Method and apparatus for handling downlink data during a satellite communication in a wireless communication system

Abstract

The present disclosure relates to a 5G communication system or a 6G communication system for supporting higher data rates beyond a 4G communication system such as long term evolution (LTE). Embodiments herein provide a method and system for handling downlink data or downlink signaling during a satellite communication. The method includes starting a DC maximum time offset timer in response to determining that a DC period has ended during satellite communication. Further, receiving a notification message from a network apparatus over a non-3GPP access. The notification message indicates pending downlink data or downlink signaling over 3GPP access from the network apparatus to a UE. Further, determining whether the maximum time offset timer associated with the UE is running. Further, stopping the maximum time offset timer in response to receiving the notification message, when the maximum time offset timer is determined to be running. In addition, initiating a NAS signaling procedure over 3GPP access for reception of the pending downlink data or downlink signaling from the network apparatus.

Description

METHOD AND APPARATUS FOR HANDLING DOWNLINK DATA DURING A SATELLITE COMMUNICATION IN A WIRELESS COMMUNICATION SYSTEM

[0001] The present disclosure is related to satellite communication. More particularly, the present disclosure is related to a method and system handling downlink data or downlink signaling during a satellite communication.

[0002] Considering the development of wireless communication from generation to generation, the technologies have been developed mainly for services targeting humans, such as voice calls, multimedia services, and data services. Following the commercialization of 5G (5th generation) communication systems, it is expected that the number of connected devices will exponentially grow. Increasingly, these will be connected to communication networks. Examples of connected things may include vehicles, robots, drones, home appliances, displays, smart sensors connected to various infrastructures, construction machines, and factory equipment. Mobile devices are expected to evolve in various form-factors, such as augmented reality glasses, virtual reality headsets, and hologram devices. In order to provide various services by connecting hundreds of billions of devices and things in the 6G (6th generation) era, there have been ongoing efforts to develop improved 6G communication systems. For these reasons, 6G communication systems are referred to as beyond-5G systems.

[0003] 6G communication systems, which are expected to be commercialized around 2030, will have a peak data rate of tera (1,000 giga)-level bit per second (bps) and a radio latency less than 100μsec, and thus will be 50 times as fast as 5G communication systems and have the 1 / 10 radio latency thereof.

[0004] In order to accomplish such a high data rate and an ultra-low latency, it has been considered to implement 6G communication systems in a terahertz (THz) band (for example, 95 gigahertz (GHz) to 3THz bands). It is expected that, due to severer path loss and atmospheric absorption in the terahertz bands than those in mmWave bands introduced in 5G, technologies capable of securing the signal transmission distance (that is, coverage) will become more crucial. It is necessary to develop, as major technologies for securing the coverage, Radio Frequency (RF) elements, antennas, novel waveforms having a better coverage than Orthogonal Frequency Division Multiplexing (OFDM), beamforming and massive Multiple-input Multiple-Output (MIMO), Full Dimensional MIMO (FD-MIMO), array antennas, and multiantenna transmission technologies such as large-scale antennas. In addition, there has been ongoing discussion on new technologies for improving the coverage of terahertz-band signals, such as metamaterial-based lenses and antennas, Orbital Angular Momentum (OAM), and Reconfigurable Intelligent Surface (RIS).

[0005] Moreover, in order to improve the spectral efficiency and the overall network performances, the following technologies have been developed for 6G communication systems: a full-duplex technology for enabling an uplink transmission and a downlink transmission to simultaneously use the same frequency resource at the same time; a network technology for utilizing satellites, High-Altitude Platform Stations (HAPS), and the like in an integrated manner; an improved network structure for supporting mobile base stations and the like and enabling network operation optimization and automation and the like; a dynamic spectrum sharing technology via collision avoidance based on a prediction of spectrum usage; an use of Artificial Intelligence (AI) in wireless communication for improvement of overall network operation by utilizing AI from a designing phase for developing 6G and internalizing end-to-end AI support functions; and a next-generation distributed computing technology for overcoming the limit of UE computing ability through reachable super-high-performance communication and computing resources (such as Mobile Edge Computing (MEC), clouds, and the like) over the network. In addition, through designing new protocols to be used in 6G communication systems, developing mechanisms for implementing a hardware-based security environment and safe use of data, and developing technologies for maintaining privacy, attempts to strengthen the connectivity between devices, optimize the network, promote softwarization of network entities, and increase the openness of wireless communications are continuing.

[0006] It is expected that research and development of 6G communication systems in hyper-connectivity, including person to machine (P2M) as well as machine to machine (M2M), will allow the next hyper-connected experience. Particularly, it is expected that services such as truly immersive eXtended Reality (XR), high-fidelity mobile hologram, and digital replica could be provided through 6G communication systems. In addition, services such as remote surgery for security and reliability enhancement, industrial automation, and emergency response will be provided through the 6G communication system such that the technologies could be applied in various fields such as industry, medical care, automobiles, and home appliances.

[0007] The present disclosure relates to wireless communication systems and, more specifically, the present disclosure relates to apparatus and method for handling downlink data or downlink signaling during a satellite communication in a wireless communication system.

[0008] In one embodiment, the objectives are achieved by providing a method for handling downlink data or downlink signaling during a satellite communication. The method includes starting a DC maximum time offset timer in response to determining that a DC period has ended during satellite communication. Further, the method includes receiving a notification message from a network apparatus over a non-3GPP access. The notification message indicates pending downlink data or downlink signaling over 3GPP access from the network apparatus to the UE. Further, the method includes determining whether the DC maximum time offset timer associated with the UE is running. Further, the method includes stopping the DC maximum time offset timer running for 3GPP access in response to receiving the notification message over the non-3GPP access, when the 0064iscontinuous coverage maximum time offset timer is determined to be running. In addition, the method includes initiating a non-access stratum (NAS) signaling procedure over 3GPP access for reception of the pending downlink data or downlink signaling from the network apparatus.

[0009] In an embodiment, the notification message includes an access type indicator set to 3GPP access.

[0010] In an embodiment, the UE is in the 5GMM-IDLE mode over 3GPP access and the UE is in 5GMM-CONNECTED mode over non-3GPP access.

[0011] In an embodiment, the UE starts the DC maximum time offset timer upon returning in a satellite coverage of a tracking area (TA) in a current registration area after being out of satellite coverage due to the DC and the UE has stored a DC maximum time offset.

[0012] In an embodiment, the UE does not initiate any NAS signaling on a New Radio (NR) satellite access and a public land mobile network (PLMN) while the DC maximum time offset timer is running.

[0013] In another aspect, the objectives are achieved by providing a method for handling downlink data or downlink signaling during a satellite communication. The method includes determining to deliver data to the UE during the DC period. In addition, the method includes transmitting a notification message to the UE over a non-3GPP access. The notification message indicates pending downlink data or downlink signaling from the network apparatus to the UE.

[0014] In an embodiment, the notification message includes an access type indicator set to 3GPP access.

[0015] In an embodiment, the method includes detecting initiation of a NAS signaling procedure from the UE after sending the notification message. In addition, the method includes transmitting the pending downlink data or downlink signaling to the UE after initiation of the NAS signaling procedure.

