Method and apparatus for handling UE context for satellite communication

Abstract

According to an embodiment of the present disclosure, a method for handling, by a mobility management entity (MME)-ground, a user equipment (UE) context for satellite communication is provided. The method may comprise maintaining a UE context for a UE based on the UE registering with a network entity. The method may comprise identifying at least one first MME-onboard each of which is in a corresponding satellite having possibility to serve the UE. The method may comprise sharing the UE context stored at the MME-ground with the at least one identified first MME-onboard.

Description

METHOD AND APPARATUS FOR HANDLING UE CONTEXT FOR SATELLITE COMMUNICATION

[0001] Embodiments disclosed herein relate to satellite communications, and more particularly to a method and a system for handling a User Equipment (UE) context for satellite communication.

[0002] A Store and Forward (S&F) satellite operation in a fifth generation (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 an Intersatellite Link　(ISL) to a ground network (106)) for delay-tolerant communication service. An example of a "S&F Satellite operation" is illustrated in FIG. 1 and FIG. 2, in contrast to what could be considered the current assumption for a "normal / default satellite operation" of a 5G system with satellite access.

[0003] As shown in FIG. 1 and FIG. 2, under "normal / default Satellite operation" mode, signalling and data traffic exchange between a UE (102) with satellite access and the remote ground network (106) requires the service and feeder links to be active simultaneously, so that, at the time that the UE (102) interacts over the service link with the satellite (104), there is a continuous end-to-end connectivity path between the UE (102), the satellite (104) and the ground network (106). In contrast, under "S&F Satellite operation" mode, the end-to-end exchange of signalling / data traffic is now managed as a combination of two steps notconcurrent in time (steps A and B). In step A, signalling / data exchange between the UE (102) and the satellite (104) takes place, without the satellite (104) being simultaneously connected to the ground network (106) (i.e., the satellite (104) is able to operate the service link without an active feeder link connection). In step B, connectivity between the satellite (104) and the ground network (106) is established so that communication between the satellite (104) and the ground network (106) can take place. So, the satellite (104) moves from being connected to the UE (102) in step A to being connected to the ground network (106) in step B. The concept of "S&F" service is widely used in the fields of delay-tolerant networking and disruption-tolerant networking. In 3rdGeneration Partnership Project (3GPP) context, a service that could be assimilated to an S&F service is Short Message Service (SMS), for which there is no need to have an end-to-end connectivity between the endpoints (for example, an end-point can be the UE (102) and the other an application server) but only between the end-points and a short message service center (SMSC) which acts as an intermediate node in charge of storing and relying. The support of the S&F Satellite operation is especially suited for the delivery of delay-tolerant / non-real-time Internet of Things　(IoT)　satellite services with Non-Geostationary Orbit　(NGSO) satellites.

[0004] Further, the 5G or fourth generation (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 or at least one of the service link and feeder link is not available simultaneously for the serving satellite (104) at the current UE location. However, how the current 5G or 4G System with the satellite access will handle the Store and Forward (S&F) mode or mechanism is not defined and needs to be defined. Moreover, how the network (i.e., 5G or 4G System with Satellite Access) handle the connection management for the UE(s) (102) when the feeder link is not available or at least one of the service link and feeder link is not available simultaneously is not defined and needs to be defined.

[0005] In prior art, the UE (102) registers with static MME entity of the network, so there was one to one relationship. Static MME used to manage the UE context on the network. Thus, the UE (102) can get the services. For NTN, the satellite (104) is not a static entity, it keeps moving around the globe. Also, once the satellite-1 moves away from the UE service area, the satellite-2 will start serving the UE (102) in a given UE location later satellite-3 will serve the UE (102). This implies that all this satellites should have the UE context so that same UE can be serviced. This gives rise for a need of distributed UE context storage across all the MMEs which will serve the UE (102). Such distributed UE context management was not discussed in the prior art.

[0006] Hence, there is a need in the art for solutions which will overcome the above mentioned drawback(s), among others.

[0007] The principal object of embodiments herein is to disclose an architecture for cellular communication networks with satellite access.

[0008] Another object of embodiments herein is to manage a distributed UE context for satellite communication.

[0009] Another object of embodiments herein is to disclose that an architecture option for a new radio (NR) satellite access to support S&F services is defined, there are N Mobility Management Entity (MME) instances called as MME-onboard deployed and one anchor MME-ground.

[0010] Another object of embodiments herein is to disclose that the MME-ground is configured with potential MME-onboard(s) which can serve the UE based on a UE serving area.

[0011] Another object of embodiments herein is to disclose that the MME-ground is an anchor node situated in a ground network which has the UE context. The MME-ground synchronizes the UE context with all the MME-onboard(s).

[0012] Another object of embodiments herein is to disclose that when a procedure is initiated by the UE, the MME-onboard stores a Non Access Stratum (NAS) message received from the UE because there is no feeder link, it is forward to the MME-ground when feeder link is available. The MME-ground executes procedure and creates the UE context. The MME-ground then synchronizes the UE context with all the MME-onboard(s).

[0013] Another object of embodiments herein is to disclose an architecture for cellular communication networks with satellite access, wherein the 5G or 4G system with Satellite access (i.e., the Satellite Network) may support store and forward mechanism (i.e., S&F operating mode or mechanism) when the feeder link is not available or at least one of the service link and the feeder link is not available simultaneously for the serving satellite at the current UE location.

[0014] Another object of embodiments herein is to disclose an architecture for cellular communication networks with satellite access, wherein the satellite network may have e-NodeB (eNB) / g-NodeB (gNB) onboard and / or MME / AMF-Onboard (for 4G / 5G system with Satellite Access) (or similarly gNB and access and mobility management function　(AMF) / User Plane Function (UPF) UPF / any other Network Function or entities onboard for 4G / 5G system with Satellite Access) present onboard the Satellite System (i.e., the serving Satellite).

[0015] Another object of embodiments herein is to disclose an architecture for cellular communication networks with satellite access, wherein the eNB / gNB present on / onboard the Satellite System (for example, eNB-Onboard / gNB-Onboard) shall act as the RAN Entity for the UE and shall provide the RAN capability to the UE, on behalf of the Satellite Network, optionally when the feeder link is available / not available or when at least one of the service link and feeder link is not available simultaneously.

[0016] Another object of embodiments herein is to disclose an architecture for cellular communication networks with satellite access, wherein the MME / AMF-Onboard present on the Satellite System shall act as a temporary MME / AMF or a proxy MME / AMF for the UE, optionally when the feeder link is not available or when the Satellite is not connected to the ground Network or to the MME / AMF on the ground and the MME / AMF-Onboard may provide Store and Forward functionalities for the UE and may also provide some / all EMM Connection Management Procedures (S1 mode only) like Service Request Procedure (i.e., to support to bring the UE into CM-CONNECTED mode), paging procedure, Transport of NAS messages, generic transport of NAS messages and other similar procedures.

[0017] Another object of embodiments herein is to disclose an architecture for cellular communication networks with satellite access, wherein the MME / AMF-Onboard may be connected to the MME / AMF (on ground) via the existing S10 interface or a new interface (Sxx) may be supported to connect MME / AMF-Onboard with the MME / AMF (on ground) for information / message transfer, wherein the New Interface (Sxx) may have some additional security protection for secure exchange of information / messages between MME / AMF-Onboard and the MME / AMF (on ground) and the MME / AMF-Onboard may forward the messages / information from / for the UE to the MME / AMF (on ground), optionally when feeder link is available, and vice-versa, without any additional security protection.

[0018] Another object of embodiments herein is to disclose an architecture for cellular communication networks with satellite access, wherein the eNB / gNB present on / onboard the Satellite System, if present, may be connected to the MME / AMF-Onboard via the existing S1-MME / AMF interface or a new interface (S1-yy) may be supported to connect MME / AMF-Onboard with the eNB (on board) for information / message transfer, wherein the New Interface (S1-yy) may have some additional security protection for secure exchange of information / messages between MME / AMF-Onboard and the eNB / gNB (OnBoard) and the eNB / gNB-Onboard may forward the messages / information from / for the UE to the MME / AMF-OnBoard, optionally when feeder link is not available, and vice-versa, without any additional security protection.

