known as the EHPLMN list. The EHPLMN list may also contain the HPLMN code derived from the IMSI. If the HPLMN code derived from the IMSI is not present in the EHPLMN list then it shall be treated as a Visited PLMN for PLMN selection purposes.

[0102] Home PLMN:This is a PLMN where the MCC and MNC of the PLMN identity match the MCC and MNC of the IMSI.

[0103] Registered PLMN (RPLMN):This is the PLMN on which certain LR (location registration which is also called as registration procedure) outcomes have occurred. In a shared network the RPLMN is the PLMN defined by the PLMN identity of the CN operator that has accepted the LR.

[0104] Registration:This is the process of camping on a cell of the PLMN or the SNPN and doing any necessary LRs.

[0105] UPLMN:PLMN / access technology combination in the "User Controlled PLMN Selector with Access Technology" data file in the SIM (in priority order).

[0106] OPLMN:PLMN / access technology combination in the "Operator Controlled PLMN Selector with Access Technology" data file in the SIM (in priority order) or stored in the ME (in priority order).

[0107] The term RAT as defined in this embodiment can be one of but not limited to, NG-RAN, 5G, 4G, 3G, 2G, EPS, 5GS, NR, NR in unlicensed bands, NR Low Earth Orbit (LEO) satellite access, NR Medium Earth Orbit (MEO) satellite access, NR Geostationary Equatorial Orbit (GEO) satellite access, NR (OTHERSAT) satellite access, NR RedCap, E-UTRA, E-UTRA in unlicensed bands, NB-IoT, WB-IoT, LTE-M and others.

[0108] The 5GS registration types include initial registration, mobility registration updating, periodic registration updating, emergency registration, SNPN onboarding registration, disaster roaming initial registration, and disaster roaming mobility registration updating.

[0109] In an embodiment, the registration type is not set to disaster roaming initial registration or disaster roaming mobility registration updating. The 5GS registration type is set to a value other than "disaster roaming initial registration" or "disaster roaming mobility registration updating." At least one of the following registration types is set: initial registration, mobility registration updating, periodic registration updating, emergency registration, or SNPN onboarding registration.

[0110] PLMN selection as per 23.122 without RPLMN: The MS selects and attempts registration on any PLMN / access technology combinations if available and allowable in the following order:

[0111] either the HPLMN (if the EHPLMN list is not present or is empty) or the highest priority EHPLMN that is available (if the EHPLMN list is present),

[0112] each PLMN / access technology combination in the "User Controlled PLMN Selector with Access Technology" data file in the SIM (in priority order),

[0113] each PLMN / access technology combination in the "Operator Controlled PLMN Selector with Access Technology" data file in the SIM (in priority order) or stored in the ME (in priority order),

[0114] other PLMN / access technology combinations with received high-quality signal in random order,

[0115] other PLMN / access technology combinations in order of decreasing signal quality.

[0116] PLMN selection as per 23.122 with RPLMN:The MS selects and attempts registration on any PLMN / access technology combinations if available and allowable in the following order:

[0117] either the RPLMN or the last registered PLMN,

[0118] either the HPLMN (in case that the EHPLMN list is not present or is empty) or the highest priority EHPLMN that is available (if the EHPLMN list is present),

[0119] each PLMN / access technology combination in the "User Controlled PLMN Selector with Access Technology" data file in the SIM (in priority order),

[0120] each PLMN / access technology combination in the "Operator Controlled PLMN Selector with Access Technology" data file in the SIM (in priority order) or stored in the ME (in priority order),

[0121] other PLMN / access technology combinations with received high-quality signal in random order,

[0122] other PLMN / access technology combinations in order of decreasing signal quality.

[0123] The network used in this embodiment is explained using any 5G Core Network Function, for example, AMF. However, the network could be any 5G / EUTRAN Core Network Entities like AMF / SMF / MME / UPF, or the network could be any 5G / EUTRAN RAN Entity like eNodeB (eNB) or gNodeB (gNB) or NG-RAN, etc. The messages used or indicated in this embodiment are shown as an example. The messages could be any signaling messages between UE and the Network Functions / Entities or between different Network functions / entities. The terms area / location / geographical area used in this embodiment may refer to any of cell / cell ID, Tracking Area Code (TAC) / Tracking Area Identifier (TAI), PLMN, Mobile Country Code (MCC) / Mobile Network Code (MNC), latitude / longitude, CAG cell, or any geographical location / coordinate. The terms satellite or satellite network in this embodiment refer to the NF (e.g., AMF, SMF, UPF) onboard the satellite or 4G core network elements (e.g., MME, Serving Gateway, Packet Data Network gateway (PGW) onboard the satellite.

[0124] The methods, issues, or solutions disclosed in this embodiment are explained using New Radio (NR) access or NG-RAN Access Technology as an example and are not restricted or limited to NR access only. However, the solutions proposed in this embodiment are also applicable for E-UTRAN access Technology, NB (Narrow Band)-S1 mode, or Wide Band(WB)-S1 mode via E-UTRAN access and / or Narrowband Internet of Things (NB-IOT) or Wideband Internet of Things (WB-IOT) Access / Architecture. The solutions which are defined for NR (5GC) are also applicable to legacy RATs like E-UTRA / LTE; the corresponding CN entities need to be replaced by LTE entities, for example, AMF with MME, g-nodeB with e-nodeB, UDM with HSS, etc. But the principles of the solution remain the same. The network used in this embodiment is explained using any 5G Core Network Function, for example, AMF. However, the network could be any 5G / EUTRAN Core Network Entities like AMF / SMF / MME / UPF, or the network could be any 5G / EUTRAN RAN Entity like eNodeB (eNB) or gNodeB (gNB) or NG-RAN, etc. The messages used or indicated in this embodiment are shown as an example. The messages could be any signaling messages between UE and the Network Functions / Entities or between different Network functions / entities.

[0125] The terms camp and register are used interchangeably and have the same meaning. The terms wait timer, Discontinuous Coverage (DisCo) wait timer, Discontinuous Coverage wait timer, Random timer, Random wait timer, DCW Timer are all used interchangeably and have the same meaning. The terms wait range, Disco Wait Range, Discontinuous Coverage Wait Range, and DCW Range are all used interchangeably and have the same meaning. The term area as used in this embodiment may refer to any of cell / cell ID, TAC / TAI, PLMN, MCC / MNC, latitude / longitude, any CAG / CAG identifier, or any geographical location / coordinate. For the list of possible NAS messages, please refer to 3GPP TS 24501 or 3GPP TS 24301. For the list of AS messages, please refer to 3GPP TS 38331 or 3GPP TS 36331. The cause names in this embodiment are for illustration purposes and can have any name. The non-access stratum (NAS) messages and access stratum (AS) messages described in this embodiment are only for illustration purposes; they can be any NAS or AS messages as per the defined protocol between UE and AMF / MME or UE and gNB (NG-RAN / any RAN node) / eNB. In this embodiment, the term Satellite is used interchangeably with 5G or 4G system with satellite access and is used to represent any Satellite(s) or constellation of Satellites(s) or any aerial body / satellite in any of the Satellite orbits (for example, LEO / MEO / GEO / HEO, etc.) or any 5G system with Satellite Access or 4G System with Satellite Access or any RAN Entity or Core Network Entity or any Network Function(s) associated with the Satellite Access / RAT / PLMN / Network.

[0126] Serving satellite: a satellite providing satellite access to a UE. In the case of NGSO (Non-Geostationary Satellite Orbit), the serving satellite is always changing due to the nature of the constellation.

[0127] S&F Satellite operation: in the context of this study, it is an operation mode of a 5G system with satellite access where the 5G system can provide some level of service (in storing and forwarding the data) when satellite connectivity is intermittently / temporarily unavailable, e.g., to provide communication service for UEs under satellite coverage without a simultaneous active feeder link connection to the ground segment.

[0128] S&F data retention period: it is the data storage validity period for the 5G system with satellite access supporting store and forward operation (e.g., after which undelivered data stored is being discarded).

[0129] UE-Satellite-UE Communication for the 5G system with satellite access: it refers to the communication between UEs under the coverage of one or more serving satellites using satellite access without going through the ground segment.

[0130] The UE context in this embodiment is at least one of the below Field(s):

[0131]

[0132]

[0133]

[0134]

[0135]

[0136]

[0137]

[0138]

[0139] The fifth generation (5G) or 4G System with Satellite access may support Store and Forward mechanism (i.e., S / F operating mode or mechanism) when the feeder link is not available for the serving satellite at the current UE location. The problem statement is explained in the context of multiple satellites serving a UE on the ground. All the satellites will support and operate in S&F mode of operation. Under the above consideration, a UE will try to register or perform a NAS procedure with the core network (NW) (in this version of embodiment core NW will refer to both 4GS & 5GC) by accessing one satellite at a time. But because of the mobility of a satellite in its orbit, a UE might not be able to complete its registration or other NAS procedure while accessing the same satellite. Under such limitation, a UE might need to access another satellite that will serve the UE and assist the UE in completing such NAS procedure with the core NW. The above is just one example and is not limited to only 2 satellite cases, but a UE might need the assistance of multiple satellite accesses (1 at a time) to complete its NAS procedure with the core NW. To allow the above context, management of the UE across all such satellites is a challenge. Context management of UEs which access multiple satellites for completion of one / multiple NAS procedures needs to be defined. As such, contexts need to be maintained and synced across multiple satellites in an optimized manner.