[0016] In yet another aspect, the objectives are achieved by providing a UE for handling downlink data or downlink signaling during a satellite communication. The UE includes a processor, a memory coupled to the processor, and a first controller communicatively coupled to the memory and the processor. The first controller starts a DC maximum time offset timer in response to determining that a DC period has ended during satellite communication. Further, the first controller receives a notification message from a network apparatus over a non-3GPP access. The notification message indicates pending downlink data or downlink signaling over 3GPP access from the network apparatus to the UE. Further, the first controller determines whether the DC maximum time offset timer associated with the UE is running. Further, the first controller stops the DC maximum time offset timer in response to receiving the notification message when the DC maximum time offset timer is determined to be running. In addition, the first controller initiates a NAS signaling procedure over 3GPP access for reception of the pending downlink data or downlink signaling from the network apparatus.

[0017] In an embodiment, the notification message includes an access type indicator set to 3GPP access.

[0018] In an embodiment, the UE is in the 5GMM-IDLE mode over 3GPP access and the UE is in 5GMM-CONNECTED mode over non-3GPP access.

[0019] In an embodiment, the UE starts the DC maximum time offset timer upon returning in a satellite coverage of a tracking area (TA) in a current registration area after being out of satellite coverage due to the DC and the UE has stored a DC maximum time offset.

[0020] In an embodiment, the UE does not initiate any NAS signaling on a NR satellite access and a public land mobile network (PLMN) while the DC maximum time offset timer is running.

[0021] In yet another aspect, the objectives are achieved by providing a network apparatus for handling downlink data or downlink signaling during a satellite communication. The network apparatus includes a second processor, a second memory coupled to the second processor, and a second controller communicatively coupled to the second memory and the second processor. The second processor determines to deliver data to the UE during the DC period. In addition, the second processor transmits a notification message to the UE over a non-3GPP access. The notification message indicates pending downlink data or downlink signaling from the network apparatus to the UE.

[0022] In an embodiment, the notification message includes an access type indicator set to 3GPP access.

[0023] In an embodiment, the second processor detects initiation of a NAS signaling procedure from the UE after sending the notification message. In addition, the second processor transmits the pending downlink data or downlink signaling to the UE after initiation of the NAS signaling procedure.

[0024] 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 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.

[0025] Aspects of the present disclosure provide efficient communication methods in a wireless communication system.

[0026] 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:

[0027] Fig. 1 is a sequence diagram that illustrates a scenario of the UE not responding to a notification when the wait timer is running.

[0028] Fig. 2 is a sequence diagram that illustrates a scenario of the UE behaviour regarding disco wait range and wait timer.

[0029] Fig. 3 is a block diagram that illustrates a normal / default satellite operation of a 5G system with satellite access.

[0030] Fig. 4 is a block diagram that illustrates S&F satellite operation of a 5G system with satellite access.

[0031] Fig. 5 is a block diagram that illustrates a high-level overview of communication between the satellite and the UE.

[0032] Fig. 6 is a block diagram that illustrates a high-level overview of satellite architecture.

[0033] Fig. 7 is a block diagram of the UE for handling after a DC period has ended during satellite communication.

[0034] Fig. 8 is a block diagram of a network apparatus handling after a DC period has ended during satellite communication.

[0035] Fig. 9 is a sequence diagram that illustrates a scenario of the UE responding to a notification and optionally stopping the wait timer it is running.

[0036] Fig. 10 is a sequence diagram that illustrates a scenario of the UE behaviour regarding disco wait range and wait timer.

[0037] Fig. 11 is a sequence diagram that illustrates attach without a public data network (PDN) connectivity for a single satellite.

[0038] Fig. 12 is a flow diagram that illustrates a method for handling downlink data or downlink signaling during a satellite communication from the UE.

[0039] Fig. 13 is a flow diagram that illustrates a method for handling downlink data or downlink signaling during a satellite communication from the network apparatus.

[0040] Fig. 14 is a block diagram of a terminal (or a user equipment (UE), according to embodiments of the present disclosure;

[0041] Fig. 15 is a block diagram of a base station, according to embodiments of the present disclosure; and

[0042] Fig. 16 is a block diagram of a network entity, according to embodiments of the present disclosure.

[0043] Accordingly, the embodiment herein is to a method for handling downlink data or downlink signaling during a satellite communication. The method comprises starting, by a user equipment (UE) (102), a discontinuous coverage (DC) maximum time offset timer in response to determining that a DC period has ended during satellite communication, receiving, by the UE (102), a notification message from a network apparatus (202) over a non-3GPP access (302), wherein the notification message indicates pending downlink data or downlink signalling over 3GPP access from the network apparatus (202) to the UE (102). The method further comprise determining, by the UE (102), whether the DC maximum time offset timer associated with the UE (102) is running, stopping, by the UE (102), the DC maximum time offset timer in response to receiving the notification message, when the DC maximum time offset timer is determined to be running, and initiating, by the UE (102), a non-access stratum (NAS) signalling procedure over 3GPP access for reception of the pending downlink data or downlink signaling from the network apparatus (202).

[0044] In an embodiment, by the UE, the notification message includes an access type indicator set to 3GPP access.

[0045] In an embodiment, the UE (102) is in a 5GMM-IDLE mode over 3GPP access and the UE (102) is in 5GMM-CONNECTED mode over the non-3GPP access (302).

[0046] In an embodiment, the UE (102) starts the DC maximum time offset timer upon returning in a satellite coverage of a tracking area (TA) in a current registration area after being out of satellite coverage due to the DC and the UE (102) has stored a DC maximum time offset.

[0047] In an embodiment, the UE (102) does not initiate any NAS signalling on a NR satellite access and a public land mobile network (PLMN) while the DC maximum time offset timer is running.

[0048] Accordingly, the embodiment herein is to a method for handling downlink data or downlink signaling during a satellite communication. The method comprises determining, by a network apparatus (202), to deliver data to a User Equipment (UE) (102) during the DC period and transmitting, by the network apparatus (202), a notification message to the UE (102) over a non-3GPP access (302), wherein the notification message indicating pending downlink data or downlink signaling from the network apparatus (202) to the UE (102).

[0049] In an embodiment, the notification message includes an access type indicator set to 3GPP access.

[0050] In an embodiment, the method further comprises detecting, by the network apparatus (202), initiation of a NAS signalling procedure from the UE (102) after sending the notification message and transmitting, by the network apparatus (202), the pending downlink data or downlink signalling to the UE (102) after initiation of the NAS signalling procedure.

[0051] Accordingly, the embodiment herein is to a user equipment (UE) (102) for handling downlink data or downlink signaling during a satellite communication. The UE comprises a processor (104), a memory (106) coupled to the processor (104). Further, the UE comprises a first controller (110) communicatively coupled to the memory (106) and the processor (104). The first controller (110) is further configured to starts a discontinuous coverage (DC) maximum time offset timer in response to determining that a DC period has ended during satellite communication, receives a notification message from a network apparatus (202) over a non-3GPP access (302), wherein the notification message indicates pending downlink data or downlink signalling over 3GPP access from the network apparatus (202) to the UE (102), determines whether the DC maximum time offset timer associated with the UE (102) is running, stops the DC maximum time offset timer in response to receiving the notification message, when the DC maximum time offset timer is determined to be running, and initiates a non-access stratum (NAS) signalling procedure over 3GPP access for reception of the pending downlink data or downlink signaling from the network apparatus (202).