[0019] 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 should be understood, however, that the following descriptions, while indicating at least one embodiment and numerous specific details thereof, are given by way of illustration and not of limitation. Many changes and modifications may be made within the scope of the embodiments herein without departing from the spirit thereof, and the embodiments herein include all such modifications.

[0020] According to an embodiment of the present disclosure, a method for handling, by a mobility management entity (MME)-ground, a user equipment (UE) context for satellite communication is provided. The method may comprise maintaining a UE context for a UE based on the UE registering with a network entity. The method may comprise identifying at least one first MME-onboard each of which is in a corresponding satellite having possibility to serve the UE. The method may comprise sharing the UE context stored at the MME-ground with the at least one identified first MME-onboard.

[0021] The MME-ground may support a store and forward service in the satellite communication based on the synchronized UE context.

[0022] The at least one first MME-onboard may be identified based on a location of the UE.

[0023] The UE context, stored at the MME-ground, may be shared in response to determining that a feeder link is established between the MME-ground and the at least one first MME-onboard, where the feeder link is a communication link between a onboard entity of a satellite and a ground network.

[0024] The method may comprise detecting that the UE context has changed from a first UE context to a second UE context. The method may comprise identifying at least one second MME-onboard each of which is in a corresponding satellite having possibility to serve the UE, based on the detection. The method may comprise sharing the second UE context stored at the MME-ground with the at least one identified second MME-onboard.

[0025] The method may comprise detecting a change in a UE serving area. The method may comprise identifying at least one third MME-onboard each of which is in a corresponding satellite having possibility to serve the UE based on the detection. The method may comprise sharing the UE context stored at the MME-ground with the at least one identified third MME-onboard.

[0026] The method may comprise detecting a change in a UE serving area. The method may comprise identifying at least one fourth MME-onboard each of which is in a corresponding satellite having possibility not to serve the UE based on the detection. The method may comprise deleting the UE context shared at the at least one identified fourth MME-onboard.

[0027] A MME-onboard may acts as a slave node to the MME-ground. The MME-ground may have an address of a subset of the at least one MME-onboard. The at least one MME-onboard may serve the UE based on a location of the UE.

[0028] The MME-ground may be an anchor node situated in a ground network which has the UE context. The MME-ground may synchronize the UE context with the at least one first MME-onboard.

[0029] The MME-ground may be locally configured with information that indicates which the MME-onboard will serve in the serving area of the UE (102). The MME-ground may be configured by at least one of: an operations and maintenance (O&M) entity and an Application Function (AF) entity through a service capabilities exposure function (SCEF) path.

[0030] The UE context may be created or changed in the at least one first MME-onboard. The UE context may be synchronized with the at least one first MME-onboard, when the at least one MME-onboard (306) connects with a ground network.

[0031] According to an embodiment of the present disclosure, an apparatus for a mobility management entity (MME)-ground for handling a user equipment (UE) context for satellite communication is provided. The apparatus may comprise memory storing instructions. The apparatus may comprise at least one processor. The instructions, when executed by the at least one processor, may cause the apparatus to maintain a UE context for a UE based on the UE registering with a network entity. The instructions, when executed by the at least one processor, may cause the apparatus to identify at least one first MME-onboard each of which is in a corresponding satellite having possibility to serve the UE. The instructions, when executed by the at least one processor, may cause the apparatus to share the UE context stored at the MME-ground with the at least one identified first MME-onboard.

[0032] According to an embodiment of the present disclosure, a non-transitory computer readable storage medium storing instructions is provided. The instructions, when executed by at least one processor of an apparatus for a mobility management entity (MME)-ground, may cause the apparatus to maintain a UE context for a UE based on the UE registering with a network entity. The instructions, when executed by the at least one processor, may cause the apparatus to identify at least one first MME-onboard each of which is in a corresponding satellite having possibility to serve the UE. The instructions, when executed by the at least one processor, may cause the apparatus to share the UE context stored at the MME-ground with the at least one identified first MME-onboard.

[0033] Embodiments herein 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 following illustration drawings. Embodiments herein are illustrated by way of examples in the accompanying drawings, and in which:

[0034] FIG. 1 and FIG. 2 depict an example of "S&F Satellite operation", according to existing arts;

[0035] FIG. 3 depicts an architecture for enabling operation of cellular communication networks with satellite access, according to embodiments as disclosed herein;

[0036] FIG. 4A and FIG. 4B depicts the process of transferring the UE context, according to embodiments as disclosed herein;

[0037] FIG. 5 shows various hardware components of an MME-ground, according to embodiments as disclosed herein;

[0038] FIG. 6 is a flow chart illustrating a method for handling a UE context for satellite communication, according to embodiments as disclosed herein; and

[0039] FIG. 7 shows an example 4G satellite architecture for distributed UE context management, according to embodiments as disclosed herein.

[0040] Table 1 to Table 9 depict the UE context, wherein at least one of the parameters / fields is stored in the onboard / ground AMF / MME, according to embodiments as disclosed herein.

[0041] 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 detailed in the following description. Descriptions of well-known components and processing techniques are omitted so as to not unnecessarily obscure the embodiments herein. The examples used herein are intended merely to facilitate an understanding of ways in which the embodiments herein may be practiced and to further enable those of skill in the art to practice the embodiments herein. Accordingly, the examples should not be construed as limiting the scope of the embodiments herein.

[0042] The words / phrases "exemplary", "example", "illustration", "in an instance", "and the like", "and so on", "etc.", "etcetera", "e.g.,", "i.e.," are merely used herein to mean "serving as an example, instance, or illustration. Any embodiment or implementation of the present subject matter described herein using the words / phrases "exemplary", "example", "illustration", "in an instance", "and the like", "and so on", "etc.", "etcetera", "e.g.," , "i.e.," is not necessarily to be construed as preferred or advantageous over other embodiments.

[0043] Embodiments herein may be described and illustrated in terms of blocks which carry out a described function or functions.　These blocks, which may be 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 may optionally be driven by a firmware. The circuits may, 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 may 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 may be physically separated into two or more interacting and discrete blocks without departing from the scope of the disclosure.　Likewise, the blocks of the embodiments may be physically combined into more complex blocks without departing from the scope of the disclosure.

[0044] It should be noted that elements in the drawings are illustrated for the purposes of this description and ease of understanding and may not have necessarily been drawn to scale. For example, the flowcharts / sequence diagrams illustrate the method in terms of the steps required for understanding of aspects of the embodiments as disclosed herein. Furthermore, in terms of the construction of the device, one or more components of the device may have been represented in the drawings by conventional symbols, and the drawings may show only those specific details that are pertinent to understanding the present embodiments so as not to obscure the drawings with details that will be readily apparent to those of ordinary skill in the art having the benefit of the description herein. Furthermore, in terms of the system, one or more components / modules which comprise the system may have been represented in the drawings by conventional symbols, and the drawings may show only those specific details that are pertinent to understanding the present embodiments so as not to obscure the drawings with details that will be readily apparent to those of ordinary skill in the art having the benefit of the description herein.

[0045] The accompanying drawings are used to help easily understand various technical features and it should be understood that the embodiments presented herein are not limited by the accompanying drawings. As such, the present disclosure should be construed to extend to any modifications, equivalents, and substitutes in addition to those which are particularly set out in the accompanying drawings and the corresponding description. Usage of words such as first, second, third etc., to describe components / elements / steps is for the purposes of this description and should not be construed as sequential ordering / placement / occurrence unless specified otherwise.