[0140] Embodiments disclosed herein provide a system and method for UE context management in S&F mode in satellite operation. The ground-based MME which is serving the UE and has the UE context after a new UE context is created / existing context is modified or deleted will sync the UE context with all the MME / AMFs onboard the satellites connected to the ground MME. Not all MME / AMFs onboard the satellites might be connected to the ground-based MME at the same time. The ground-based MME should be able to calculate the time in which all MME / AMFs onboard the satellites will eventually be connected to the ground-based MME. This can be done based on satellite coverage information, ephemeris information, etc. This time or at least a minimum of this time will be provided to the UE through NAS procedure ATTACH or REGISTRATION ACCEPT, for example. The UE will start a timer once indicated by the core NW with the value indicated above. The UE will consider that the NAS procedure is complete, for example, that it is registered due to a registration procedure only after the above-mentioned time has elapsed, i.e., after the timer expiry. This ensures that all possible satellites which can possibly serve the UE have the second UE context and the UE accesses such satellites only when they have the second UE context. The UE will access the network after the timer has expired.

[0141] Embodiments disclosed herein provide a system and method for handling UE context in multiple satellites. The present method includes, upon receiving an attach request message, MME initiates the authentication process for a UE. Following successful authentication and the establishment of a secure communication mode, the MME sends an attach accept message to the UE. Concurrently, the MME transmits store and forward policies to the UE, including a UE context activation timer defining the duration within which the UE should recognize itself as registered with the network i.e the UE can start using the new context provided to the UE in the latest NAS message for e.g. the GUTI, NAS keys or eDRX values or power saving parameters or unavailability period information etc. The MME may issue either an Attach Accept or an Attach Reject message to the UE based on the subscription data associated with the UE. In the scenario where a 5G system onboard a satellite connects to a ground station but encounters difficulty establishing a connection with the UE, the MME-onboard communicates the success or failure of the registration procedure to the MME-ground. Upon successful registration, the MME-onboard synchronizes the UE context with the MME-ground. Following the synchronization, the MME-ground transmits an update location message to the HSS indicating whether the UE authentication was successful or unsuccessful. Additionally, any changes to the UE context in any MME-onboard are synchronized with all other MME-onboards when they reconnect with the ground network. It is crucial to manage this synchronization process to ensure that the transfer of the UE context among satellites does not exceed the UE context activation timer.

[0142] In an embodiment, one or more satellites are integrated with the onboard MME. In a similar manner, the network apparatus is integrated with the ground MME. In an embodiment, the ground MME is used as ground-based MME interchangeably. In an embodiment, the first satellite and satellite_1 are used interchangeably, whereas the second satellite and satellite_2 are used interchangeably. Further the onboard MME and MME onboard are used interchangeably. Similarly, ground MME and MME on ground are used interchangeably. Similarly, on board MME-1 can be interchangeably used as onboard MME associated with the satellite_1 and onboard MME-2 can be interchangeably used as onboard MME associated with the satellite_2.

[0143] Referring now to the drawings and more particularly to FIGS 1 through 13, where similar reference characters denote corresponding features consistently throughout the figure, these are shown preferred embodiments.

[0144] FIG 1 illustrates signaling / data traffic exchange between the UE and the network apparatus under normal / default service according to an embodiment. Under normal service, the signaling and the data traffic exchange between the UE (100) and the network apparatus (105) requires the service link and the feeder links to be active simultaneously so that at the time that the UE (100) interacts over the service link with the satellite network (101), there is a continuous end-to-end connectivity path between the UE (100), the satellite network (101), and the ground station (103).

[0145] FIG. 2 illustrates the end-to-end signaling / data traffic exchange between the UE and the network apparatus through the satellite network in S&F operation mode according to an embodiment. The S&F mode, as illustrated in FIG. 2, shows that the end-to-end exchange of signaling and data traffic is handled as a combination of two steps which are not concurrent in time. In step S201, signaling and data traffic exchange between the UE (100) and the satellite network (101) takes place without the satellite network (101) being simultaneously connected to the ground station (102) (i.e., the satellite is able to operate the service link without an active feeder link connection). Further, the connectivity between the satellite network (101) and the ground station (102) is established so that the communication between the satellite network (101) and the ground station (102) can take place. So the satellite network (101) moves from being connected to the UE (100) as illustrated in step S201 to being connected to the ground station (102) as illustrated in step S202.

[0146] The store and forward satellite operation in a 5G system with satellite access is intended to provide some level of communication service for UEs under satellite coverage with intermittent / temporary satellite connectivity (e.g., when the satellite is not connected via a feeder link or via ISL to the ground network) for delay-tolerant communication service.

[0147] An example of S&F satellite operation is illustrated in FIG. 2 in contrast to what could be considered the current assumption for the normal / default satellite operation of a 5G system with satellite access as shown in FIG. 1. Under normal / default satellite operation mode, signaling and data traffic exchange between a UE with satellite access and the ground network requires the service and feeder links to be active simultaneously so that at the time that the UE interacts over the service link with the satellite, there is a continuous end-to-end connectivity path between the UE, the satellite, and the ground network. In contrast, under S&F satellite operation mode, the end-to-end exchange of signaling / data traffic is now handled as a combination of two steps not concurrent in time (Step A and B in FIG. 2). In Step A, signaling / data exchange between the UE and the satellite takes place without the satellite being simultaneously connected to the ground network (i.e., the satellite is able to operate the service link without an active feeder link connection). In Step B, connectivity between the satellite and the ground network is established so that communication between the satellite and the ground network can take place. So the satellite moves from being connected to the UE in step A to being connected to the ground network in step B.

[0148] The concept of S&F service is widely used in the fields of delay-tolerant networking and disruption-tolerant networking. In the 3GPP context, a service that could be assimilated to an S&F service is SMS, for which there is no need to have end-to-end connectivity between the end-points (e.g., an end-point can be a UE and the other an application server) but only between the end-points and the SMSC, which acts as an intermediate node in charge of storing and relaying. The support of S&F satellite operation is especially suited for the delivery of delay-tolerant / non-real-time IoT satellite services with Non-Geostationary Orbit (NGSO) satellites.

[0149] FIG. 3 is a block diagram that illustrates the hardware components associated with the satellite network communication system (600) for managing the UE context in the S&F mode, according to the embodiments as disclosed herein. The satellite network communication system is associated with but not limited to the network apparatus (400), satellite (500) and the UE.

[0150] FIG. 4a is a block diagram that illustrates the hardware components associated with the UE (300) according to the embodiments as disclosed herein. The UE (300) may include, but not be limited to, a smartphone, a laptop, a tablet, a personal computer (PC), an internet of things device, and the like. As shown, the UE (300) includes a processor (301), a memory (303), an input / output (I / O) interface (302), and an interference processing controller (304) communicatively coupled to the processor (301) and the memory (303). Each component is explained in further detail below.

[0151] The processor (301) communicates with the memory (303), the I / O interface (302), and the UE context management controller (304). The processor (301) is configured to execute instructions stored in the memory (303) and to perform various processes. The processor (301) may include one or a plurality of processors, may be a general-purpose processor such as a central processing unit (CPU), an application processor (AP), or the like, a graphics-only processing unit such as a graphics processing unit (GPU), a visual processing unit (VPU), and / or an artificial intelligence (AI) dedicated processor such as a neural processing unit (NPU).

[0152] The memory (303) includes storage locations to be addressable through the processor (301). The memory (303) is not limited to a volatile memory and / or a non-volatile memory. Further, the memory (303) may include a plurality of computer-readable storage media. The memory (303) may include non-volatile storage elements. For example, non-volatile storage elements may include magnetic hard disks, optical disks, floppy disks, flash memories, or forms of electrically programmable memories (EPROM) or electrically erasable and programmable (EEPROM) memories.

[0153] The I / O interface (302) transmits the information between the memory (403) and external peripheral devices. The peripheral devices are the input-output devices associated with the UE context management controller (304). Further, the UE context management controller (304) communicates with the I / O interface (302) and the memory (303). The UE context management controller (304) may be communicatively coupled to the memory (303) and the processor (301). The UE context management controller (304) is an innovative hardware that is realized through the physical implementation of both analog and digital circuits, including logic gates, integrated circuits, microprocessors, microcontrollers, memory circuits, passive and active electronic components, as well as optical components.