[0052] In an embodiment, by the UE, the notification message includes an access type indicator set to 3GPP access.

[0053] In an embodiment, by the UE, the UE (102) is in a 5GMM-IDLE mode over 3GPP access and the UE (102) is in 5GMM-CONNECTED mode over the non-3GPP access (302).

[0054] In an embodiment, by the UE, the UE (102) starts the DC maximum time offset timer upon returning in a satellite coverage of a tracking area (TA) in a current registration area after being out of satellite coverage due to the DC and the UE (102) has stored a DC maximum time offset.

[0055] In an embodiment, by the UE, the UE (102) does not initiate any NAS signalling on a NR satellite access and a public land mobile network (PLMN) while the DC maximum time offset timer is running.

[0056] Accordingly, the embodiment herein is to provide a network apparatus (202) handling downlink data or downlink signaling during a satellite communication. The network apparatus comprises a second processor (204), a second memory (206) coupled to the second processor (204), and a second controller (210) communicatively coupled to the second memory (206) and the second processor (204). The second controller (210) is futher configured to determines to deliver data to a UE (102) during the DC period, and transmits a notification message to the UE (102) over a non-3GPP access (302), wherein the notification message indicating pending downlink data or downlink signaling from the network apparatus (202) to the UE (102).

[0057] In an embodiment, by the network apparatus (202), the notification message includes an access type indicator set to 3GPP access.

[0058] In an embodiment, by the network apparatus (202), the second controller (210) is further configured to detects initiation of a NAS signalling procedure from the UE (102) after sending the notification message, and transmits the pending downlink data or downlink signalling to the UE (102) after initiation of the NAS signalling procedure.

[0059] 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. Also, the various embodiments described herein are not necessarily mutually exclusive, as some embodiments can be combined with a plurality of 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.

[0060] 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 a plurality of 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., a plurality of 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.

[0061] 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.

[0062] In scenarios involving discontinuous satellite coverage, User Equipment (UEs) may only receive service at particular times and locations influenced by the ongoing movement of satellites or satellite constellations. This limitation means that UEs can access satellite services exclusively during designated intervals. As the UEs navigate through these conditions, they may recognize an impending loss of network coverage based on available coverage data or other indicators such as satellite ephemeris, whether they are in a CONNECTED mode or an IDLE mode. When the UEs anticipate regaining satellite coverage after a specified duration, they may initiate signalling to the Network in response to any uplink traffic or NAS layer signalling. Conversely, if the Network has stored downlink data, it may send a page to the UE upon detecting its return to coverage. Additionally, the Network may activate downlink signalling once it confirms that the UE is back within coverage. Few of the power-saving mechanisms / timers / parameters, but not restricted or limited to only these, are Active Time / MICO mode with Active Time, Extended Connected Time / MICO mode with Extended Connected time, Periodic TAU Timer / Periodic Update Timer, Periodic Registration Timer / Periodic Registration Update Timer, eDRX parameters (such as cycle length).

[0063] In the event that the UE becomes unavailable, it may deactivate the 3GPP access stratum. Typically, the network is configured with a discontinuous coverage (DC) wait range. This means that once the DC period concludes, the UE is expected to initiate a wait timer based on the range set by the network. During this interval, the UE should refrain from initiating any Non-Access Stratum (NAS) signalling. This approach aims to randomize the signalling attempts from various UEs, thereby preventing a surge in load when the signal is detected by all UEs in the vicinity after the unavailability period or DC period has ended.

[0064] In a scenario where the UE has exited a state of the DC and has initiated a wait timer, the network is now able to connect with the UE as it is no longer in a state of service. However, the UE may face challenges in establishing a connection because it has disabled the access stratum on the 3GPP access, which prevents any Non-Access Stratum (NAS) signalling from being initiated. Consequently, while the network is technically capable of delivering downlink data, it will be unable to transmit this data to the UE.

[0065] In conventional methods, if a feeder link is unavailable and the UE is either not registered in a current Tracking Area Identifier (TAI) or has lost its registration or network context, the UE may face challenges in initiating registration or attachment. In situations where the satellite does not possess information about the UE, including its context or subscription details, it becomes crucial to manage any registration or attachment requests received from the UE. Additionally, it is necessary to address the round trip time between the UE and the ground-based Mobility Management Entity (MME) when the UE is situated in an area lacking terrestrial network coverage and the satellite serving the UE does not have an available feeder link.

[0066] Hence, is desirable to address the above mentioned problems and disadvantages or at least provide a useful alternative.

[0067] The principal object of the embodiments herein is to provide methods and systems for handling downlink data or downlink signaling during a satellite communication.

[0068] Yet another object of the embodiments herein is to enable the network to transmit a notification message over non-3GPP access with access type set to 3GPP access.

[0069] Yet another object of the embodiments herein is to enables the UE to stop the DC wait timer and initiate the NAS signaling towards the network upon receiving the notification message over the non 3GPP access.

[0070] Yet another object of the embodiments herein is to provide methods and systems for the satellite to handle the attach request / registration request received from the UE when the satellite does not have UE information / UE context / UE subscription details.

[0071] Yet another object of the embodiments herein is to provide methods and systems for handling a round trip time between the UE and the MME on the ground when the UE is in a location where there is no terrestrial network and the satellite serving the UE has no feeder link available.

[0072] Fig. 1 is a sequence diagram that illustrates a scenario of a UE (102) not responding to a notification when the wait timer is running according to the prior art. As shown in the sequence diagram, the UE (102) is in communication with a network apparatus (202) via a non-3GPP access (302). For instance, the network apparatus (202) may be an access and mobility management function (AMF) or any other network entity. At step 1, the network apparatus (202) determines the "wait range" based on network configuration and sends the "DC wait range or DiscoWait Range (i.e., wait range, it can be any name, e.g., DC maximum time offset) to the UE (102) via the Registration procedure or UE Configuration Update procedure or any other NAS signaling message.

[0073] At step 2, the UE (102) enters DC and starts to search for coverage again when it exits DC, i.e., finds the coverage again option all of the same PLMN / Radio Access Technology (RAT) (optionally also same access type) which configured the DC Wait range. The UE (102) starts a random wait timer ((also called as DC maximum time offset timer) based on the DC wait range provided earlier.

[0074] At step 3, the network apparatus (202) has Downlink (DL) data / DL signaling for the UE at this time when the random wait timer is running at the UE (102). The network triggers a network-initiated service request procedure and sends a Notification message over the non-3GPP access (302) or DL data / signaling to the UE (102). At step 4, the network apparatus (202) sends a notification message over the Non-3GPP access (302) (e.g., through N3IWF) to the UE (102) for the pending DL data / DL signaling. At step 5, during the wait timer duration, the UE (102) does not listen to / respond to the notification message by the network apparatus (202). As a result, important DL signaling / data may be missed by the UE (102) even though the network is at this point not overloaded and is fine to accept the signaling from the UE (102).