[0046] The embodiments herein achieve a method for handling a UE context for satellite communication. The method includes maintaining, by an MME-ground, a UE context in response to a UE registering with a network entity. Further, the method includes identifying, by the MME-ground, at least one MME onboard in which a satellite serves the UE. Further, the method includes sharing, by the MME-ground, the UE context stored at the MME-ground with the at least one identified MME-onboard. Further, the method includes managing, by the MME-ground, the synchronized UE context on the at least one identified MME-onboard.

[0047] Referring now to the drawings, and more particularly to FIGS. 3 through 7, where similar reference characters denote corresponding features consistently throughout the figures, there are shown embodiments.

[0048] The following abbreviations and definitions have been disclosed herein:

[0049] 3GPP: Third Generation Partnership Project

[0050] 5GC: 5G Core

[0051] 5GCN: 5G Core Network

[0052] 5GMM: 5G Mobility Management

[0053] 5GS: 5G System

[0054] AMF: Access and Mobility Management Function

[0055] AS: Access Stratum

[0056] AUSF: Authentication Server Function

[0057] CAG: Closed access group

[0058] CAG ID: Closed Access Group Identifier

[0059] CU: Centralized Unit

[0060] DC: Discontinuous Coverage

[0061] DisCo: Discontinuous Coverage

[0062] DL: Downlink

[0063] DU: Distributed Unit

[0064] EHPLMN: Equivalent Home Public Land Mobile Network

[0065] EMM: EUTRA Mobility Management

[0066] eNB: Evolved Node-B

[0067] EPS: Evolved Packet System

[0068] eSIM: embedded Subscriber Identity Module

[0069] E-UTRA: Evolved Universal Mobile Telecommunication Access

[0070] EUTRAN: Evolved Universal Mobile Telecommunication Access Network

[0071] FPLMN: Forbidden Public Land Mobile Network

[0072] GEO: Geostationary Orbit

[0073] gNB: Next generation Node-B

[0074] gNB - CU: Next generation Node-B Control Unit

[0075] gNB - DU: Next generation Node-B Distributive Unit

[0076] GPRS: General Packet Radio Service

[0077] HPLMN: Home Public Land Mobile Network

[0078] IAB: Integrated access and backhaul

[0079] IAB-UE: The part of the IAB node that supports the Uu interface towards the IAB-donor or another parent IAB-node (and thus manages the backhaul connectivity with either PLMN or SNPN it is registered with) is referred to as an IAB-UE.

[0080] LEO: Low Earth Orbit

[0081] MCC: Mobile Country Code

[0082] MEO: Medium Earth Orbit

[0083] MME / AMF: Mobility Management Entity

[0084] MNC: Mobile Network Code

[0085] MS: Mobile Station. The present document makes no distinction between MS and UE.

[0086] NAS: Non-Access Stratum

[0087] NG-RAN: Next Generation Radio Access Network

[0088] NPN: Non-Public Networks

[0089] NR: New Radio

[0090] NTN: Non Terrestrial Networks

[0091] NW: Network

[0092] OOS: Out of Service

[0093] PDN: Packet Data Network

[0094] PDU: Packet Data Unit

[0095] PLMN ID: Public Land Mobile Network Identity

[0096] RAT: Radio Access Technology

[0097] RPLMN: Registered Public Land Mobile Network

[0098] RRC: Radio Resource Control

[0099] SAT: Satellite

[0100] Satellite: An artificial body placed in orbit round the earth or moon or another planet in order to collect information or for communication.

[0101] Satellite Constellation: Group of satellites, placed in orbit round the earth or moon or another planet in order to collect information or for communication.

[0102] Service User: An individual who has received a priority level assignment from a regional / national authority (i.e., an agency authorized to issue priority assignments) and has a subscription to a mobile network operator

[0103] SIM: Subscriber Identity Module

[0104] SNPN: Standalone Non-Public Networks

[0105] TAU: Tracking Area Update

[0106] TER: Terrestrial

[0107] TN: Terrestrial Networks

[0108] UCU: UE Configuration Update

[0109] UDM: Unified Data Management Function

[0110] UE: User Equipment

[0111] UL: Uplink

[0112] UPU: UE Parameters Update

[0113] USIM: Universal Subscriber Identification Module

[0114] Uu: The radio interface between the UE and the Node B

[0115] VPLMN: Visited Public Land Mobile Network

[0116] WB-S1 Mode Wide Band with S1 Interface

[0117] Visited PLMN (VPLMN): This is a PLMN different from the HPLMN (if the EHPLMN list is not present or is empty) or different from an EHPLMN (if the EHPLMN list is present).

[0118] 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.

[0119] Available PLMN: PLMN(s) in the given area which is / are broadcasting capability to provide wireless communication services to the UE.

[0120] 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.

[0121] EHPLMN: Any of the PLMN entries contained in the Equivalent HPLMN list.

[0122] 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.

[0123] Home PLMN: This is a PLMN where the MCC and MNC of the PLMN identity match the MCC and MNC of the IMSI.

[0124] 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.

[0125] Registration: This is the process of camping on a cell of the PLMN or the SNPN and doing any necessary LRs.

[0126] UPLMN: PLMN / access technology combination in the "User Controlled PLMN Selector with Access Technology" data file in the SIM (in priority order).

[0127] 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).

[0128] The following are an example list of NAS messages (and not limited to) REGISTRATION REQUEST message; ATTACH REQUEST message; ATTACH ACCEPT message; ATTACH REJECT message; Tracking Area UPDATE Request message; TRACKING AREA UPDATE ACCEPT message; Tracking AREA UPDATE REJECT message; DETACH REQUEST message; DETACH ACCEPT message; DETACH REJECT message; DEREGISTRATION REQUEST message; SERVICE REQUEST message; CONTROL PLANE SERVICE REQUEST; IDENTITY REQUEST; AUTHENTICATION REQUEST; AUTHENTICATION RESULT; AUTHENTICATION REJECT; REGISTRATION REJECT; REGISTRATION ACCEPT; DEREGISTRATION ACCEPT; SERVICE REJECT; SERVICE ACCEPT; UE CONFIGURATION UPDATE command; UE PARAMETERS UPDATE command; and so on.

[0129] The term 5GMM sublayer states in this embodiment are at least one of the below:

[0130] 1) 5GMM-NULL

[0131] 2) 5GMM-DEREGISTERED

[0132] a) 5GMM-DEREGISTERED.NORMAL-SERVICE

[0133] b) 5GMM-DEREGISTERED.LIMITED-SERVICE

[0134] c) 5GMM-DEREGISTERED.ATTEMPTING-REGISTRATION

[0135] d) 5GMM-DEREGISTERED.PLMN-SEARCH

[0136] e) 5GMM-DEREGISTERED.NO-SUPI

[0137] f) 5GMM-DEREGISTERED.NO-CELL-AVAILABLE

[0138] g) 5GMM-DEREGISTERED.eCALL-INACTIVE

[0139] h) 5GMM-DEREGISTERED.INITIAL-REGISTRATION-NEEDED

[0140] 3) 5GMM-REGISTERED-INITIATED

[0141] 4) 5GMM-REGISTERED

[0142] a) 5GMM-REGISTERED.NORMAL-SERVICE

[0143] b) 5GMM-REGISTERED.NON-ALLOWED-SERVICE

[0144] c) 5GMM-REGISTERED.ATTEMPTING-REGISTRATION-UPDATE

[0145] d) 5GMM-REGISTERED.LIMITED-SERVICE

[0146] e) 5GMM-REGISTERED.PLMN-SEARCH

[0147] f) 5GMM-REGISTERED.NO-CELL-AVAILABLE

[0148] g) 5GMM-REGISTERED.UPDATE-NEEDED

[0149] 5) 5GMM-DEREGISTERED-INITIATED

[0150] 6) 5GMM-SERVICE-REQUEST-INITIATED

[0151] In this embodiment, the term EMM sublayer states are at least one of the below:

[0152] 1) EMM-NULL

[0153] 2) EMM-DEREGISTERED

[0154] a) EMM-DEREGISTERED.NORMAL-SERVICE

[0155] b) EMM-DEREGISTERED.LIMITED-SERVICE

[0156] c) EMM-DEREGISTERED.ATTEMPTING-TO-ATTACH

[0157] d) EMM-DEREGISTERED.PLMN-SEARCH

[0158] e) EMM-DEREGISTERED.NO-IMSI

[0159] f) EMM-DEREGISTERED.ATTACH-NEEDED

[0160] g) EMM-DEREGISTERED.NO-CELL-AVAILABLE

[0161] h) EMM-DEREGISTERED.eCALL-INACTIVE

[0162] 3) EMM-REGISTERED-INITIATED

[0163] 4) EMM-REGISTERED

[0164] a) EMM-REGISTERED.NORMAL-SERVICE

[0165] b) EMM-REGISTERED.ATTEMPTING-TO-UPDATE

[0166] c) EMM-REGISTERED.LIMITED-SERVICE

[0167] d) EMM-REGISTERED.PLMN-SEARCH

[0168] e) EMM-REGISTERED.UPDATE-NEEDED

[0169] f) EMM-REGISTERED.NO-CELL-AVAILABLE

[0170] g) EMM-REGISTERED.ATTEMPTING-TO-UPDATE-MM

[0171] h) EMM-REGISTERED.IMSI-DETACH-INITIATED

[0172] 5) EMM-DEREGISTERED-INITIATED

[0173] 6) EMM-TRACKING-AREA-UPDATING-INITIATED

[0174] 7) EMM-SERVICE-REQUEST-INITIATED

[0175] The term RAT as defined in this embodiment can be one of the following: NG-RAN, 5G, 4G, 3G, 2G, EPS, 5GS, NR (NR in unlicensed bands), NR (LEO) satellite access, NR (MEO) satellite access, NR (GEO) satellite access, NR (OTHERSAT) satellite access, NR RedCap, E-UTRA, E-UTRA in unlicensed bands, NB-IoT, WB-IoT, LTE-M, and so on.

[0176] 5GS registration types can be, but not limited to, initial registration, mobility registration updating, periodic registration updating, emergency registration, SNPN onboarding registration, disaster roaming initial registration; disaster roaming mobility registration updating, and so on.

[0177] Not setting the registration type to disaster roaming initial registration or disaster roaming mobility registration updating means 5GS registration type is set to value other than "disaster roaming initial registration" or ""disaster roaming mobility registration updating" at least one of initial registration, mobility registration updating, periodic registration updating, emergency registration, SNPN onboarding registration, and so on.

[0178] 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:

[0179] a. 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);

[0180] b. each PLMN / access technology combination in the "User Controlled PLMN Selector with Access Technology" data file in the SIM (in priority order);

[0181] c. 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);

[0182] d. other PLMN / access technology combinations with received high quality signal in random order; and

[0183] e. other PLMN / access technology combinations in order of decreasing signal quality.

[0184] 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:

[0185] a. either the RPLMN or the Last registered PLMN;

[0186] b. 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);

[0187] c. each PLMN / access technology combination in the "User Controlled PLMN Selector with Access Technology" data file in the SIM (in priority order);

[0188] d. 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);

[0189] e. other PLMN / access technology combinations with received high quality signal in random order; and

[0190] f. other PLMN / access technology combinations in order of decreasing signal quality.

[0191] For a 5G system with satellite access, the 5G system shall support service continuity between NR terrestrial access network and NR satellite access networks owned by the same operator or owned by 2 different operators having an agreement. The NTN and TN could either operate in two different frequency bands (e.g. FR1 vs FR2), or in same frequency band (e.g. FR1 or FR2). The Satellite System or Satellite Access as used or defined in this embodiment is applicable for both 5G system with satellite access and / or 4G system with satellite access or any RAT with satellite access. The terms Satellite 3GPP access, Satellite access, Satellite Access Network, NR Satellite Access Network, Satellite NG-RAN Access Technology and NR Satellite access have been interchangeably used and have the same meaning.

[0192] The methods, issues or solutions disclosed in this embodiment are explained using NR satellite access or Satellite NG-RAN Access Technology as an example and is not restricted or limited to NR Satellite access only. However, the solutions proposed in this embodiment are also applicable for Satellite E-UTRAN access Technology, NB (Narrow Band)-S1 mode or WB(Wide Band)-S1 mode via satellite E-UTRAN access and / or NB-IOT (NarrowBand Internet Of Things) or WB-IOT (WideBand Internet Of Things) Satellite Access / Architecture.

[0193] The solutions which are defined for NR(5GC) are also applicable to legacy RATs like E-UTRA / LTE, the corresponding CN entities needs to be replaced by LTE entities (for e.g. AMF with MME / AMF, g-nodeB with e-nodeB, UDM with HSS etc.). But principles of the solution remains same.

[0194] An example list of NAS messages can be, but not limited to, 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, and so on.

[0195] The Network used in this embodiment is explained using any 5G Core Network Function for e.g. AMF. However, the network could be any 5G / EUTRAN Core Network Entities like AMF / SMF / MME / AMF / UPF or the Network could be any 5G / EUTRAN RAN Entity like eNodeB (eNB) or gNodeB (gNB) or NG-RAN etc.

[0196] The messages used or indicated in this embodiment are shown as an example. The messages could be any signalling messages between UE and the Network Functions / Entities or between different Network functions / entities.

[0197] The term area / location / geographical area are used in this embodiment may refer to any of cell / cell ID, TAC / TAI, PLMN ,MCC / MNC, Latitude / longitude, CAG cell or any geographical location / coordinate.

[0198] The methods, issues or solutions disclosed in this embodiment are explained using NR access or NG-RAN Access Technology as an example and is 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 WB(Wide Band)-S1 mode via E-UTRAN access and / or NB-IOT (NarrowBand Internet Of Things) or WB-IOT (WideBand Internet Of Things) Access / Architecture.

[0199] The solutions which are defined for NR(5GC) are also applicable to legacy RATs like E-UTRA / LTE, the corresponding CN entities needs to be replaced by LTE entities for e.g. AMF with MME / AMF, g-nodeB with e-nodeB, UDM with HSS etc. But principles of the solution remains same.

[0200] The Network used in this embodiment is explained using any 5G Core Network Function (for e.g. AMF). However, the network could be any 5G / EUTRAN Core Network Entities like AMF / SMF / MME / AMF / UPF or the Network could be any 5G / EUTRAN RAN Entity like eNodeB (eNB) or gNodeB (gNB) or NG-RAN etc.

[0201] The messages used or indicated in this embodiment are shown as an example. The messages could be any signalling messages between UE and the Network Functions / Entities or between different Network functions / entities.

[0202] The terms camp and register are used interchangeably and have the same meaning.

[0203] The terms wait timer, DisCo wait timer, Discontinuous Coverage wait timer, Random timer, Random wait timer, DCW Timer are all used interchangeably and have the same meaning.

[0204] The terms wait range, Disco Wait Range, Discontinuous Coverage Wait Range, DCW Range are all used interchangeably and have the same meaning.

[0205] 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.

[0206] For the list of possible NAS messages, please refer to 3GPP TS 24.501 or 3GPP TS 24.301, for list of AS messages please refer to 3GPP TS 38.331 or 3GPP TS 36.331

[0207] The cause names in this embodiment are for illustration purpose and it can have any name. The non access stratum (NAS) messages and access stratum (AS) messages described in this embodiment is only for illustration purpose it can be any NAS or AS messages as per defined protocol between UE and AMF / MME / AMF or UE and gNB (NG-RAN / any RAN node) / eNB.

[0208] 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 ex- 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.

[0209] The terms MME / AMF-Onboard and MME / AMF-lighter are used interchangeably in this embodiment and have the same meaning.

[0210] The terms SAT and Satellite are used interchangeably in this embodiment and have the same meaning.

[0211] a) Serving satellite: A satellite providing the 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.

[0212] b) Store & Forward 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.

[0213] c) 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.