[0154] In an embodiment, the UE context management controller (304) is coupled with the memory (303), a processor (301), and the UE context management controller (304) is configured to store first UE context associated with the first satellite (500a) and send a NAS request message to a first satellite (500) to initiate a Non-Access Stratum (NAS) procedure with a second satellite (500b), wherein the initiation of the NAS procedure changes the UE context from the first UE context to a second UE context. The UE context management controller (304) receives a NAS accept message from the first satellite (500a), wherein the NAS accept message includes a UE context activation timer after which the UE can perform the NAS procedure with the second satellite (500b). Further, the UE context management controller (304) initiates the UE context activation timer upon receiving the NAS accept message, and the UE context management controller (304) determines whether the UE context activation timer is expired and performs the NAS procedure using the second UE context upon expiration of the UE context activation timer.

[0155] In an embodiment, the UE context activation timer includes a time period for synchronizing the second UE context across all onboard MME of the satellite network communication system.

[0156] In an embodiment, the performing by the UE context management controller (304) the NAS procedure allows the UE context management controller (304) to access satellites (500) only when the satellites (500) have the second UE context, thereby optimizing the UE context management in the satellite network communication system operating in the S&F mode.

[0157] Fig. 4b illustrates the hardware components associated with the satellite (500) according to the embodiments as disclosed herein. The Satellite (500) is associated with a processor (501), a memory (503), an I / O interface (502), an onboard MME (505) and a UE context management controller (504) communicatively coupled to the processor (501) the memory (503) and the onboard MME. Each component is explained in further detail below.

[0158] The processor (501) communicates with the memory (503), the I / O interface (502) and the UE context management controller (504). The processor (501) is configured to execute instructions stored in the memory (503) and to perform various processes. The processor (501) may include one or a plurality of processors, may be a general-purpose processor, such as a central processing unit (CPU), an application processor (AP), or the like, a graphics-only processing unit such as a graphics processing unit (GPU), a visual processing unit (VPU), and / or an Artificial intelligence (AI) dedicated processor such as a neural processing unit (NPU).

[0159] The memory (503) includes storage locations to be addressable through the processor (501). The memory (503) is not limited to a volatile memory and / or a non-volatile memory. Further, the memory (503) may include a plurality of computer-readable storage media. The memory (503) may include non-volatile storage elements. For example, non-volatile storage elements may include magnetic hard discs, optical discs, floppy discs, flash memories, or forms of electrically programmable memories (EPROM) or electrically erasable and programmable (EEPROM) memories.

[0160] The I / O interface (502) transmits the information between the memory (403) and external peripheral devices. The peripheral devices are the input-output devices associated with the UE context management controller (504). Further, the UE context management controller (504) communicates with the I / O interface (502) and the memory (503). The UE context management controller (504) may be communicatively coupled to the memory (503) and the processor (501). The UE context management controller (504) is an innovative hardware that is realized through the physical implementation of both analog and digital circuits, including logic gates, integrated circuits, microprocessors, microcontrollers, memory circuits, passive and active electronic components, as well as optical components.

[0161] In an embodiment, the onboard MME (505) includes but not limited to MME, AMF, SMF, UPF and the like. The onboard MME (505) implements the data mobility functionality on the satellite. The onboard MME performs the authentication, session management, paging to notify the incoming data, performs handover management, control Plane signaling and others.

[0162] The UE context management controller (504) stores a first UE context associated with the UE (300) at the satellite (500), wherein the satellite (500) provides communication to the UE (300) within the satellite network communication system. The UE context management controller (504) receives a NAS request message from the UE (300). the UE context management controller (504) creates a second UE context in response to receiving the NAS request message from the UE (300). Further the UE (300) generates a NAS accept message by adding a UE context activation timer that includes a time period for synchronizing the second UE context across the satellite network communication system. Furthermore, the UE context management controller (504) transmits the NAS accept message to the UE (300).

[0163] In an embodiment, the NAS request message includes but not limited to attach request, Tracking Area Update (TAU) request and Service request message. Whereas the NAS accept message includes Attach accept message, NAS accept and Service accept message and others.

[0164] The Fig. 4c illustrates the hardware components associated with the network apparatus (400), according to the embodiments as disclosed herein. The network apparatus (400) includes but not limited to AMF, MME, next-generation Node B (gNB), User Plane Function (UPF) and others. The network apparatus is associated with a processor (401), a memory (403), an I / O interface (402), an onboard MME (405) and a UE context management controller (404). The network apparatus (400) is associated with a processor (401), a memory (403), an I / O interface (402), ground MME (405) and a UE context management controller (404).

[0165] The processor (401) communicates with the memory (403), the I / O interface (402) and the UE context management controller (404). The processor (403) is configured to execute instructions stored in the memory (403) and to perform various processes. The processor (401) may include one or a plurality of processors, may be a general-purpose processor, such as a central processing unit (CPU), an application processor (AP), or the like, a graphics-only processing unit such as a graphics processing unit (GPU), a visual processing unit (VPU), and / or an Artificial intelligence (AI) dedicated processor such as a neural processing unit (NPU).

[0166] The memory (403) includes storage locations to be addressable through the processor (401). The memory (403) is not limited to a volatile memory and / or a non-volatile memory. Further, the memory (403) may include a plurality of computer-readable storage media. The memory (403) may include non-volatile storage elements. For example, non-volatile storage elements may include magnetic hard discs, optical discs, floppy discs, flash memories, or forms of electrically programmable memories (EPROM) or electrically erasable and programmable (EEPROM) memories.

[0167] The I / O interface (402) transmits the information between the memory (403) and external peripheral devices. The peripheral devices are the input-output devices associated with the UE context management controller (504). Further, the UE context management controller (404) communicates with the I / O interface (407) and the memory (403). The UE context management controller (504) may be communicatively coupled to the memory (403) and the processor (501). The UE context management controller (404) is an innovative hardware that is realized through the physical implementation of both analog and digital circuits, including logic gates, integrated circuits, microprocessors, microcontrollers, memory circuits, passive and active electronic components, as well as optical components.

[0168] Further in an embodiment, the ground MME includes, but not limited to Mobility Management Function (MME), Access and Mobility Management Function (AMF), Session Management Function (SMF), User Plane Function (UPF), eNodeB(eNB), g Node B(gNB) and others.

[0169] In an embodiment, the synchronization of the second UE context across the satellite network communication system involves creating by the UE context management controller (404) the first UE context associated with the UE (300) at the network apparatus (400). Further the UE context management controller (404) receives a notification message from the satellite (500). The notification message indicates a change from the first UE context to a second UE context for the UE (300). The satellite (300) provides communication to the UE (300) within the satellite network communication system.

[0170] The UE context management controllers (404) and (504) are innovative hardware component integrated into the UE (200) via processing circuitry, which includes logic gates, integrated circuits, microprocessors, microcontrollers, memory circuits, and various electronic and optical components. These circuits may be on semiconductor chips or substrates like printed circuit boards.

[0171] At least one component of the UE context management controllers (504) and (404) may use an AI / ML model. Functions associated with the AI model are executed through the memory and processor. The processors manage input data processing based on predefined operating rules or AI / ML models stored in volatile and non-volatile memory. These models are created through training or learning processes.

[0172] Learning involves applying a learning process to multiple data sets to develop a desired operating rule or AI / ML model. This can occur within the device or via a separate server / system. The AI / ML model may include multiple neural network layers, each with weight values and layer operations. Examples of neural networks include CNN, DNN, RNN, RBM, DBN, BRDNN, GAN, and deep Q-networks. The learning process trains a target device (e.g., a robot) using various data to enable it to make decisions or predictions. Learning methods include supervised, unsupervised, semi-supervised, and reinforcement learning.

[0173] While FIGS. 3, 4b and 4c illustrate the hardware components of the UE (300), the satellite (500) and the network apparatus (400) respectively, alternative embodiments may include different or additional components. The labels or names of these elements are illustrative and do not limit the invention's scope. Components may also be combined to perform similar functions.

[0174] FIG. 5 is a sequence diagram that illustrates the UE context management in S&F mode in satellite operation according to an embodiment. The figure illustrates a multiple satellite scenario where not all satellites serving the UE have the second / any context of the UE (200). This will impact whether the UE (200) can start sending any UL data, for example, to the core network. The pre-condition is that the UE (200), MME / AMF onboard satellite_1 (201a), MME / AMF onboard satellite_2 (202b), and ground-based MME in network apparatus (202) have the same and second UE context referred to as UE context 1.

[0175] At step S601, the UE (200) transmits the NAS request message (e.g., TAU request message) with satellite_2 (201b) to perform the NAS procedure.

[0176] At step S602, the satellite_2 (201b) transmits the NAS accept message to the UE (200) in response to the NAS request message from the UE (200). Subsequently, the UE (200) and the satellite_2 (201b) are updated with the second UE context, that is, UE-context-2.

[0177] Further, at step S603, the satellite_2 (201b) syncs UE context-2 with the network apparatus (202) associated with the ground-based MME.

[0178] At step S604, the UE (200) performs the NAS procedure or tries to send Up Link (UL) data to satellite_1 (201a).

[0179] At step S605, the NAS procedure fails or is rejected at the satellite_1 (201a) as satellite_1 (201a) does not have the second UE context (i.e., UE-context-2).