[0075] Fig. 2 is a sequence diagram that illustrates a scenario of the UE (102) behaviour regarding disco wait range and wait timer according to the prior art. As shown in the sequence diagram, the UE (102) is in communication with the network apparatus (202). At step 1, the network apparatus (202) provides the DisCo Wait Range to the UE (102) (via Registration procedure or UE Configuration Update procedure or any NAS / AS signaling)

[0076] At step 2, the UE (102) calculates the "wait timer" based on "Disco Wait Range" configuration from the network apparatus (202) (e.g. by selecting a random value between 0 and "Disco Wait Range"). Optionally, the UE (102) stores / saves the Disco Wait Range and / or wait timer information / configuration in the UE (102) (ME or USIM or eSIM)

[0077] At step 3, the DC is detected in the current geographic area and the UE (102) enters the DC.

[0078] At step 4, when the UE (102) detects the DC ends, the UE (102) starts the wait timer.

[0079] At step 5, the UE (102) or the upper layers performs any of the following:

[0080] - Switch-Off and optionally Switch-ON i.e. the UE (102) has changed 5GMM sublayer states from 5GMM-REGISTERED to 5GMM-DEREGISTERED or vice versa.

[0081] - SIM / USIM Removal and optionally same / new SIM / USIM insertion

[0082] - SIM / USIM / eSIM has changed i.e. new SIM / USIM / eSIM is inserted

[0083] - The UE (102) selects alternate RAT / PLMN / Access / Network

[0084] - SUPI in SIM / USIM / eSIM has changed

[0085] The UE (102) behaviour regarding DisCo Wait Range and wait timer in these situations is not defined and needs to be defined.

[0086] Fig. 3 is a block diagram that illustrates a normal / default satellite operation of a 5G system with satellite access according to the prior art. Fig. 3 is a block diagram that illustrates S&F satellite operation of a 5G system with satellite access according to the prior art. As shown, the block diagram includes the UE (102), a satellite (402), a ground network (404), and an external network (406). In the existing systems, both the service link (refer to Step A) and the feeder link (refer to Step B) are simultaneously operational. For instance, connections from the UE (102) to the Next generation Node-B (gNB) and from the gNB to the core network are consistently active, facilitating ongoing communication. However, in the case of the S&F service, when the satellite (402) is engaged with the UE (102) (as illustrated in Step A), it is unable to establish communication with the ground network (404) due to the absence of a direct connection. For example, if the UE (102) is located in a remote oceanic area, the satellite (402) captures the signal from the UE (102) and temporarily stores it while traveling towards the vicinity of the ground network (404), which may take several hours. Subsequently, the satellite (402) establishes communication with the ground network (404), such as an application server, and transmits the stored signal from the UE (102).

[0087] 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 (402) is not connected via a feeder link or via ISL to the ground network) for delay-tolerant communication service.

[0088] An example of S&F Satellite operation is illustrated in Fig. 4 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. 4. Under normal / default Satellite operation mode, signaling and data traffic exchange between the UE (102) with satellite access and the ground network (404) 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 (402), there is a continuous end-to-end connectivity path between the UE (102), the satellite (402), and the ground network (404). 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. 4). In Step A, signaling / data exchange between the UE (102) and the satellite (402) takes place without the satellite (402) being simultaneously connected to the ground network (404) (for example, the satellite (402) is able to operate the service link without an active feeder link connection). In Step B, connectivity between the satellite (402) and the ground network (404) is established so that communication between the satellite (402) and the ground network (404) can take place. So the satellite (402) moves from being connected to the UE (102) in step A to being connected to the ground network (404) in step B.

[0089] The concept of S&F service is widely used in the fields of delay-tolerant networking and disruption-tolerant networking. In 3GPP context, a service that could be assimilated to an S&F service is SMS, for which there is no need to have an end-to-end connectivity between the end-points (e.g., an end-point can be the UE (102) 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 NGSO satellites.

[0090] Fig. 5 is a block diagram that illustrates a high-level overview of communication between the satellite (402) and the UE (102) according to the prior art. Fig. 5 illustrates consolidated requirements for UE-satellite-UE communication. Here, the satellite (402) is in communication with multiple UEs (UE1, UE2, etc.) and a remote data network (DN) (502).

[0091] Fig. 6 is a block diagram that illustrates a high-level overview of satellite architecture according to the prior art. As shown, the satellite (402) includes an Evolved Node-B (eNB) (602) and an MME on-board (604) or any other network entity to support S&F registration / attach procedure and an MME-ground (606) on the ground. The network function (NF) may be with complete capability or some lighter version of the NF with capabilities required to handle the registration procedure on-board.

[0092] Embodiments disclosed herein provide a system and method for wait range / timer handling for satellite communication. The current approach involves the UE (102) that listens for and responds to notifications with the option to halt the wait timer if it is active during the registration process or any other NAS signaling in satellite communication. The proposed method offers solutions for managing wait range timer information and configuration during the registration process or any other NAS signaling within satellite communication.

[0093] In an embodiment, a list of NAS messages includes, but is 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, registration accept, deregistration accept, service reject, service accept, UE configuration update command, UE parameters update command, 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, and detach reject message.

[0094] In an embodiment the term EMM sublayer states are at least one of the below:

[0095] 1) EMM-NULL

[0096] 2) EMM-DEREGISTERED

[0097] a) EMM-DEREGISTERED.NORMAL-SERVICE

[0098] b) EMM-DEREGISTERED.LIMITED-SERVICE

[0099] c) EMM-DEREGISTERED.ATTEMPTING-TO-ATTACH

[0100] d) EMM-DEREGISTERED.PLMN-SEARCH

[0101] e) EMM-DEREGISTERED.NO-IMSI

[0102] f) EMM-DEREGISTERED.ATTACH-NEEDED

[0103] g) EMM-DEREGISTERED.NO-CELL-AVAILABLE

[0104] h) EMM-DEREGISTERED.eCALL-INACTIVE

[0105] 3) EMM-REGISTERED-INITIATED

[0106] 4) EMM-REGISTERED

[0107] a) EMM-REGISTERED.NORMAL-SERVICE

[0108] b) EMM-REGISTERED.ATTEMPTING-TO-UPDATE

[0109] c) EMM-REGISTERED.LIMITED-SERVICE

[0110] d) EMM-REGISTERED.PLMN-SEARCH

[0111] e) EMM-REGISTERED.UPDATE-NEEDED

[0112] f) EMM-REGISTERED.NO-CELL-AVAILABLE

[0113] g) EMM-REGISTERED.ATTEMPTING-TO-UPDATE-MM

[0114] h) EMM-REGISTERED.IMSI-DETACH-INITIATED

[0115] 5) EMM-DEREGISTERED-INITIATED

[0116] 6) EMM-TRACKING-AREA-UPDATING-INITIATED

[0117] 7) EMM-SERVICE-REQUEST-INITIATED

[0118] The term 5GMM sublayer state in this embodiment is at least one of the below:

[0119] 1) 5GMM-NULL

[0120] 2) 5GMM-DEREGISTERED

[0121] a) 5GMM-DEREGISTERED.NORMAL-SERVICE

[0122] b) 5GMM-DEREGISTERED.LIMITED-SERVICE

[0123] c)5GMM-DEREGISTERED.ATTEMPTING-REGISTRATION

[0124] d) 5GMM-DEREGISTERED.PLMN-SEARCH

[0125] e) 5GMM-DEREGISTERED.NO-SUPI

[0126] f) 5GMM-DEREGISTERED.NO-CELL-AVAILABLE

[0127] g) 5GMM-DEREGISTERED.eCALL-INACTIVE

[0128] h)5GMM-DEREGISTERED.INITIAL-REGISTRATION-NEEDED

[0129] 3) 5GMM-REGISTERED-INITIATED

[0130] 4) 5GMM-REGISTERED

[0131] a) 5GMM-REGISTERED.NORMAL-SERVICE

[0132] b) 5GMM-REGISTERED.NON-ALLOWED-SERVICE

[0133] c)5GMM-REGISTERED.ATTEMPTING-REGISTRATION-UPDATE

[0134] d) 5GMM-REGISTERED.LIMITED-SERVICE

[0135] e) 5GMM-REGISTERED.PLMN-SEARCH

[0136] f) 5GMM-REGISTERED.NO-CELL-AVAILABLE

[0137] g) 5GMM-REGISTERED.UPDATE-NEEDED

[0138] 5) 5GMM-DEREGISTERED-INITIATED

[0139] 6) 5GMM-SERVICE-REQUEST-INITIATED

[0140] In an embodiment, the term RAT is defined to encompass a variety of technologies. These include Next Generation Radio Access Network (NG-RAN), 5G, 4G, 3G, and 2G. Additionally, Evolved Packet System (EPS) and 5GS are included within this definition. The term also covers NR, NR in unlicensed bands, and various satellite access technologies such as NR Low Earth Orbit (LEO), NR Medium Earth Orbit (MEO), NR Geostationary Orbit (GEO), and NR (OTHER Satellite (SAT)). Furthermore, NR RedCap and Evolved Universal Mobile Telecommunication Access (E-UTRA) are part of this definition, as well as E-UTRA in unlicensed bands. The definition extends to NB-IoT, WB-IoT, and LTE-M.

[0141] In an embodiment, the 5GS registration type includes initial registration, mobility registration updating, periodic registration updating, emergency registration, Standalone Non-Public Networks (SNPN) onboarding registration, disaster roaming initial registration, or disaster roaming mobility registration updating.

[0142] Satellite: an artificial body placed in orbit around the earth, moon, or another planet in order to collect information or for communication.

[0143] Satellite Constellation: Group of satellites placed in orbit around the earth, moon, or another planet in order to collect information or for communication.

[0144] 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.

[0145] Continuous Coverage: In Non-Terrestrial Networks (NTN), continuous satellite coverage can be characterized by the fact that an Uu interface (radio interface between the UE and the Node B) is available for the UE (102) at a given position for 100% of the time.

[0146] DC: In the NTN, discontinuous satellite coverage can be characterized by the fact that the Uu interface is available for the UE (102) at a given position less than 100% of the time due to a predictable lack of satellite coverage. Due to the DC, the UE (102) may have access to satellite service coverage only at specific times and places.

[0147] Satellite Ephemeris Information: Global Positioning System (GPS) satellites transmit information about their location (current and predicted), timing, and "health" via what is known as ephemeris data. This data is used by the GPS receivers to estimate location relative to the satellites and thus position on earth.

[0148] 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.

[0149] The Ephemeris Data can also be used to predict future satellite conditions (for a given place and time), providing a tool for planning when (or when not) to schedule GPS data collection.

[0150] PLMN selection as per 23.122 without RPLMN:

[0151] The Mobile Station (MS) selects and attempts registration on any PLMN / access technology combinations if available and allowable in the following order:

[0152] either Home PLMN (HPLMN) (if the Equivalent Home Public Land Mobile Network (EHPLMN) list is not present or is empty) or the highest priority EHPLMN that is available (if the EHPLMN list is present),

[0153] each PLMN / access technology combination in the "User Controlled PLMN Selector with Access Technology" data file in the SIM (in priority order),

[0154] 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 a Mobile Equipment (ME) (in priority order),

[0155] other PLMN / access technology combinations with received high-quality signal in random order,

[0156] other PLMN / access technology combinations in order of decreasing signal quality.

[0157] PLMN selection as per 23.122 with RPLMN:

[0158] The MS selects and attempts registration on any PLMN / access technology combinations if available and allowable in the following order: either the RPLMN or the last registered PLMN; 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); each PLMN / access technology combination in the "User Controlled PLMN Selector with Access Technology" data file in the SIM (in priority order); 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); other PLMN / access technology combinations with received high-quality signal in random order; other PLMN / access technology combinations in order of decreasing signal quality. For the 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 two different operators having an agreement. The NTN and TN could either operate in two different frequency bands (e.g., FR1 vs. FR2) or in the same frequency band (e.g., FR1 or FR2). 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. 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 are 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 (Narrow Band Internet of Things) or WB-IOT (Wide Band Internet of Things) Satellite Access / Architecture. The solutions which are defined for 5G Core (5GC) are also applicable to legacy RATs like E-UTRA / LTE; the corresponding CN entities need to be replaced by LTE entities, e.g., AMF with MME, g-nodeB with e-nodeB, Unified data management (UDM) with HSS, etc. But principles of the solution remain the same.

[0159] 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. The network apparatus (202) used in this embodiment is explained using any 5G Core Network Function, e.g., AMF. However, the network apparatus (202) could be any 5G / Evolved Universal Mobile Telecommunication Access Network (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 signalling messages between the UE (102) and the network apparatus (202) or between different Network functions / entities. The term area / location / geographical area used in this embodiment may refer to any of cell / cell identity (ID), Tracking Area Code (TAC) / Tracking Area Identity (TAI), PLMN, Mobile Country Code (MCC) / Mobile Network Code (MNC), Latitude / longitude, Closed Access Group (CAG) cell, or any geographical location / coordinate.

[0160] The issues or solutions disclosed in this embodiment are explained using 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 WB (Wide Band)-S1 mode via E-UTRAN access and / or NB-IOT (Narrow Band Internet Of Things) or WB-IOT (Wide Band Internet Of Things) 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, e.g., AMF with MME, g-nodeB with e-nodeB, UDM with HSS, etc. But principles of the solution remain the same. The network apparatus (202) used in this embodiment is explained using any 5G Core Network Function, e.g., 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 signalling messages between the UE (102) and the network apparatus (202) or between different Network functions / entities. The terms camp and register are used interchangeably and have the same meaning. The terms wait timer, DC wait timer, DC wait timer, Random timer, Random wait timer, DCW Timer, Maximum Time Offset, DC maximum time offset are all used interchangeably and have the same meaning. The terms wait range, DC wait range, DC Range, DCW Range, Discontinuous wait range, DC wait range are all used interchangeably and have the same meaning.

[0161] The term area as used in this embodiment may refer to any of cell / cell ID, Tracking Area Code (TAC) / Tracking Area Identity (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 Access Stratum (AS) messages, please refer to 3GPP TS 38331 or 3GPP TS 36331. The cause names in this embodiment are for illustration purposes, and they can have any name. The NAS messages and 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 the UE (102) and AMF / MME or UE and gNB (NG-RAN / any RAN node) / eNB.