[0214] The MME / AMF-ground acts like an anchor / database and if there is any change in the UE context or UE context is created then MME / AMF-onground will notify the updated UE context to all the MME / AMF(s)-onboard whenever the feeder link is available. i.e. whenever MME / AMF-ground and MME / AMF-onboard can communicate. The UE Context used in this embodiment, can refer to the UE Context stored in the MME / AMF as shown in this embodiment or as defined in 3GPP TS 23.401 (for LTE) or 23.502 (for NR). The Satellite System or Satellite Access as used or defined in this embodiment is applicable for both 5G system with satellite access and / or 4G system with satellite access or any RAT with satellite access. The methods, issues or solutions disclosed herein are explained using E-UTRAN / LTE satellite access or Satellite E-UTRAN Access Technology as an example and is not restricted or limited to E-UTRAN / LTE Satellite access only. However, the solutions proposed in this embodiment are also applicable for Satellite NG-RAN access Technology, NB (Narrow Band)-S1 mode or WB(Wide Band)-S1 mode via satellite E-UTRAN access and / or NB-IOT (NarrowBand Internet Of Things) or WB-IOT (WideBand Internet Of Things) Satellite Access / Architecture. The solutions which are defined for LTE(EPS) are also applicable to Other RATs like NR / NG-RAN / 5G, the corresponding CN entities needs to be replaced by NR entities for e.g. MME with AMF, e-nodeB with g-nodeB, HSS with UDM etc. But principles of the solution remains same. For ex- MME(on Board) can be replaced with AMF (On Board), similarly MME (on ground) can be replaced with AMF (on ground) etc. The Network used in this embodiment is explained using any 4G / LTE Core Network Function for e.g. MME. However, the network could be any 5G / EUTRAN Core Network Entities like AMF / SMF / MME / AMF / UPF or the Network could be any 5G / EUTRAN RAN Entity like eNodeB (eNB) or gNodeB (gNB) or NG-RAN etc.

[0215] The MME functions include: NAS signalling; NAS signalling security; Inter CN node signalling for mobility between 3GPP access networks (terminating S3); UE Reachability in ECM-IDLE state (including control, execution of paging retransmission and optionally Paging Policy Differentiation); Tracking Area list management; Mapping from UE location (e.g. TAI) to time zone, and signalling a UE time zone change associated with mobility, PDN GW and Serving GW selection; MME selection for handovers with MME change; SGSN selection for handovers to 2G or 3G 3GPP access networks; Roaming (S6a towards home HSS); Authentication, Authorization; Bearer management functions including dedicated bearer establishment; Lawful Interception of signalling traffic; Warning message transfer function (including selection of appropriate eNodeB); UE Reachability procedures; Support Relaying function (RN Attach / Detach); Change of UE presence in Presence Reporting Area reporting upon PCC request, in the case of Change of UE presence in Presence Reporting Area reporting, management of Core Network pre-configured Presence Reporting Areas, for the Control Plane CIoT EPS Optimisation:

[0216] a) transport of user data (IP, Non-IP and Ethernet));

[0217] b) local Mobility Anchor point;

[0218] c) header compression (for IP user data);

[0219] d) ciphering and integrity protection of user data;

[0220] e) Lawful Interception of user traffic not transported via the Serving GW (e.g. traffic using T6a).

[0221] The Serving GW and the MME may be implemented in one physical node or separated physical nodes. For CIoT EPS Optimisation, the Serving GW and the MME can be implemented in one physical node (e.g. C-SGN) or separated physical nodes. The C-SGN can also encompass the PDN GW function.

[0222] The MME shall signal a change in the UE Time Zone only in the case of mobility and in the case of UE triggered Service Request, PDN Disconnection and UE Detach. If the MME cannot determine whether the UE Time Zone has changed (for example, the UE Time Zone is not sent by the old MME during MME relocation), the MME should not signal a change in UE Time Zone. A change in the UE Time Zone (caused by a regulatory mandated time change (e.g. daylight saving time or summer time change)) shall not trigger the MME to initiate signalling procedures due to the actual change. Instead, the MME shall wait for the UE's next mobility event or Service Request procedure and then use these procedures to update the UE Time Zone information in the PDN GW.

[0223] The Access and Mobility Management function (AMF) includes the following functionality. Some or all of the AMF functionalities may be supported in a single instance of an AMF: Termination of RAN CP interface (N2), Termination of NAS (N1), NAS ciphering and integrity protection, Registration management, Connection management, Reachability management, Mobility Management, Lawful intercept (for AMF events and interface to LI System), Provide transport for SM messages between UE and SMF, Transparent proxy for routing SM messages, Access Authentication, Access Authorization, Provide transport for SMS messages between UE and SMSF, Security Anchor Functionality (SEAF) as specified in TS 33.501, Location Services management for regulatory services, Provide transport for Location Services messages between UE and LMF as well as between RAN and LMF, EPS Bearer ID allocation for interworking with EPS, UE mobility event notification, S-NSSAIs per TA mapping notification, Support for Control Plane CIoT 5GS Optimisation, Support for User Plane CIoT 5GS Optimisation, Support for restriction of use of Enhanced Coverage, Provisioning of external parameters (Expected UE Behaviour parameters or Network Configuration parameters), Support for Network Slice-Specific Authentication and Authorization, Support for charging, Controlling the 5G access stratum-based time distribution based on UE's subscription data, Controlling the gNB's time synchronization status reporting and subscription, and so on.

[0224] Regardless of the number of Network functions, there is only one NAS interface instance per access network between the UE and the CN, terminated at one of the Network functions that implements at least NAS security and Mobility Management.

[0225] In addition to the functionalities of the AMF described above, the AMF may include the following functionality to support non-3GPP access networks:

[0226] a. Support of N2 interface with N3IWF / TNGF. Over this interface, some information (e.g. 3GPP Cell Identification) and procedures (e.g. Handover related) defined over 3GPP access may not apply, and non-3GPP access specific information may be applied that do not apply to 3GPP accesses.

[0227] b. Support of NAS signalling with a UE over N3IWF / TNGF. Some procedures supported by NAS signalling over 3GPP access may be not applicable to untrusted non-3GPP (e.g. Paging) access.

[0228] c. Support of authentication of UEs connected over N3IWF / TNGF.

[0229] d. Management of mobility, authentication, and separate security context state(s) of a UE connected via a non-3GPP access or connected via a 3GPP access and a non-3GPP access simultaneously.

[0230] e. Support a co-ordinated RM management context valid over a 3GPP access and a Non 3GPP access.

[0231] f. Support dedicated CM management contexts for the UE for connectivity over non-3GPP access.

[0232] g. Determine whether the serving N3IWF / TNGF is appropriate based on the slices supported by the N3IWFs / TNGFs.

[0233] Not all of the functionalities are required to be supported in an instance of a Network Slice.

[0234] In addition to the functionalities of the AMF described above, the AMF may include policy related functionalities as described in clause 6.2.8 of TS 23.503. The AMF uses the N14 interface for AMF re-allocation and AMF to AMF information transfer. This interface may be either intra-PLMN or inter-PLMN (e.g. in the case of inter-PLMN mobility). In addition to the functionality of the AMF described above, the AMF may include the following functionality to support monitoring in roaming scenarios:

[0235] a. Normalization of reports according to roaming agreements between VPLMN and HPLMN (e.g. change the location granularity in a report from cell level to a level that is appropriate for the HPLMN); and

[0236] b. Generation of charging / accounting information for Monitoring Event Reports that are sent to the HPLMN.

[0237] In addition to the functionality of the AMF described above, the AMF may provide support for Network Slice restriction and Network Slice instance restriction based on NWDAF analytics. In addition to the functionalities of the AMF described above, the AMF may provide support for the Disaster Roaming. In addition to the functionalities of the AMF described above, the AMF may also include following functionalities to support Network Slice Admission Control:

[0238] a. Support of NSAC for maximum number of UEs.

[0239] In addition to the functionality of the AMF described above, the AMF may include the following functionality to support SNPNs:

[0240] a. Support for Onboarding of UEs for SNPNs.