[0180] At step S606, the satellite_1 (201a) gets UE context-2 at a later point when the ground MME / AMF gets a chance to sync the context with satellite_1 (201a).

[0181] In the embodiment, the ground-based MME, MME / AMF on the ground are synonymous. Similarly, onboard MME / AMF and onboard MME are synonymous, and onboard eNB / gNB and eNB / gNB onboard are synonymous.

[0182] Fig. 6 is a sequence diagram that illustrates the UE context management in S&F mode in satellite operation according to the embodiments as disclosed herein. To address the problems involved in the existing systems, the present solution provides a method for managing the UE context in the S&F mode in a satellite network communication system. The ground-based MME (405), which is serving the UE (300) and has the UE context after a new UE context is created / existing context is modified or deleted, will sync the UE context with all the MME / AMFs onboard (505) the satellites connected to the ground MME / AMF (405). Not all MME / AMFs onboard (505) the satellites might be connected to the ground-based MME (405) at the same time. The ground-based MME (405) should be able to calculate the time in which all MME / AMFs onboard (505) the satellites will eventually be connected to the ground-based MME (405). This can be done based on satellite coverage information, ephemeris information, etc. This time, or at least the minimum of this time, will be provided to the UE (300) through NAS procedure ATTACH or REGISTRATION ACCEPT, for example. The UE (300) will start the timer once indicated by the onboard MME with the value indicated by the onboard MME (505). The UE (300) will consider that the NAS procedure is complete, for example, that it is registered due to a registration procedure only after the above-mentioned time has elapsed, i.e., after the timer expiry i.e. the UE will start to apply the new UE context and access the network after the timer has expired. This ensures that all possible satellites which can possibly serve the UE (300) have the second context of the UE (300) and the UE (300) accesses such satellites only when they have the second UE context. In this embodiment, the timer is referred to as UE context activation timer or S&F wait timer.

[0183] The solutions have been explained with a 2-satellite case for the sake of simplicity but are not limited to such cases. The pre-condition is that the UE, MME / AMF onboard satellite_1 (501a), MME / AMF onboard satellite_2 (500b), and ground-based MME (405) have the same and second UE context referred to as UE-context-1.

[0184] At step S701, the UE (300) performs NAS procedure, for example, NAS request message with satellite_2 (500b). After this, satellite_2 (500b) and the UE (300) have a new UE context, say UE context-2. I.e., before the onboard-MME / AMF (505) provides NAS accept, it determines if the UE context parameter which has changed needs to be synchronized with ground-MME. If yes, then in NAS accept message, the satellite_2 (500b) provides to the UE (300) the UE context activation timer and indicates those respective IEs separately.

[0185] At step S702, the satellite_2 (500b) transmits the NAS accept message. The onboard MME (505) satellite_2 (500b) gives a UE context activation timer to the UE (300). After this, the satellite_2 (500b) and the UE (300) are updated with the new UE context, say UE context-2. I.e., before the onboard-MME / AMF (505) provides NAS accept, it determines if the UE context parameter which has changed needs to be synchronized with the network apparatus (400) associated with the ground-MME / AMF (405). If yes, then in NAS accept message, the onboard MME (505) provides to the UE (300) the UE context activation timer and indicates those respective IEs.

[0186] At step S703, the UE (300) starts the UE context activation timer and the UE (300) does not include those IEs as part of the UE context till the timer is running. The UE (300) may send NAS complete message (acknowledge) message to AMF / MME-onboard (505) to indicate safe reception of temporary / delay context in the UE (300) or it can be a new indication in any of the NAS messages indicating that the UE (300) has safely received the partial UE context which needs to be applied after the UE context activation timer expires.

[0187] At step S704, the satellite_2 (500b) (onboard MME) (505) syncs the change in the UE context, i.e., the UE context-2 with the network apparatus (400) associated with the ground-based MME (405).

[0188] At step S705, in some time, the network apparatus (400) associated with the ground-based MME (405) syncs the UE context-2 with all the satellites, e.g., satellite_1 (500a). Upon the synchronization of the second UE context (UE context-2) from the network apparatus (400), all the satellites, e.g., satellite_1 (500a), are updated with the second UE context. In general within the timer of UE context action timer all the satellites will have the latest UE context synchronized.

[0189] At step S706, eventually, the UE context timer expires as well. After this, the satellite_1 (500a) has the second UE context as well. i.e., it is assumed that this is the maximum time the network apparatus (400) takes to sync the second UE context across all the onboard MME (505) distributed across different satellites.

[0190] At step S707, the UE (300) performs the NAS procedure or tries to send UL data to the satellite_1 (500a). The UE (300) and the satellite_1 (500a) will use the second UE context available. Further, as the UE context matches in both the UE (300) and the satellite_1 (500a), the NAS procedure is completed successfully as illustrated in step S708.

[0191] For example, in step S702, the UE (300) will store / process the NAS accept message it has received, but for all NAS procedures or data transfer, it considers as if the registration accept message is not received from the satellite_2 (500a). Only after step S706, the UE (300) starts behaving as in case that the registration accept message is received and creates the new context in the UE (300). i.e., NAS accept message / UE configuration update message is applicable from step S706 when the timer expires, even though the UE (300) has sent the response registration complete or UE configuration complete message to the satellite network communication system (600).

[0192] In case that the UE context is modified at the ground-MME / AMF (405), then the ground-MME / AMF (405) syncs the UE context with all the onboard-AMF / MME(s) and it will indicate the last onboard-MME / AMF to deliver the respective information elements (IEs) to the UE (300) to apply immediately.

[0193] FIG. 7 is a sequence diagram that illustrates an example scenario of the UE context management in S&F mode in satellite operation according to the embodiments as disclosed herein. The ground-based MME (405), which is serving the UE (300) and has the UE context after a new UE context is created / existing context is modified or deleted, will sync the UE context with all the MME / AMFs onboard the satellites connected to the ground MME / AMF. Not all MME / AMFs onboard the satellites might be connected to the ground-based MME at the same time. The ground-based MME should be able to calculate the time in which all MME / AMFs onboard the satellites will eventually be connected to the ground-based MME. This can be done based on satellite coverage information, ephemeris information, etc. This time, or at least the minimum of this time, will be provided to the UE (300) through NAS procedure ATTACH or REGISTRATION ACCEPT, for example. The NW will indicate to the UE that this timer is applicable for specific IEs included as part of the NAS procedure and might or might not be applicable to all the IEs. The UE (300) will start the UE context activation timer once indicated by the onboard MME (505) with the value indicated in the context activation timer. The UE (300) will consider that the enforcement of values of particular IEs as part of the NAS procedure can be considered as applied only after the above time has elapsed, i.e., the timer has expired in the UE (300). The UE (300) can consider other IEs for which the onboard MME (505) has indicated no timer to be applicable immediately and can perform only such NAS procedures which are impacted by such timers.

[0194] The pre-condition is that the UE (300), the onboard MME satellite_1 (500a), the onboard MME satellite_2 (500b), and the ground-based MME associated with the network apparatus (400) have the same and second UE context referred to as UE context 1. At step S801, the UE (300) performs NAS procedure, for example, TAU procedure with satellite_2 (500b). At step S802, the NAS accept message is transmitted to the UE (300) with UE context activation timer applicable for specific IEs. After this, the satellite_2 (500b) and the UE (300) have new UE context, for example, UE context-2. At step S803, the UE (300) starts context activation timer for IEs indicated in step S802. The UE (300) applies the second values of the rest of the IEs not included in the NAS message at step S802 immediately. At step S804, the satellite_2 (500b) syncs UE context-2 with the ground-based MME (405) associated with the network apparatus (400).

[0195] At step S805, the ground-based MME syncs the UE context-2 with all the satellites, for example, satellite_1 (501a) as well. At step S806, eventually, the UE context timer expires as well. After this, SAT1 has the second UE context as well. At step S807, all IEs from NAS procedure at step S802 are considered as applied and UE starts using them. UE can perform only such NAS procedures or use IEs in the NAS context after step 2 with SAT2 which are not impacted by the timer indicated or started after step 3. UE can perform all NAS procedures after step 6 / 7. For example, in step 2, IE-1 to IE-8 are indicated as can be applied immediately and IE-9 to IE-11 are indicated as to be applied after UE context activation timer. Thus, UE assumes the IEs IE-1 to IE-8 are part of UE context after step 2 and can use it in the NAS / AS procedure. And after step 7, IE-9 to IE-11 are applicable.

[0196] One or more IEs can have different UE context activation timer values. For example, some IEs can be used immediately (e.g., time duration value is zero or with explicit indication or by not including the UE context activation timer in the respective NAS or AS message) and some other IEs may need some time to synchronize with the ground network (indicated with time duration X minutes). For example, UE can apply active timer immediately but periodic registration timer has to be applied after a certain duration of time. The one or more example IEs are listed below. from the list of IEs are listed in 3GPP TS 2430 / TS 24.501 as part of the NAS messages like Attach accept, TAU accept, service accept or service reject etc. This can be any new existing IE of NAS or AS messages as described in 24501 or 24501 or RAN specs, etc.