[0162] In order to reduce the impact due to a large number of UEs triggering signaling load on the network returning after DC, the network apparatus (202) determines the "wait range" based on network configuration and sends the "DC wait range" to the UE (102) via the Registration procedure or UE Configuration Update procedure. If the UE (102) has decided to remain in no service (e.g., by applying power saving) due to the DC and wait until the same RAT / PLMN coverage to return, the UE (102) will calculate the "wait timer" based on "DC wait range" configuration from the network (e.g., by selecting a random value between 0 and "DC wait range") and starts the respective "wait timer" when returning to coverage after being in the DC to reduce signaling overload on the same RAT / PLMN. The UE (102) will not initiate any NAS signaling when the "wait timer" is running.

[0163] Embodiments disclosed herein provide a system and method for the satellite (402) to handle the attach request / registration request received from the UE (102) when the satellite (402) does not have UE information / UE context / UE subscription details. The present method includes the satellite (402) handling the attach request / registration request received from the UE (102) when the satellite (402) does not have UE information / UE context / UE subscription details. Further, the method includes handling a round trip time between the UE (102) and the MME-ground (606) on the ground when the UE (102) is in a location where there is no terrestrial network and the satellite (402) serving the UE (102) has no feeder link available.

[0164] VisitedPLMN (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).

[0165] 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 General Packet Radio Service (GPRS) service" in the MS.

[0166] Available PLMN:PLMN(s) in the given area which is / are broadcasting capability to provide wireless communication services to the UE (102).

[0167] 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.

[0168] EHPLMN:Any of the PLMN entries contained in the Equivalent HPLMN list.

[0169] 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 a Universal Subscriber Identity Module (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.

[0170] Home PLMN:This is a PLMN where the MCC and MNC of the PLMN identity match the MCC and MNC of the IMSI.

[0171] 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.

[0172] Registration:This is the process of camping on a cell of the PLMN or the SNPN and doing any necessary LRs.

[0173] UPLMN:PLMN / access technology combination in the "User Controlled PLMN Selector with Access Technology" data file in the SIM (in priority order).

[0174] 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).

[0175] Feeder Link:Feeder link can be defined as　a wireless link between the NTN Gateway and the satellite (402).

[0176] Service Link:Service link is the radio link between the UE (102) and the satellite (402).

[0177] Referring now to the drawings, and more particularly to Figs. 7 through 13 where similar reference characters denote corresponding features consistently throughout the figures, there are shown preferred embodiments.

[0178] Fig. 7 is a block diagram of the UE (102) handling after a DC period has ended during satellite communication according to an embodiment as disclosed herein. The UE (102) may include, but is not limited to, a smartphone, a laptop, a tablet, a personal computer (PC), an Internet of Things device, and the like. As shown, the UE (102) includes a processor (104), a memory (106), an I / O interface (108), and a first controller (110) communicatively coupled to the processor (104) and the memory (106). Each component is explained in further detail below.

[0179] The processor (104) communicates with the memory (106), the I / O interface (108), and the first controller (110). The processor (104) is configured to execute instructions stored in the memory (106) and to perform various processes. The processor (104) 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).

[0180] The memory (106) includes storage locations to be addressable through the processor (104). The memory (106) is not limited to a volatile memory and / or a non-volatile memory. Further, the memory (106) may include a plurality of computer-readable storage media. The memory (106) 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.

[0181] The I / O interface (108) transmits the information between the memory (106) and external peripheral devices. The peripheral devices are the input-output devices associated with the first controller (110). Further, the first controller (110) communicates with the I / O interface (108) and the memory (106). The first controller (110) may be communicatively coupled to the memory (106) and the processor (104). The first controller (110) 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.

[0182] In an embodiment, the first controller (110) starts a DC maximum time offset timer in response to determining that a DC period has ended during satellite communication. The DC maximum time offset timer ensures that the offset (or delay) between expected and actual times of communication or scheduling events does not exceed a specified maximum. The DC period refers to scenarios where signal coverage is intermittent or non-continuous, possibly due to mobility or environmental factors (e.g., buildings, tunnels) associated with the UE (102). For instance, the UE (102) starts the DC maximum time offset timer upon returning in a satellite coverage of a tracking area (TA) in a current registration area after being out of satellite coverage due to the DC, and the UE (102) has stored a DC maximum time offset. The satellite coverage of the TA in the current registration area refers to the geographical region covered by a satellite's communication capabilities, specifically within the boundaries of the TA that is part of a registration area in communication networks.

[0183] In an embodiment, the first controller (110) receives a notification message from the network apparatus (202) over the non-3GPP access (302). These networks provide alternative ways for the UE (102) to connect to the core network. The notification message includes an access type indicator set to 3GPP access. Further, the notification message indicates pending downlink data or downlink signaling over 3GPP access from the network apparatus (202) to the UE (102). The access type indicator set to 3GPP access is a parameter used in communication systems to identify the type of network access technology that the UE (102) is using to connect to the core network. When the indicator is set to 3GPP access, it signifies that the connection is made through a 3GPP-standardized radio access technology. Further, the pending downlink data or downlink signaling refers to information or control messages that are queued or waiting to be delivered from the network apparatus (202) to the UE (102).

[0184] The UE (102) is in the 5GMM-IDLE mode over 3GPP access and in 5GMM-CONNECTED mode over the non-3GPP access (302). In the 5GMM-IDLE mode, the UE (102) is not actively connected to the 5G Core (5GC) for data transfer but remains registered with the network apparatus (202). The UE (102) uses periodic updates (Tracking Area Updates, TAU) to inform the network apparatus (202) about its location. When in 5GMM-IDLE mode over 3GPP access, the UE (102) is registered with the network apparatus (202) via 3GPP-defined access technologies but is in a low-power idle state. In the 5GMM-CONNECTED mode, the UE (102) has an active connection with the network apparatus (202) and can send and receive data in real-time. Mobility is managed through handovers instead of periodic updates, ensuring a seamless experience.

[0185] In an embodiment, the first controller (110) determines whether the DC maximum time offset timer associated with the UE (102) is running upon receiving the notification message. The first controller (110) then stops the DC maximum time offset timer when it is determined to be running.

[0186] In an embodiment, the first controller (110) initiates a NAS signalling procedure over 3GPP access for reception of the pending downlink data or downlink signalling from the network apparatus (202). The NAS signalling procedure refers to the exchange of signalling messages between the UE (102) and the network apparatus (202) for managing mobility, session establishment, and security. NAS procedures occur over a control plane and are independent of the specific radio access technology (RAT) used. The NAS signalling ensures the UE (102) remains connected to the network apparatus (202) while moving across different cells or access types. The NAS procedure is initiated only when the DC maximum time offset timer is stopped. The UE (102) does not initiate any NAS signalling on an NR satellite access and a public land mobile network (PLMN) while the DC maximum time offset timer is running.

[0187] Fig. 8 is a block diagram of the network apparatus (202) handling after a DC period has ended during satellite communication according to an embodiment as disclosed herein. For instance, the network apparatus (202) may include an AMF or any other network entities. For example, the network entities may include SMF, MME, UPF, 5G / EUTRAN RAN entities (eNodeB (eNB) or gNodeB (gNB), NG-RAN, and the like).