[0241] In addition to the functionalities of the AMF described above, the AMF may also include following functionalities to support satellite backhaul:

[0242] a. Support for reporting satellite backhaul category (i.e. GEO, MEO, LEO or OTHERSAT) and its modification based on AMF local configuration to SMF.

[0243] In addition to the functionalities of the AMF described above, the AMF may provide support for Network Slice instance change for PDU sessions.

[0244] In addition to the functionalities of the AMF described above, the AMF may also support functionalities for Partial Network Slice support in a Registration Area.

[0245] In addition to the functionalities of the AMF described above, the AMF may also include functionalities to support NS-AoS not matching deployed Tracking Areas.

[0246] In addition to the functionalities of the AMF described above, the AMF may also include functionalities to support Network Slice Replacement.

[0247] The MME shall signal a change in UE Time Zone only in the case of mobility and in the case of UE triggered Service Request, PDN Disconnection and UE Detach. If the MME cannot determine whether the UE Time Zone has changed (e.g. the UE Time Zone is not sent by the old MME during MME relocation), the MME should not signal a change in UE Time Zone. A change in UE Time Zone caused by a regulatory mandated time change (e.g. daylight saving time or summer time change) shall not trigger the MME to initiate signalling procedures due to the actual change. Instead, the MME shall wait for the UE's next mobility event or Service Request procedure and then use these procedures to update the UE Time Zone information in the PDN GW.

[0248] FIG. 3 depicts an architecture for enabling operation of cellular communication networks with satellite access. The UE (102) can register with the MME / AMF (304), when both service link and feeder link are available. The MME / AMF has configured a Periodic TAU (PTAU) timer such that the UE (102) will always remain registered with the network. The MME / AMF and other Core Network (CN) functions are on ground. When the UE (102) does not see a signal (service link), then the UE (102) is in a discontinuous coverage area, but its registration status is maintained. The MME / AMF should provide a PTAU considering both of this parameters (i.e., considering both feeder link and service link availability). Once the UE (102) departs from its location, it will not have connectivity to ground station (or any Network Functions / Entities on ground). From here / this time onwards, the UE (102) at any point of time either have a service link (from the UE perspective) or a feeder link (from CN perspective) from a given LEO satellite or any NGSO Satellite or any satellite; but not at the same time. The Store and Forward (S / F) functional is required from state "2", optionally till the UE (102) is back to the coverage / area where both the service link and the feeder link is available. The first satellite contacting the UE (102) with the service link will be the first satellite contacting the ground MME / AMF (304) and in a circular mechanism. For more than one satellite, at least the AUSF and the UDM are not over the satellite. The PTAU timer is not related to going to the connected mode anymore, because the UE (102) can get into connected mode, but still it will not restart the timer as ground MME / AMF (304) is not yet synced. When a message is received from the ground MME / AMF (304), the UE (102) can restart the timer. the MME / AMF should consider the delay (due to deliver) + PTAU timer as the value of the timer.

[0249] Synchronizing UE contexts between the satellites: The term ACK (or acknowledgement) in this embodiment should be treated as one of the NAS / AS messages described in TS 24.501 / 24.301 or 36.304 / 38.304. For example, when the UE (102) sends an Attach / TAU request message, the MME-onboard the satellite may send the UE (102) with attach accept or TAU accept with the minimal context MME / AMF is holding. Later, the MME / AMF-onboard (306) will deliver the NAS message to the ground MME / AMF (304). The ground MME / AMF (304) will start executing the procedure and once the procedure is executed, the MME / AMF will provide the attach accept / tau accept / registration accept message (which will have all the contents required by the UE to create the UE context).

[0250] In an embodiment, the term satellite is used which actually represents at least one of the NF or gNB which is onboard from the 3GPP perspective. Thus, for example, when the term indicates that the UE (102) sends data to the satellite, it implies that data is sent to one of NFs or gNB (in general node of 3GPP system), which is onboard of the satellite. Similarly, when the satellite sends the data, it means one of NFs or gNB (in general node of 3GPP system) which is onboard of the satellite sends the data to UE (102) or the NF / 3GPP node at the ground.

[0251] The MME / AMF(s) (i.e., the MME / AMF (on ground)) (304) may be pre-configured or may have an information as to which satellites (i.e., which MME / AMF(s)-OnBoard) (304) will be serving the UE(s) (102) in the given location (for example, with the identifier like satellite ID / MME ID or N2-ID or S1-AP ID etc.). The MME / AMF(on ground) (304) may share / indicate the UE context (for example, required / full UE Context or Lighter UE Context) to the Satellites / MME / AMF(s)-onBoard which may serve the UE (102), optionally at any time or any later time at the present / extrapolated UE location (i.e., for example, based on UE mobility / trajectory pattern). If there is a change in the UE context (for example, due to registration procedure triggered by the UE (102) on the same onboard MME / AMF / satellite or different on-board MME / AMF or satellite) or if the MME / AMF (on ground) determines that there is a change in the stored UE Context, then the MME / AMF (on ground) shall share the updated UE context (for example, required / full UE Context or Lighter UE Context), optionally if the feeder link is available, to the Satellites / MME / AMF(s)-onBoard which may serve the UE, optionally at any time or any later time at the present / extrapolated UE location (i.e., for ex- based on UE mobility / trajectory pattern).

[0252] In an embodiment herein, the MME / AMF (on ground) (304) shall share the updated UE context (for example, required / full UE Context or Lighter UE Context), optionally if the feeder link is available, to the Satellites / MME / AMF(s)-onBoard (306), which may have the Old UE Context and which may serve the UE (102), optionally at any time or any later time at the present / extrapolated UE location (i.e., for ex- based on UE mobility / trajectory pattern). In an embodiment herein, the MME / AMF (on ground) (304) shall share the updated UE context (for example, required / full UE Context or Lighter UE Context) to the Satellites / MME / AMF(s)-onBoard (306), which may serve the UE (102), optionally at any time or any later time at the present / extrapolated UE location (i.e., for ex- based on UE mobility / trajectory pattern), at a later point of time, when the feeder link is available. The Satellites / MME / AMF(s)-OnBoard may store two UE Context(s) (for example, the old UE Context and the updated UE Context) for the same UE(s) for certain time duration, optionally till the UE Context is fully synchronised between the UE(s), and / or serving MME / AMF(s) (on ground) and / or the serving satellite / MME / AMF-OnBoard and / or all the satellites / MME / AMF(s)-OnBoard, which may serve the UE, optionally at any point of time at the present / extrapolated UE location. In general, the MME-onboard / AMF-onboard and the MME-onground / AMF-onground etc will share the context with each other if there is a change and all the NFs (which are on the satellite and on the ground) are expected to have the same context, so that they can serve the UE at the any time.

[0253] A network function instance can be deployed such that several network function instances are present within an NF Set to provide distribution, redundancy and scalability together as a Set of NF instances. The same is also supported for NF Services. This can be achieved when the equivalent NFs and NF Services share the same context data or by Network Function / NF Service Context Transfer procedures. Equivalent Control Plane NFs may be grouped into NF Sets; for example, several SMF / MME / AMF instances are grouped into an MME / AMF / SMF Set. The NFs within a NF Set are interchangeable because they share the same context data, and may be deployed in different locations; for example, different data centres, on the satellite and on the ground station etc.

[0254] In this embodiment, the MME / AMF on-board and the MME / AMF on the ground is used as an example, but this same concept can be applied for any of the network functions (NFs). The list of NFs (for example, SMF / PCF / UDM / AUSF / MME / P-GW / S-GW / HSS / NEF / SCEF) are described in TS 23.501. A Control Plane NF comprises of one or multiple NF Services. Within a NF, a NF service may have multiple instances. These multiple NF Service instances can be grouped into one or more NF Service Sets, if they are interchangeable with each other because they share the same context data. The ground NF (for example, MME / AMF) also can be treated as a UDSF function with whom the UE context data is synchronized by all the NFs onboard the satellite.