[0197] The timers described in this embodiment can be provided by the onboard MME in any of the NAS or AS messages or can be pre-configured in the UE (300) or it can be provided to the UE (300) from the satellite network communication system (600) using data path using protocol data unit (PDU) session or any other methods or it can be a standard timer defined with a standard value or range of the value. It can be configured with minimum value UE (300) should start considering.

[0198] FIG 8 is a sequence diagram that illustrates the UE context management in S&F mode in satellite operation according to the embodiments as disclosed herein.

[0199] The ground-based MME (405) which is serving the UE (300) and has the UE context will assign a context identity (ID) value to the second updated UE context which is created / modified / updated. This context ID will be indicated to the UE (300) through NAS procedure through the satellite currently serving the UE (300). UE context ID can be encoded as a Type 4 or Type 6 Information Element in 3GPP. The context ID will be saved in MME / AMF along with UE (300) credentials, for example, IMSI / Subscriber Permanent Identifier (SUPI). The ground-based MME (405) will also indicate this UE context ID to all the other satellites with which the ground-based MME (405) can sync the UE context with. When the UE (300) performs any NAS procedure, the UE (300) will indicate this UE context ID in the NAS procedure to the serving satellite of the UE (300). In case that the UE context ID does not match the satellite / onboard MME, the satellite will reject the NAS procedure optionally with a back-off timer. This back-off timer can be decided by the satellite or can be decided by the ground-based MME depending on satellite coverage information or ephemeris information or time required for ground-based MME to sync second UE context across all possible serving satellites. The onboard MME associated with the satellite can use existing or new 5GMM cause value to back-off the UE. Once the UE (300) is backed off by the serving satellite, the UE (300) can choose to access the next available satellite providing coverage to the UE (300) indicating the UE context ID again. The UE (300) can access the same satellite that rejected the UE (300) only after back-off timer expiry.

[0200] The pre-condition is that the UE (300), onboard MME satellite_1 (500a), onboard MME satellite_2 (500b), and the ground-based MME (405) have the same and second UE context referred to as the UE context 1.

[0201] At step S901, the UE (300) performs NAS procedure, for example, the UE (300) transmits the NAS request message to the satellite_2 (500b). Further, at step S902, NAS accept message is transmitted from the satellite_2 (500b). The onboard MME satellite_2 (500b) gives the UE context ID to the UE (300), say UE context ID-2. The UE (300) and the satellite_2 (500b) have second UE context-2.

[0202] At step S903, the satellite_2 (500b) syncs UE context-2 with the ground MME / AMF (405) associated with the network apparatus (400). The network apparatus (400) is updated with the second UE context (UE context-2).

[0203] At step S904, the UE (300) starts NAS procedure or sends UL data with UE context-2 to the satellite_1 (500a). The satellite_1 (500a) is not synchronized with the second UE context, i.e., the UE context-2.

[0204] At step S905, the NAS procedure is rejected with optional back-off timer value as the satellite_1 (500a) has the UE context-1. The satellite_2 can optionally give a back-off timer in the reject message. The UE (300) is backed off by the serving satellite (optionally this indicates to the UE (300) when the next serving satellite will be available or till when the current service satellite is not having the second UE context will be available due to which the UE (300) needs to back-off). The UE (300) can choose to access the next available satellite providing coverage to the UE (300) indicating the UE context again. The UE (300) can access the same satellite that rejected the UE (300) only after back-off timer expiry. The UE (300) can choose to perform attach procedure by performing optionally locally detach and enter deregistered state.

[0205] In an embodiment, in case that none of the satellites indicates to the UE (300) that it has the required UE context, then the UE (300) may perform local deregistration and enter deregistered state. The UE (300) determines that none of the satellites are having the UE context if it gets the same reject cause from different satellites for time duration X. The time duration X is configured by the network in any of the NAS / AS messages or pre-configured in UE (ME / USIM). The time duration X indicates the maximum time at a given location (optionally with some delta area to handle any potential error cases) when all the satellites will at least once serve the UE.

[0206] At step S906, eventually the ground MME / AMF (405) syncs the UE context-2 with satellite_1 (500a), after which the satellite_1 (500a) has UE context-2. At step S907, the UE (300) performs the NAS procedure or tries to send the UL data to the satellite_1 (500a) with the UE context-2. At step S908, the NAS procedure accepted is completed successfully.

[0207] In an embodiment, at step S904, the UE (300) can indicate both old and new contexts to the serving satellite. For example, UE context-1 and UE context-2. The onboard MME (505) may determine the UE context it has and process the NAS message. The satellite network communication system (600) may indicate back to the UE (300) the UE context ID it has used to process the NAS message.

[0208] In an embodiment, the onboard MME or ground-based MME can indicate a UE context identifier (e.g., Globally Unique Temporary Identifier (GUTI)) which will help identify the context at networks and UE. For UE-initiated procedures, the UE will indicate this ID to the MME-onboard. The MME-onboard checks if the UE context is of this ID. If yes, then it will process the message; otherwise, it will reject, indicating the UE context is not available with the MME-onboard. It may indicate the time at which the next MME-onboard will be available or cell-id / satellite-id / area identifier, etc., of the next satellite which will serve the UE. The UE will try with the MME-onboard next satellite. The main point is UE context is not impacted because some serving satellites do not have the UE context, which is different from a behavior when UE accesses a network, and if the network indicates it has no UE context, then UE will delete the context, enter deregistered state, and trigger attach procedure.

[0209] FIG. 9 is a sequence diagram that illustrates the UE context management initiated by the network apparatus (400) in S&F mode in the satellite network communication system according to the embodiments as disclosed herein. The solution considers the use case where the UE (300), the onboard MME associated with the satellite_1 (500a), the onboard MME (405) associated with the satellite_2 (500b), and the ground-based MME (405) associated with the network apparatus (400) have the same and second UE context referred to as UE context-1. The UE context has changed at the ground-based MME associated with the network apparatus (400), and say the second UE context is UE context-2. As part of the solution, the ground-based MME (405) can indicate to the UE (300) once all possible serving satellites are synced with the second UE context to indicate to the UE (300) that the UE (300) can now start using the second context. Optionally, the ground MME / AMF (405) or the onboard MME (505) or any other NF or core network element can give the UE context activation timer to the UE (300). The UE (300) can start using the second UE context at least after the duration of the UE context activation timer or S&F wait timer by following the methods as described in the embodiment.

[0210] At step S1001, the UE context is changed, for example, the UE context-1 is changed to the UE context-2 in the ground AMF / MME (405) associated with the network apparatus (400). The network apparatus (400) stores the second UE context, i.e., UE context-2, as illustrated in the figure.

[0211] At step S1002, the change in the UE context (i.e., from the UE context-1 to UE context-2) is sent to other satellites (satellite_1 (500a)) along with the UE context activation timer.

[0212] At step S1003, optionally, the second UE context is delivered to the UE (300) in at least one of the NAS messages like UE configuration command message, DL NAS TRANSPORT message, deregistration request message, etc., along with the UE context activation timer.

[0213] At step S1004, the change in the UE context from UE context-1 to UE context-2 is updated to the other satellites (500) by the network apparatus (400).

[0214] At step S1005, the UE (300) starts the UE context activation timer.

[0215] At step S1006, the change in the UE context is indicated to the UE (300). That is, performing the NAS procedure is not dependent on the UE context activation timer. Once the network apparatus (400) does sync with multiple deployed onboard satellites, it can directly indicate to the UE (300) that it can start using the UE context in the form of one or more IEs or complete NAS message, etc. In summary, the network will indicate to the UE (300) when it can start using the new UE context.

[0216] The network in the embodiment can be the onboard MME or core network elements or ground network function / core network elements and others. The ground network function / core network elements can, at an appropriate time, e.g., when sync with all other entities is completed, indicate to onboard entities to inform the UE (300). Otherwise, the ground network function / core network entities can provide a timer value / time stamp; after that duration or at that time, the onboard entity will inform the UE (300) that the new context is now applicable.

[0217] Optionally, the UE (300) can start using the second UE context after the expiry of the UE context activation timer as illustrated in step S1006.

[0218] In an embodiment, Satellite-1 (500a) and Satellite-2 (500b) are the terms used in the embodiment which represent the onboard network function, e.g., AMF / SMF / UPF / P-GW / S-GW / MME. For example, if it is stated that Satellite-1 (500a) syncs the UE context with the ground-MME / AMF (405), it implies MME-onboard Satellite-1 (500a) syncs the UE context with the ground MME / AMF (405).

[0219] In this embodiment, the terms UE context timer, UE context activation timer, and S&F wait timer are used interchangeably and have the same meaning.

[0220] The need for a UE context activation timer, as discussed in this embodiment, is only for IEs which need to be synchronized with the ground MME.