[0188] As shown, the network apparatus (202) includes a second processor (204), a second memory (206), a second I / O interface (208), and a second controller (210) communicatively coupled to the second processor (204) and the second memory (206). The second controller (210) communicates with the second I / O interface (208) and the second memory (206). The second controller (210) may be communicatively coupled to the second memory (206) and the second processor (204). The second controller (210) 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.

[0189] In an embodiment, the second controller (210) determines to deliver data to the UE (102) during the DC period. The term "DC period" refers to scenarios where the availability of signal coverage is not uniform or stable, leading to interruptions in connectivity. This can occur due to a variety of factors, including the movement of the UE (102) and the surrounding environment.

[0190] In an embodiment, the second controller (210) transmits a notification message to the UE (102) over the non-3GPP access (302). The notification message serves as an important communication signal indicating that there is pending downlink data or signalling that needs to be transmitted from the network apparatus (202) to the UE (102). This downlink data may include various types of information, such as user data, control messages, or updates that are essential for maintaining the connection and ensuring optimal performance of the user equipment. Further, the notification message includes an access type indicator. This indicator is specifically configured to align with the standards set forth by the 3GPP, which is responsible for developing protocols for telecommunications.

[0191] In an embodiment, the second controller (210) detects initiation of the NAS signaling procedure from the UE (102) after sending the notification message. This procedure is essential for establishing or maintaining a connection and ensuring that the UE (102) can effectively communicate with the network apparatus (202). The second controller (210) then transmits the pending downlink data or downlink signaling to the UE (102) after initiation of the NAS signaling procedure. This downlink data may include important information such as updates, configuration parameters, or other necessary signaling that the UE (102) requires to continue its operation within the network apparatus (202).

[0192] Fig. 9 is a sequence diagram that illustrates a scenario of the UE (102) responding to notification and optionally stop the wait timer it is running according to an embodiment as disclosed herein. As shown in the sequence diagram, the UE (102) is in communication with the network apparatus (202) via the non-3GPP access (302). At step 1, the network apparatus (202) determines the "wait range" based on network configuration and sends the "DC wait range" to the UE (102) by the Registration procedure or UE Configuration Update procedure or any other signalling.

[0193] At step 2, the UE (102) enters DC and it starts to search for coverage again when it exits DC (timer). The UE (102) starts random wait timer (also called as wait timer or DC maximum time offset timer it can be any name in this embodiment) based on DC wait range on finding coverage again.

[0194] At step 3, the network apparatus (202) has DL data / DL signalling for the UE (102) at this time when the random wait timer is running at the UE (102). At step 4, the network apparatus (202) sends the notification message over the Non-3GPP access (302) (e.g.N3IWF) to the UE (102) for the pending DL data / DL signalling. At step 5, during the wait timer duration, on receiving NOTIFICATION message over the non-3GPP access (302) optionally indicating 3GPP access type, the UE (102) will stop the wait timer i.e. DC maximum time offset timer (if running) and get into RRC-CONNECTED mode immediately by triggering NAS procedure like service request procedure etc over 3GPP access. The UE (102) is at least in one of the 5GMM sublayer states or EMM sublayer states.

[0195] When the random wait timer is running in the UE (102), if higher layers trigger PLMN search, i.e. if search is triggered(for e.g. due to timer T expiry) for any other PLMN or RAT, the UE (102) should stop the wait timer and camp to the found PLMN

[0196] In an embodiment, the UE (102) will stop the wait timer if the UE (102) selects other PLMN / RAT than the PLMN which configured wait range in the UE (102). The UE (102) will stop the wait timer if the UE (102) selects the second PLMN / RAT, but the UE (102) is configured with / by wait range configuration by first PLMN (to apply for first PLMN).

[0197] In an embodiment, the UE (102) will stop the wait timer if it receives registration / TAU accept from the network apparatus (202) (optionally except for emergency registration or emergency attach).

[0198] In an embodiment, the UE (102) may keep running the wait timer for the first PLMN / RAT for which the wait timer was configured, but it can search and camp on second PLMNs / RATs for which the wait timer is not configured. The UE (102) may move back / reselect to the first PLMN for which wait timer was configured only after such timer expires the UE (102) is allowed to access (trigger NAS signalling) on first PLMN / RAT.

[0199] In an embodiment, if the wait timer is running and the UE (102) has emergency services (e.g. Packet Data Unit (PDU) session for emergency service or emergency call) has to be performed, the UE (102) should stop the wait timer in such cases and immediately trigger service request / registration for emergency services.

[0200] Alternatively, the UE (102) may continue to run the wait timer, but it is allowed to perform emergency attach / registration or emergency PDU sessions when the wait timer is running.

[0201] In an embodiment, the UE (102) shall stop the DC maximum time offset timer and initiate NAS signalling if the UE (102) receives paging message, has pending emergency services, is establishing an emergency PDU session or is performing emergency services fallback procedure, powers off, receives a NOTIFICATION message over the non-3GPP access (302) or when the UE (102) enters a TAI outside the registration area. At expiry of the DC maximum time offset timer the UE (102) shall perform a registration procedure for mobility registration update.

[0202] When after exiting the DC, the UE (102) finds coverage in any other PLMN / RAT for which the wait timer was NOT configured, it can get into RRC-CONNECTED state irrespective of the wait timer. The wait timer will be stopped by the UE (102). The UE (102) may stop the wait timer in such scenario, or it may keep running the timer and will not move to the PLMN / RAT for which the wait timer was configured till the timer is expired. After the expiry of wait timer, it may trigger PLMN search / selection to reselect to the PLMN for which wait timer was configured.

[0203] Fig. 10 is a sequence diagram that illustrates a scenario of the UE (102) behaviour regarding disco wait range and wait timer according to an embodiment as disclosed herein. As shown in the sequence diagram, the UE (102) is in communication with the network apparatus (202). At step 1, the network apparatus (202) provides the DisCo Wait Range to the UE (102) (via Registration procedure or UE Configuration Update procedure or any NAS / AS signalling)

[0204] At step 2, the UE (102) calculates the "wait timer" based on "Disco Wait Range" configuration from the network (e.g. by selecting a random value between 0 and "Disco Wait Range"). Optionally, the UE (102) stores / saves the Disco Wait Range and / or wait timer information / configuration in the UE (102) (ME or USIM or eSIM). At step 3, the DC is detected in the current geographic area and the UE (102) enters the DC. At step 4, when the UE (102) detects the DC ends, the UE (102) starts the wait timer. At step 5, the UE (102) or the upper layers performs any of the following:

[0205] Switch-Off / powers off and optionally Switch-ON i.e. the UE (102) has changed 5GMM sublayer states from 5GMM-REGISTERED to 5GMM-DEREGISTERED or from 5GMM-DEREGISTERED to 5GMM-REGISTERED or there is any change in the UE's states in any of the 5GMM sublayer states or EMM sublayer states.

[0206] ▷ SIM / USIM Removal and optionally same / new SIM / USIM insertion

[0207] ▷ SIM / USIM / eSIM has changed i.e. new SIM / USIM / eSIM is inserted / provisioned.