[0255] FIG. 4A and FIG. 4B depict the process of transferring the UE context. In step 1a, at Time T0, the MME / AMF-OnBoard (306) may store the UE Context (for ex- required / lighter UE Context) and is serving the UE (i.e. the UE is registered with the network and network is maintaining the UE context). Only Service Link is available and feeder link is not available. In step 1b, the MME / AMF-OnGround (304) may store the UE Context for serving the UE (102). In steps 1c and 1 d, the MME / AMF (on ground) (304) may send / indicate the UE Context (for ex- required / lighter UE Context) to the Satellites / MME / AMF-OnBoard (306), which may serve the UE (102) at any point of time and for which feeder link is available currently (for example, Sat-2 and Sat-3). In step 2, at Time T1, the UE context has changed to the MME / AMF-OnGround (304). In steps 3a and 3b, the MME / AMF (on ground) (304) may send / indicate the updated UE Context (for example, required / lighter UE Context) to the Satellites / MME / AMF-OnBoard (306), which may serve the UE (102) at any point of time and for which feeder link is available currently (for example, Sat-2 and Sat-3).

[0256] In steps 3c and 3d, the MME / AMF(s)-OnBoard (for example, MME / AMF-OnBoard (306) of Satellites Sat-2 and Sat-3) may store the new UE Context and optionally may store the Old UE Context, optionally for serving the UE(s) (102) whenever the service link is available. In step 4, at Time T2, the feeder link is available between Sat-1 and MME / AMF-OnGround (304). In step 4 a, the MME / AMF (on ground) (304) may send / indicate the updated UE Context (for example, required / lighter UE Context) to the Satellites / MME / AMF-OnBoard, which may serve the UE (102) at any point of time (for example, based on UE location) and for which feeder link is available currently (for example, Sat-1). In step 4b, the MME / AMF(s)-OnBoard (306) (for example, MME / AMF-OnBoard (306) of Satellite Sat-1) may store the new UE Context and optionally may store the Old UE Context, optionally for serving the UE(s) whenever the service link is available.

[0257] FIG. 5 shows various hardware components of the MME-ground (304), according to embodiments as disclosed herein. In an embodiment, the MME-ground (304) includes a processor (510), a communicator (520), a memory (530), and a UE context controller (540). The processor (510) is coupled with the communicator (520), the memory (530), and the UE context controller (540).

[0258] In an embodiment, the MME-onboard (306) acts as a slave node to the MME-ground (304), where the MME-ground (304) have an address of a subset of the at least one MME-onboard (306). The at least one MME-onboard (306) serves the UE (102) based on a location of the UE (102).

[0259] Further, the MME-ground (304) is an anchor node situated in the ground network (106) which has the UE context, where the MME-ground (304) synchronizes the UE context with the at least one MME-onboard (306).

[0260] The MME-ground (304) is locally configured with an information or is configured by at least one of: an O&M entity and an AF entity (not shown) through a SCEF path (not shown).

[0261] The UE context controller (540) maintains the UE context in response to the UE registering with the network entity (e.g., eNB, gNB or the like). Further, the UE context controller (540) identifies the at least one MME-onboard (306) in which the satellite (104) serves the UE (102). The at least one MME-onboard (306) is identified based on a location of the UE (102). Further, the UE context controller (540) shares the UE context stored at the MME-ground (304) with the at least one identified MME-onboard (306). The UE context, stored at the MME-ground (304), is shared in response to determining that the feeder link is established between the MME-ground (304) and the at least one MME-onboard (306).

[0262] Further, the UE context controller (540) manages the synchronized UE context on the at least one identified MME-onboard (306).

[0263] In an embodiment, the UE context controller (540) detects that the UE context has changed from a first UE context to a second UE context. Further, the UE context controller (540) identifies the at least one MME-onboard (306) in which the satellite serves the UE based on the detection. Further, the UE context controller (540) shares the second UE context stored at the MME-ground (304) with the at least one identified MME-onboard.

[0264] In another embodiment, the UE context controller (540) detects the change in the UE serving area. Further, the UE context controller (540) identifies the at least one MME-onboard (306) in which the satellite serves the UE based on the detection. Further, the UE context controller (540) shares the UE context stored at the MME-ground (304) with the at least one identified MME-onboard (306).

[0265] In another embodiment, the UE context controller (540) detects the change in the UE serving area. Further, the UE context controller (540) identifies the at least one MME-onboard (306) in which the satellite (104) does not serve the UE (102) based on the detection. Further, the UE context controller (540) deletes the UE context shared at the at least one identified MME-onboard.

[0266] The UE context is created or changed in the at least one MME-onboard (306), where the UE context is synchronized with the at least one MME-onboard, when the at least one MME-onboard (306) connects with a ground network.

[0267] Further, the UE context controller (540) supports the store and forward service in the satellite communication based on the synchronized UE context.

[0268] The UE context controller (540) is 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 may optionally be driven by firmware.

[0269] The processor (510) may include one or a plurality of processors. The one or the 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 AI-dedicated processor such as a neural processing unit (NPU). The processor (510) may include multiple cores and is configured to execute the instructions stored in the memory (530).

[0270] Further, the processor (510) is configured to execute instructions stored in the memory (530) and to perform various processes. The communicator (520) is configured for communicating internally between internal hardware components and with external devices via one or more networks. The memory (530) also stores instructions to be executed by the processor (510). The memory (530) may include non-volatile storage elements. Examples of such 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. In addition, the memory (530) may, in some examples, be considered a non-transitory storage medium. The term "non-transitory" may indicate that the storage medium is not embodied in a carrier wave or a propagated signal. However, the term "non-transitory" should not be interpreted that the memory (530) is non-movable. In certain examples, a non-transitory storage medium may store data that can, over time, change (e.g., in Random Access Memory (RAM) or cache).

[0271] Although FIG. 5 shows various hardware components of the MME-ground (304) but it is to be understood that other embodiments are not limited thereon. In other embodiments, the MME-ground (304) may include less or more number of components. Further, the labels or names of the components are used only for illustrative purposes and does not limit the scope of the invention. One or more components can be combined together to perform the same or substantially similar function in the MME-ground (304).

[0272] FIG. 6 is a flow chart (800) illustrating a method for handling the UE context for satellite communication, according to embodiments as disclosed herein. The operations (602-608) are handled by the UE context controller (540).

[0273] At 602, the method includes maintaining the UE context in response to the UE registering with the network entity. At 604, the method includes identifying the at least one MME-onboard (306) in which the satellite (104) serves the UE (102). The identified at least one MME-onboard (306) may be in a corresponding satellite having possibility ot serve the UE (102) At 806, the method includes sharing the UE context stored at the MME-ground (304) with the at least one identified MME-onboard. At 808, the method may further include managing the synchronized UE context on the at least one identified MME-onboard (306).

[0274] The proposed methods allows the UE (102) to get seamless service from different satellites(or MMEs) in the given area. This results in improving the user experience.

[0275] FIG. 7 shows a 4G satellite architecture for distributed UE context management, according to embodiments as disclosed herein. The MME ground (304) is coupled with the MME onboard (306), where the MME onboard (306) is communicated with E-UTRAN(s) (702a, 702b) or NR or in general RAN network. The MME ground (304) communicates with a SGW (704), a HSS (706), a SMS-GMSC / IWMS C / SMS router (708), IWF-SCEF / SCEF (710), a PC RF (712), a PGW (714) and a DN / CIoT service (716), in general any core network nodes at the ground network.