[0221] In this embodiment, the term IE is used to indicate the information when it will be applied as a UE context in the 5G system (UE core network RAN), but it can be a subset of IE information. The complete list of IE information can be obtained in the 3GPP, i.e., the registration accept message is applied partially immediately, and some parts are applied based on the / at expiry of the UE context activation timer based on the value assigned to it.

[0222] In this embodiment, the UE context can be identified by GUTI / IMSI or any other identifier, i.e., it can act as a UE context identifier.

[0223] In this embodiment, the UE initiates a procedure due to which context on the network side is modified, which is used for illustration purposes. The context may change directly at the network side.

[0224] In this embodiment, the UE context (i.e., all the parameters part of it as described in this embodiment) is shared by onboard-MME with ground-MME. This is just for illustration purposes; this can be done at any time. For example, when the UE triggers the Attach procedure, the onboard-MME executes a few procedures, e.g., identification procedure, and fetches the IMSI or any other necessary UE identifier from the UE. The onboard-MME also assigns a GUTI to the UE; in other words, the onboard-MME creates a temporary / partial UE context. The onboard-MME shares this UE context with the MME-ground. In summary, all the information onboard-MME is aware of will be shared with MME-ground. The MME-ground, when it has executed procedures at the ground network, will push back the UE context with the onboard-MME / onboard NFs of the satellite for further processing of the UE Attach or any other NAS procedure. The ground MME shares back the old context it had received from the onboard-MME-1 to onboard-MME-2, which will contact the UE. For example, the ground MME will share the temporary GUTI (assigned by the onboard MME associated with the satellite_1) or any other parameter of the old UE context to the next onboard-MME-2 (or it can also be onboard MME-1), which will contact the UE and complete the UE procedure because this onboard-MME-2 will use any of the parameters of the old UE context (GUTI).

[0225] In this embodiment, the MME-onboard interacts with MME-ground when the feeder link is available. The MME-onboard interacts with the UE when the service link is available. Both feeder link and service link are not available at the same time for S&F operations.

[0226] FIG. 10 is a sequence diagram that illustrates the scenario of handling the UE context in multi-satellite operation according to an embodiment. The UE context in multi-satellite operation involves managing the state and communication context of the user devices across different satellites in a satellite network. The UE context management is essential for ensuring uninterrupted service and efficient use of resources as the UE (100) moves between satellites and network segments. As the UE moves across different satellite coverage areas (e.g., from one satellite to another), the context information needs to be updated to reflect changes in beam coverage or satellite handover.

[0227] At step S1101, when the 5G system onboard the satellite is serving the UE (100), i.e., the service link is available and feeder link connectivity is not available, the UE sends an attach request to the eNB onboard the satellite, which forwards it to the MME onboard. The request contains UE-Identity (old-GUTI or IMSI) together with other parameters defined in 3GPP. Since the MME onboard (201a) is not connected to the HSS on-ground (203) due to feeder-link unavailability at this point in time, it awaits the availability of the feeder-link before executing step S1102.

[0228] At step S1103, when the satellite_1 (201a) regains feeder-link connectivity, it sends an authentication data / information request to the HSS (203) to retrieve authentication vectors as defined in 3GPP. At step S1104, the HSS (203) responds with the requested information in an authentication data / information response. Since the MME on-board is not connected to the UE due to service-link unavailability at this point in time, it awaits the availability of the service-link before executing the next step.

[0229] At step S1105, when the MME onboard the satellite_1 (201a) regains service-link connectivity, it sends a user authentication request to the UE (200) with an authentication challenge as defined in 3GPP. At step S1106, the UE (200) generates an authentication response and provides the same to the MME onboard associated with the satellite_1 (201a) in a user authentication response message. At step S1107, the MME onboard associated with the satellite_1 (201a) validates the authentication response and determines if the authentication is successful. If yes, it proceeds with the next steps; else, it may send an authentication reject message to the UE and terminate the attach procedure. Since the MME on-board is not connected to the HSS (203) on-ground due to feeder-link unavailability at this point in time, it awaits the availability of the feeder-link before executing the next step.

[0230] At step S1109, when the satellite_1 (201a) regains feeder-link connectivity, it sends an update location request to the HSS (203) to indicate it has an authenticated UE (200) and request subscription data of the UE (200). At step S1110, the HSS (203) responds with an update location ack / answer including UE subscription data. This is followed by validation of the UE attach request in the serving network against subscription data. Since the MME on-board is not connected to the UE on-ground due to service-link unavailability at this point in time, it awaits the availability of the service-link before executing the next step.

[0231] At step S1111, the service link becomes unavailable between the UE and the satellite_1 (201a), and the UE (200) awaits the availability of the service link. At step S1112, when the satellite_1 (201a) regains service-link connectivity, it sends an attach accept to the UE containing GUTI. At step S1113, the UE responds with an attach complete message.

[0232] The following problem manifests in the above-mentioned call-flow: the attach procedure takes too long to complete as the eNB / MME on-board needs to wait for either feeder-link or service-link availability before executing the next steps. In order to shorten the time it takes for a UE to attach, we need to explore if we can propose new and modify existing procedures such that a NAS procedure does not have to go through such delays due to the absence of simultaneous service link and feeder link availability. A similar problem applies to 5GS too.

[0233] FIG. 11 is a sequence diagram that illustrates the scenario of handling the UE context in multi-satellite operation according to the embodiments as disclosed herein. The following steps are proposed as a solution, assuming that multiple satellites which support store and forward mode, either connected to the same or different MME-ground(s) or ground station(s), can provide services to UEs supporting the store and forward feature. At step S1201, when the 5G system onboard satellite (505) is serving the UE (300), i.e., when the service link is available and feeder link connectivity is not available, if the UE (300) identifies that the current serving cell supports store & forward mode and the UE (300) is allowed to use store and forward, then the UE (300) sends an attach request message to the satellite network communication system (600). The feeder link between the satellite_1 (500a) and the HSS (700) is unavailable as illustrated in step S1202.

[0234] At step S1203, the satellite_1 (500a) sends a NAS message to acknowledge the reception of the attach request.

[0235] At step S1204, when the 5G system onboard the satellite is connected to the ground station but cannot connect to the UE (300) and feeder link connectivity is available, the MME fetches the authentication vector and other details from HSS (700).

[0236] At step S1205, the HSS (700) responds with the authentication data response to the satellite_1 (500a). Further, the service link between the UE (300) and the satellite_1 (500a) becomes unavailable.

[0237] At step S1207, the satellite_1 (500a) sends an update location request to the HSS (700), and the satellite_1 (500a) receives an update location acknowledgment from the HSS (700) as illustrated in step S1208.

[0238] At step S1209, the network apparatus (400) syncs with the UE information it retrieved with the MME-onboard associated with the satellite_2 (500b). For optimization purposes, the MME-onboard can be any MME-onboard which will serve the UE next.

[0239] At step S1211, the UE (300), in response detecting the signal from the same operator is available (i.e., the discontinuous coverage period has ended), re-sends the attach request message. Further, the feeder link between the satellite_1 (500a) and the satellite_2 (500b) becomes unavailable.

[0240] At step S1213, on receiving the attach request message, the satellite_1 (500a) performs authentication of the UE (300), and on successful authentication and security mode procedure, the satellite_1 (500a) will send an ATTACH ACCEPT message to the UE (300). Along with this, the satellite_1 (500a) will also send store and forward policies to the UE (300). In the store and forward policies, the satellite_1 (500a) will also provide a UE context activation timer after which the UE (300) should consider itself registered with the network. The satellite_1 (500a) might send an ATTACH ACCEPT or ATTACH REJECT message to the UE (300) based on the subscription data of the UE (300).

[0241] At step S1214, later when the 5G system onboard the MME of the satellite_1 (500a) is connected to the network apparatus (400) but cannot connect to the UE, the satellite_1 (500a) indicates to the network apparatus (400) if the UE (300) is successfully registered or if the registration procedure was not successful. The satellite_1 (500a) syncs UE context with the network apparatus (400) if a successful registration procedure is achieved.

[0242] At step S1215, the network apparatus (400) sends an update location indicating to HSS (700) that the UE (200) is authenticated successfully or not authenticated successfully.

[0243] At step S1216, when the UE context is created or changed in any of the satellites, this will be synced with all the satellites when they connect with the network apparatus (400). Deployment should handle that this sync of UE context with all satellites should not take more time than the UE context activation timer.

[0244] FIG 12 is a flow diagram that illustrates the method for managing the UE context in the S&F mode in the satellite network communication system according to the embodiments as disclosed herein.

[0245] At step S1301, the satellite (500) is storing the first UE context associated with a UE (300) at the satellite (500), wherein the satellite (500) provides communication to the UE within the satellite network communication system. Further, the satellite (500) receives the NAS request message from the UE (300) as illustrated at step S1302. The method includes creating by the satellite (500) the second UE context in response to receiving the NAS request message as illustrated in step S1303.

[0246] At step S1304, the satellite (500) generates the NAS accept message by adding the UE context activation timer comprising a time period for synchronizing the second UE context across the satellite network communication system. Further, at step S1305, the satellite (500) sends the NAS accept message to the UE (300).

[0247] In an embodiment, the NAS request message comprises at least one of Attach request, Tracking Area Update (TAU) request, and Service request message, and the NAS accept message comprises at least one of attach accept message, TAU accept, and Service accept message.

[0248] In an embodiment, the synchronizing the second UE context across the satellite network communication system includes creating by the network apparatus (400) the first UE context associated with the UE (300) at the network apparatus (400). Further, the network apparatus (400) receives the notification message from the satellite (500) where the notification message indicates a change from the first UE context to a second UE context for the UE (300). The satellite (500) provides communication to the UE (300) within the satellite network communication system. The network apparatus (400) updates the first UE context to reflect the second UE context at the network apparatus (400) in response to the notification message. The network apparatus (400) further synchronizes the updated second UE context across all the satellites (500) by transmitting the updated second UE context to all the satellites (500). The synchronization of the UE context across all the satellites (500) is completed within a predefined time period specified in a UE context activation timer.

[0249] In an embodiment, the satellite (500) is integrated with the onboard MME (505) which is configured to manage and control an interface communication with the onboard MME for interaction between the satellite (500) and the UE (300) and a Non-Access Stratum (NAS) protocol signaling enabling communication and session management between the UEs (300) and a satellite (500) coverage area.

[0250] In an embodiment, the network apparatus (400) is integrated with a ground-based MME (405) which is configured to manage and control an S6a interface for connectivity with a Home Subscriber Server (HSS), an SGd interface for communication with a Short Message Service Gateway Mobile Switching Center (SMS-GMSC), Interworking Mobile Switching Center (IWMSC), or Short Messaging Service (SMS) Router. Further, the ground-based MME (405) is configured to manage a T6a interface for interaction with a Service Capability Exposure Function (SCEF), a T6ai interface for connectivity with an Interworking Function-Service Capability Exposure Function (IWF-SCEF), and an S11 interface for communication with a Serving Gateway (SGW).

[0251] FIG. 13 is a flow diagram that illustrates the method for managing the UE context in the S&F mode in the satellite network communication system according to the embodiments as disclosed herein.

[0252] At step S1401, the UE (300) stores first UE context associated with a first satellite (500). The UE sends the NAS request message to the first satellite (500) where the initiation of the NAS procedure changes the UE context from the first UE context to a second UE context as illustrated at step S1402.

[0253] At step S1403, the UE (300) receives the NAS accept message from the first satellite (500a) wherein the NAS accept message comprises a UE context activation timer after which the UE can perform the NAS procedure with the second satellite (500b). Further, the UE (300) initiates the UE context activation timer upon receiving the NAS accept message with the UE context activation timer as illustrated at step S1404.

[0254] At step S1405, the UE (300) determines whether the UE context activation timer is expired. Further, the UE (300) performs the NAS procedure using the second UE context upon expiration of the UE context activation timer.

[0255] In an embodiment, the UE context activation timer includes the time period for synchronizing the second UE context across all onboard MME of the satellite network communication system.

[0256] In an embodiment, the NAS procedure allows the UE (300) to access satellites (500) only when the satellites (500) have the second UE context, thereby optimizing the UE context management in the satellite network communication system operating in the S&F mode.

[0257] FIG. 14 illustrates a structure of a UE according to an embodiment of the disclosure.

[0258] As shown in FIG. 14, the UE according to an embodiment may include a transceiver 1410, a memory 1420, and a processor 1430. The transceiver 1410, the memory 1420, and the processor 1430 of the UE may operate according to a communication method of the UE described above. However, the components of the UE are not limited thereto. For example, the UE may include more or fewer components than those described above. In addition, the processor 1430, the transceiver 1410, and the memory 1420 may be implemented as a single chip. Also, the processor 1430 may include at least one processor. Furthermore, the UE of FIG. 14 corresponds to the UE of FIG. 1 to FIG. 13, respectively.

[0259] The transceiver 1410 collectively refers to a UE receiver and a UE transmitter, and may transmit / receive a signal to / from a base station or a network entity. The signal transmitted or received to or from the base station or a network entity may include control information and data. The transceiver 1410 may include a RF transmitter for up-converting and amplifying a frequency of a transmitted signal, and a RF receiver for amplifying low-noise and down-converting a frequency of a received signal. However, this is only an example of the transceiver 1410 and components of the transceiver 1410 are not limited to the RF transmitter and the RF receiver.

[0260] Also, the transceiver 1410 may receive and output, to the processor 1430, a signal through a wireless channel, and transmit a signal output from the processor 1430 through the wireless channel.

[0261] The memory 1420 may store a program and data required for operations of the UE. Also, the memory 1420 may store control information or data included in a signal obtained by the UE. The memory 1420 may be a storage medium, such as read-only memory (ROM), random access memory (RAM), a hard disk, a CD-ROM, and a DVD, or a combination of storage media.

[0262] The processor 1430 may control a series of processes such that the UE operates as described above. For example, the transceiver 1410 may receive a data signal including a control signal transmitted by the base station or the network entity, and the processor 1430 may determine a result of receiving the control signal and the data signal transmitted by the base station or the network entity.

[0263] FIG. 15 illustrates a structure of a network entity according to an embodiment of the present disclosure.

[0264] As shown in FIG. 15, the network entity of the present disclosure may include a transceiver 1510, a memory 1520, and a processor 1530. The transceiver 1510, the memory 1520, and the processor 1530 of the network entity may operate according to a communication method of the network entity described above. However, the components of the terminal are not limited thereto. For example, the network entity may include more or fewer components than those described above. In addition, the processor 1530, the transceiver 1510, and the memory 1520 may be implemented as a single chip. Also, the processor 1530 may include at least one processor.

[0265] For example, the network entity of FIG. 15 corresponds to the MME-ground and / or the MME-onboard of the FIG. 1 to FIG. 13.

[0266] The transceiver 1510 collectively refers to a network entity receiver and a network entity transmitter, and may transmit / receive a signal to / from a base station or a UE. The signal transmitted or received to or from the base station or the UE may include control information and data. In this regard, the transceiver 1510 may include a RF transmitter for up-converting and amplifying a frequency of a transmitted signal, and a RF receiver for amplifying low-noise and down-converting a frequency of a received signal. However, this is only an example of the transceiver 1510 and components of the transceiver 1510 are not limited to the RF transmitter and the RF receiver.

[0267] Also, the transceiver 1510 may receive and output, to the processor 1530, a signal through a wireless channel, and transmit a signal output from the processor 1530 through the wireless channel.

[0268] The memory 1520 may store a program and data required for operations of the network entity. Also, the memory 1520 may store control information or data included in a signal obtained by the network entity. The memory 1520 may be a storage medium, such as ROM, RAM, a hard disk, a CD-ROM, and a DVD, or a combination of storage media.

[0269] The processor 1530 may control a series of processes such that the network entity operates as described above. For example, the transceiver 1510 may receive a data signal including a control signal, and the processor 1530 may determine a result of receiving the data signal.

[0270] A method for managing user equipment (UE) context in a Store and Forward (S&F) mode in a satellite network communication system, comprises storing, by a satellite (500), a first UE context associated with a UE (300) at the satellite (500), wherein the satellite (500) provides communication to the UE, receiving, by the satellite (500), a NAS request message from the UE (300), creating, by the satellite (500), a second UE context in response to receiving the NAS request message, generating, by the satellite (500), a NAS accept message by adding a UE context activation timer comprising a time period for synchronizing the second UE context across and sending, by the satellite (500), the NAS accept message to the UE (300).

[0271] wherein the NAS request message comprises at least one of Attach request, Tracking Area Update (TAU) request and Service request message and wherein the NAS accept message comprises at least one of attach accept message, TAU accept and Service accept message.

[0272] wherein synchronizing the second UE context across the satellite network communication system comprising creating, by a network apparatus (400), the first UE context associated with the UE at the network apparatus (400), receiving, by the network apparatus (400), a notification message from the satellite (500), wherein the notification message indicates a change from the first UE context to a second UE context for the UE (300), and wherein the satellite (500) provides communication to the UE within the satellite network communication system, updating, by the network apparatus (400), the first UE context to reflect the second UE context at the network apparatus (400) in response to the notification message and synchronizing, by the network apparatus (400), the updated second UE context across all the satellites (500) by transmitting the updated second UE context to all the satellites (500), wherein the synchronization of the UE context across all the satellites (500) is completed within a predefined time period specified in a UE context activation timer.

[0273] Wherein the satellite (500) is integrated with an onboard MME which is configured to manage and control at least one of i. an interface communication with the onboard MME for interaction between the satellite (500) and the UE (300) and ii. a Non-Access Stratum (NAS) protocol signalling, enabling communication and session management between the UEs (300) and a satellite (500) coverage area.