[0276] The 4G satellite architecture (e.g., split MME architecture) between an onboard satellite and a ground satellite is introduced to support distributed UE context storage so that the store and forward service can be supported using the satellite communication. The MME-ground (304) acts the anchor node and the MME-onboard (306) acts as a slave nodes to the MME-ground (304). The UE context is distributed across all the MME(s). The UE (102) can access any of the MMEs without knowing which MME the UE (102) is accessing to. There can be many MME-onboards of different satellites. The MME-ground (304) have the address of subset of the MME-onboards (306) which will serve the UE (102) based on the location of serving the UE (102). If there is any change in the UE context, the MME-ground (304) is responsible to identify it and sync the UE context on all the MME-onboard (306) which are serving the UE in a given location. If a particular MME-onboard (306) will not serve the UE (102) (for e.g. due to new location of the UE) then the MME-ground (304) should remove the UE context from that particular MME-onboard. The MME-ground (304) is locally configured with an information or is configured by at least one of: an O&M entity and an AF entity (not shown) through a SCEF path (not shown).

[0277] The MME-ground (304) maintains the UE context in response to the UE registering with the network entity (e.g., eNB, gNB or the like). Further, the MME-ground (304) identifies the at least one MME-onboard (306) in which the satellite (104) serves the UE (102). The at least one MME-onboard (306) is identified based on a location of the UE (102). Further, the MME-ground (304) shares the UE context stored at the MME-ground (304) with the at least one identified MME-onboard (306). The UE context, stored at the MME-ground (304), is shared in response to determining that the feeder link is established between the MME-ground (304) and the at least one MME-onboard (306).

[0278] Further, the MME-ground (304) manages the synchronized UE context on the at least one identified MME-onboard (306). In an embodiment, the MME-ground (304) detects that the UE context has changed from a first UE context to a second UE context. Further, the MME-ground (304) identifies the at least one MME-onboard (306) in which the satellite serves the UE based on the detection. Further, the MME-ground (304) shares the second UE context stored at the MME-ground (304) with the at least one identified MME-onboard.

[0279] In another embodiment, the MME-ground (304) detects the change in the UE serving area. Further, the MME-ground (304) identifies the at least one MME-onboard (306) in which the satellite serves the UE based on the detection. Further, the MME-ground (304) shares the UE context stored at the MME-ground (304) with the at least one identified MME-onboard (306).

[0280] In another embodiment, the MME-ground (304) detects the change in the UE serving area. Further, the MME-ground (304) identifies the at least one MME-onboard (306) in which the satellite (104) does not serve the UE (102) based on the detection. Further, the MME-ground (304) deletes the UE context shared at the at least one identified MME-onboard.

[0281] Further, the MME-ground (304) supports the store and forward service in the satellite communication based on the synchronized UE context.

[0282] The wireless network can be, for example, but not limited to a fourth generation (4G) network, a 5G network, a sixth generation (6G) network, ORAN or the like.

[0283] The UE (102) can be, for example, but not limited to a laptop, a desktop computer, a notebook, a Device-to-Device (D2D) device, a vehicle to everything (V2X) device, a smartphone, a foldable phone, a smart TV, a tablet, an immersive device, and an internet of things (IoT) device. The AMF entity has provided S-NSSAI1 into Partially Allowed NSSAI or this S-NSSAI1 is associated with NS-AoS.

[0284] Table 1 to Table 9 depict the UE context, wherein at least one of the parameters / fields is stored in the onboard / ground AMF / MME.

[0285] The embodiment disclosed herein describes an architecture for cellular communication networks with satellite access. Therefore, it is understood that the scope of the protection is extended to such a program and in addition to a computer readable means having a message therein, such computer readable storage means contain program code means for implementation of one or more steps of the method, when the program runs on a server or mobile deviceor any suitable programmable device. The method is implemented in at least one embodiment through or together with a software program written in e.g., Very high speed integrated circuit Hardware Description Language (VHDL) another programming language, or implemented by one or more VHDL or several software modules being executed on at least one hardware device. The hardware device can be any kind of portable device that can be programmed. The device may also include means which could be e.g., hardware means like e.g., an ASIC, or a combination of hardware and software means, e.g. an ASIC and an FPGA, or at least one microprocessor and at least one memory with software modules located therein. The method embodiments described herein could be implemented partly in hardware and partly in software. Alternatively, the invention may be implemented on different hardware devices, e.g., using a plurality of CPUs.

[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 should and 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 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.

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[0288]

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[0290]

[0291]

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[0295]

Claims

1.A method for handling, by a mobility management entity, MME,-ground (304), a user equipment, UE, context for satellite communication, the method comprising:maintaining (602) a UE context for a UE (102) based on the UE (102) registering with a network entity;identifying (604) at least one first MME-onboard (306) each of which is in a corresponding satellite having possibility to serve the UE (102); andsharing (606 ) the UE context stored at the MME-ground (304) with the at least one identified first MME-onboard (306).2.The method of claim 1, wherein the MME-ground (304) supports a store and forward service in the satellite communication based on the synchronized UE context.3.The method of claim 1, wherein the at least one first MME-onboard (306) is identified based on a location of the UE.4.The method of claim 1, wherein the UE context, stored at the MME-ground (304), is shared in response to determining that a feeder link is established between the MME-ground (304) and the at least one first MME-onboard (306), where the feeder link is a communication link between a onboard entity of a satellite (104) and a ground network (106).5.The method of claim 1, further comprising:detecting that the UE context has changed from a first UE context to a second UE context;identifying at least one second MME-onboard each of which is in a corresponding satellite having possibility to serve the UE, based on the detection; andsharing the second UE context stored at the MME-ground (304) with the at least one identified second MME-onboard.6.The method of claim 1, further comprising:detecting a change in a UE serving area;identifying at least one third MME-onboard each of which is in a corresponding satellite having possibility to serve the UE based on the detection; andsharing the UE context stored at the MME-ground (304) with the at least one identified third MME-onboard.7.The method of claim 1, further comprising:detecting a change in a UE serving area;identifying at least one fourth MME-onboard each of which is in a corresponding satellite having possibility not to serve the UE based on the detection; anddeleting the UE context shared at the at least one identified fourth MME-onboard.8.The method of claim 1, wherein a MME-onboard acts as a slave node to the MME-ground (304), wherein the MME-ground (304) have an address of a subset of the at least one MME-onboard, wherein the at least one MME-onboard (306) serves the UE based on a location of the UE.9.The method of claim 1, wherein the MME-ground (304) is an anchor node situated in a ground network which has the UE context, wherein the MME-ground (304) synchronizes the UE context with the at least one first MME-onboard.10.The method of claim 1, wherein the MME-ground (304) is locally configured with information that indicates which the MME-onboard will serve in the serving area of the UE (102) or is configured by at least one of: an operations and maintenance, O&M, entity and an Application Function, AF, entity through a service capabilities exposure function, SCEF, path.11.The method of claim 1, wherein the UE context is created or changed in the at least one first MME-onboard, wherein the UE context is synchronized with the at least one first MME-onboard, when the at least one MME-onboard (306) connects with a ground network.12.An apparatus for a mobility management entity, MME,-ground (304) for handling a user equipment, UE, context for satellite communication, the apparatus comprising:memory (530) storing instructions; andat least one processor (510), wherein the instructions, when executed by the at least one processor (510), cause the apparatus to:maintain a UE context for a UE (120) based on the UE (102) registering with a network entity,identify at least one first MME-onboard (306) each of which is in a corresponding satellite having possibility to serve the UE (102); andshare the UE context stored at the MME-ground (304) with the at least one identified first MME-onboard (306).13.The apparatus of claim 12, wherein the instructions, when executed by the at least one processor (510), cause the apparatus further to be operated according to a method in one of claims 2 to 11.14.A non-transitory computer readable storage medium storing instruction which, when executed by at least one processor (510) of an apparatus for a mobility management entity, MME,-ground (304), cause the apparatus to:maintain a UE context for a UE (120) based on the UE (102) registering with a network entity,identify at least one first MME-onboard (306) each of which is in a corresponding satellite having possibility to serve the UE (102); andshare the UE context stored at the MME-ground (304) with the at least one identified first MME-onboard (306)15.The non-transitory computer readable storage medium of claim 14, wherein the instructions, when executed by the at least one processor (510), cause the apparatus further to be operated according to a method in one of claims 2 to 11.

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