[0274] Wherein the network apparatus (400) is integrated with a ground-based MME which is configured to manage and control at least one of i. an S6a interface for connectivity with a Home Subscriber Server (HSS), ii. an SGd interface for communication with a Short Message Service Gateway Mobile Switching Center (SMS-GMSC), Interworking Mobile Switching Center (IWMSC), or SMS Router, iii. a T6a interface for interaction with a Service Capability Exposure Function (SCEF), iv. a T6ai interface for connectivity with an Interworking Function-Service Capability Exposure Function (IWF-SCEF) and v. a S11 interface for communication with a Serving Gateway (SGW).

[0275] A method for managing user equipment (UE) context in a Store and Forward (S&F) mode in a satellite network communication system, comprises storing, by a UE (300), a first UE context associated with a first satellite (500), sending, by the UE, a NAS request message to a first satellite (500), wherein initiation of a NAS procedure changes the UE context from the first UE context to a second UE context, receiving, by the UE (300), a NAS accept message from the first satellite (500), wherein the NAS accept message comprises a UE context activation timer after which the UE (300) can perform the NAS procedure with at least one of the first and the second satellites (500), initiating, by the UE (300), the UE context activation timer upon receiving the NAS accept message with the UE context activation timer, determining, by the UE (300), whether the UE context activation timer is expired and performing, by the UE (300), the NAS procedure using the second UE context upon expiration of the UE context activation timer.

[0276] Wherein the UE context activation timer comprising a time period for synchronizing the second UE context across all onboard MME of the satellite network communication system.

[0277] Wherein performing the NAS procedure allows the UE (300) to access satellites (500) only when the satellites (500) have the second UE context, thereby optimizing the UE context management in the satellite network communication system operating in the S&F mode.

[0278] A satellite network communication system (600) for managing UE context in a Store and Forward (S&F) mode, comprising a satellite (500) and a network apparatus (400), wherein the satellite (500) is associated with a memory (503), a processor (501) and a UE context management controller (504) coupled to the memory (503) and the processor (501), wherein the UE context management controller (504) is configured to store a first UE context associated with a UE at the satellite (500), wherein the satellite (500) provides communication to the UE within the satellite network communication system (600), receive a Non Access Stratum (NAS) request message from the UE (300), create a second UE context in response to receiving the NAS request message, generate a NAS accept message by adding a UE context activation timer comprising a time period for synchronizing the second UE context across the satellite network communication system and send the NAS accept message to the UE (300).

[0279] The NAS request message comprises at least one of Attach request, Tracking Area Update (TAU) request and Service request message and wherein the NAS accept message comprises at least one of attach accept message, TAU accept and Service accept message

[0280] The satellite (500) is integrated with the onboard MME (505) which is configured to manage and control at least one of i. an interface communication with the onboard MME (505) for interaction between the satellite (500) and the UE (300); and ii. a Non-Access Stratum (NAS) protocol signalling, enabling communication and session management between the UEs (300) and a satellite (500)'s coverage area.

[0281] The network apparatus (400) comprises a memory (403) that store a first UE context a processor (401), a UE context management controller (404), coupled to the memory (403) and the processor (401), wherein the UE context management controller (404) is configured to create a first UE context associated with the UE at the network apparatus (400), receive a notification message from the satellite (500), wherein the notification message indicates a change from the first UE context to a second UE context for the UE, and wherein the satellite (500) provides communication to the UE (300) within the satellite network communication system, update the first UE context to reflect the second UE context at the network apparatus (400) in response to the notification message and synchronize the updated second UE context across all the satellites (500) by transmitting the updated second UE context to all the satellites (500), wherein the synchronization of the UE context across all the satellites (500) is completed within a predefined time period specified in a UE context activation timer.

[0282] The network apparatus (400) is integrated with a ground-based MME (405) which is configured to manage and control at least one of i. an S6a interface for connectivity with a Home Subscriber Server (HSS), ii. an SGd interface for communication with a Short Message Service Gateway Mobile Switching Center (SMS-GMSC), Interworking Mobile Switching Center (IWMSC), or SMS Router, iii. a T6a interface for interaction with a Service Capability Exposure Function (SCEF), iv. a T6ai interface for connectivity with an Interworking Function-Service Capability Exposure Function (IWF-SCEF) and v. a S11 interface for communication with a Serving Gateway (SGW).

[0283] A UE (300) for managing UE context in a Store and Forward (S&F) mode in a satellite network communication system, comprises a memory (303) that store a first UE context, a processor (301), a UE context management controller (304), coupled to the memory (303) and the processor (301), wherein the UE context management controller (304) is configured to store a first UE context associated with a first satellite (500), send a Non-Access Stratum (NAS) request message to a first satellite (500) to initiate a NAS procedure with a second satellite (500), wherein the initiation of the NAS procedure changes the UE context from the first UE context to a second UE context, receive a NAS accept message from the first satellite (500), wherein the NAS accept message comprises a UE context activation timer after which the UE can perform the NAS procedure with the second satellite (500), initiate the UE context activation timer upon receiving the NAS accept message, determine whether the UE context activation timer is expired and perform the NAS procedure using the second UE context upon expiration of the UE context activation timer.

[0284] The UE context activation timer comprising a time period for synchronizing the second UE context across all onboard MME of the satellite network communication system.

[0285] Performing the NAS procedure allows the UE to access satellites (500) only when the satellites (500) have the second UE context, thereby optimizing the UE context management in the satellite network communication system operating in the S&F mode.

[0286] The foregoing description of the specific embodiments will so fully reveal the general nature of the embodiments herein that others can, by applying current knowledge, readily modify and or adapt for various applications such specific embodiments without departing from the generic concept, and, therefore, such adaptations and modifications are intended to be comprehended within the meaning and range of equivalents of the disclosed embodiments. It is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation. Therefore, while the embodiments herein have been described in terms of preferred embodiments, those skilled in the art will recognize that the embodiments herein can be practiced with modification within the scope of the embodiments as described herein.

Claims

1.A method performed by a first mobility management entity (MME) which is an onboard MME of a satellite in a wireless communication system, the method comprising:receiving, from a user equipment (UE), an attach request message associated with a non stratum access (NAS) procedure; andtransmitting, to the UE, an attach accept message for the attach request message, the attach accept message including a wait timer for a subsequent NAS procedure,wherein the subsequent NAS procedure is performed based on an expiration of the wait timer.2.The method of claim 1, further comprising:transmitting, to a second MME which is a ground MME associated with the first MME, UE context information.3.The method of claim 2, wherein, in case that the UE context information is created or changed, the created or changed UE context information is synced with a plurality of onboard MMEs including the first MME.4.The method of claim 1, wherein the first MME operates in a store and forward (S&F) mode, andwherein the UE is capable of the S&F mode.5.A method performed by a user equipment (UE) in a wireless communication system, the method comprising:transmitting, to a first mobility management entity (MME) which is an onboard MME of a satellite, an attach request message associated with a non stratum access (NAS) procedure; andreceiving, from the first MME, an attach accept message for the attach request message, the attach accept message including a wait timer for a subsequent NAS procedure,wherein the subsequent NAS procedure is performed based on an expiration of the wait timer.6.The method of claim 5, wherein UE context information is forwarded to a second MME which is a ground MME associated with the first MME via the first MME.7.The method of claim 6, wherein, in case that the UE context information is created or changed, the created or changed UE context information is synced with a plurality of onboard MMEs including the first MME.8.The method of claim 5, wherein the first MME operates in a store and forward (S&F) mode, andwherein the UE is capable of the S&F mode.9.A first mobility management entity (MME) which is an onboard MME of a satellite in a wireless communication system, the first MME comprising:a transceiver; anda controller coupled with the transceiver and configured to:receive, from a user equipment (UE), an attach request message associated with a non stratum access (NAS) procedure, andtransmit, to the UE, an attach accept message for the attach request message, the attach accept message including a wait timer for a subsequent NAS procedure,wherein the subsequent NAS procedure is performed based on an expiration of the wait timer.10.The first MME of claim 9, wherein the controller is further configured to:transmit, to a second MME which is a ground MME associated with the first MME, UE context information.11.The first MME of claim 10, wherein, in case that the UE context information is created or changed, the created or changed UE context information is synced with a plurality of onboard MMEs including the first MME.12.The first MME of claim 9, wherein the first MME operates in a store and forward (S&F) mode, andwherein the UE is capable of the S&F mode.13.A user equipment (UE) in a wireless communication system, the UE comprising:a transceiver; anda controller coupled with the transceiver and configured to:transmit, to a first mobility management entity (MME) which is an onboard MME of a satellite, an attach request message associated with a non stratum access (NAS) procedure, andreceive, from the first MME, an attach accept message for the attach request message, the attach accept message including a wait timer for a subsequent NAS procedure,wherein the subsequent NAS procedure is performed based on an expiration of the wait timer.14.The UE of claim 13, wherein UE context information is forwarded to a second MME which is a ground MME associated with the first MME via the first MME.15.The UE of claim 14, wherein, in case that the UE context information is created or changed, the created or changed UE context information is synced with a plurality of onboard MMEs including the first MME.

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