[0208] ▷ The UE (102) selects / registers on / camps on alternate RAT / PLMN / Access / Network

[0209] ▷ SUPI in SIM / USIM / eSIM has changed

[0210] At step 6, when the UE (102) detects any of the above procedures or events, the UE (102) deletes / stops the wait timer, if stored / configured / provisioned and already running, and / or the UE (102) doesn't start the wait timer, if stored / configured / provisioned and not started yet.

[0211] In an embodiment, the UE (102) shall delete (or optionally set the value to 0 or any value to indicate that the DisCo Wait Range / Timer is not configured) any information or configuration for the DisCo Wait Range and / or the wait timer if stored / configured / provisioned in the UE (102) (ME / USIM / eSIM).

[0212] In an embodiment, the UE (102) shall delete (or optionally set the value to 0 or any value to indicate that the DisCo Wait Range / Timer is not configured) any information or configuration for the DisCo Wait Range and / or the wait timer if stored / configured / provisioned in the UE (102) (ME / USIM / eSIM) only for the registered / last registered Network / RAT / PLMN / Access.

[0213] In an embodiment, the UE (102) shall delete (or optionally set the value to 0 or any value to indicate that the DisCo Wait Range / Timer is not configured) any information or configuration for the DisCo Wait Range and / or the wait timer if stored / configured / provisioned in the UE (102) (ME / USIM / eSIM) for all the Network / RAT / PLMN / Access.

[0214] In an embodiment, the DC maximum time offset value can only be used if the SUPI from the USIM matches the SUPI stored in the non-volatile memory of the ME; else the UE (102) shall delete the DC maximum time offset value.

[0215] The UE (102) shall perform any of the below steps in any order or combinations:

[0216] When the DisCo Wait Range and / or the wait timer is stored / configured / provisioned in the UE (102) (ME / USIM / eSIM) and the UE (102) receives REGISTRATION ACCEPT / UE Configuration Update (UCU) Command or message or any AS / NAS signalling message from the network apparatus (202) without Disco Wait Range and / or wait timer information or with any indication / IE from the network apparatus (202) stating that Disco Wait Range and / or wait timer information is not configured / provisioned or the network apparatus (202) sends an empty or value set to 0 for the Disco Wait Range and / or wait timer information, then the UE (102) shall delete (or optionally set the value to 0 or any value to indicate that the DisCo Wait Range / Timer is not configured) any information or configuration for the DisCo Wait Range and / or the wait timer if stored / configured / provisioned in the UE (102) (ME / USIM / eSIM).

[0217] In an embodiment, the UE (102) shall delete (or optionally set the value to 0 or any value to indicate that the DisCo Wait Range / Timer is not configured) any information or configuration for the DisCo Wait Range and / or the wait timer if stored / configured / provisioned in the UE (102) (ME / USIM / eSIM) only for the registered / last registered Network / RAT / PLMN / Access.

[0218] In an embodiment, the UE (102) shall delete (or optionally set the value to 0 or any value to indicate that the DisCo Wait Range / Timer is not configured) any information or configuration for the DisCo Wait Range and / or the wait timer if stored / configured / provisioned in the UE (102) (ME / USIM / eSIM) for all the Network / RAT / PLMN / Access.

[0219] When the DisCo Wait Range and / or the wait timer is stored / configured / provisioned in the UE (102) (ME / USIM / eSIM) and the UE (102) or the upper layers perform Switch-Off and optionally Switch-ON or if there is any change in the 5GMM sublayer states or the EMM sublayer states of the UE (102) (for e.g. the 5GMM sublayer states of the UE (102) has changed from 5GMM-REGISTERED to 5GMM-DEREGISTERED or from 5GMM-DEREGISTERED to 5GMM-REGISTERED), then the UE (102) shall delete (or optionally set the value to 0 or any value to indicate that the DisCo Wait Range / Timer is not configured) any information or configuration for the DisCo Wait Range and / or the wait timer if stored / configured / provisioned in the UE (ME / USIM / eSIM).

[0220] In an embodiment, the UE (102) shall delete (or optionally set the value to 0 or any value to indicate that the DisCo Wait Range / Timer is not configured) any information or configuration for the DisCo Wait Range and / or the wait timer if stored / configured / provisioned in the UE (102) (ME / USIM / eSIM) only for the registered / last registered Network / RAT / PLMN / Access.

[0221] In an embodiment, the UE (102) shall delete (or optionally set the value to 0 or any value to indicate that the DisCo Wait Range / Timer is not configured) any information or configuration for the DisCo Wait Range and / or the wait timer if stored / configured / provisioned in the UE (102) (ME / USIM / eSIM) for all the Network / RAT / PLMN / Access.

[0222] When the DisCo Wait Range and / or the wait timer is stored / configured / provisioned in the UE (102) (ME / USIM / eSIM) and the UE's SIM / USIM / eSIM has changed or there is any change in the SIM / USIM / eSIM configuration (for e.g. new SIM / USIM / eSIM is inserted / provisioned) or if the SIM / USIM is removed and / or optionally inserted / re-inserted, then the UE (102) shall delete (or optionally set the value to 0 or any value to indicate that the DisCo Wait Range / Timer is not configured) any information or configuration for the DisCo Wait Range and / or the wait timer if stored / configured / provisioned in the UE (102) (ME / USIM / eSIM).

[0223] In an embodiment, the UE (102) shall delete (or optionally set the value to 0 or any value to indicate that the DisCo Wait Range / Timer is not configured) any information or configuration for the DisCo Wait Range and / or the wait timer if stored / configured / provisioned in the UE (102) (ME / USIM / eSIM) only for the registered / last registered Network / RAT / PLMN / Access.

[0224] In an embodiment, the UE (102) shall delete (or optionally set the value to 0 or any value to indicate that the DisCo Wait Range / Timer is not configured) any information or configuration for the DisCo Wait Range and / or the wait timer if stored / configured / provisioned in the UE (102) (ME / USIM / eSIM) for all the Network / RAT / PLMN / Access.

[0225] When the DisCo Wait Range and / or the wait timer is stored / configured / provisioned in the UE (102) (ME / USIM / eSIM) and the UE (102) selects / registers on / camps on / performs PLMN search and selects alternate RAT or PLMN or Access or Network, then the UE (102) shall delete (or optionally set the value to 0 or any value to indicate that the DisCo Wait Range / Timer is not configured) any information or configuration for the DisCo Wait Range and / or the wait timer if stored / configured / provisioned in the UE (102) (ME / USIM / eSIM). Alternatively the UE shall delete the DisCo Wait Range and / or the wait timer when the UE moves out of the registration area or TAI list i.e. the UE considers the DisCo Wait Range and / or the wait timer only in the registration area where it received it and outside it is deactivated or deleted.

[0226] If DisCo Wait Range(also called as Minimum offset value) IE is received with value 000 or is not received in the TAU accept / registration accept or attach accept message, the UE should delete the DisCo Wait Range and stop the wait timer(if running).

[0227] In an embodiment, the UE (102) shall delete (or optionally set the value to 0 or any value to indicate that the DisCo Wait Range / Timer is not configured) any information or configuration for the DisCo Wait Range and / or the wait timer if stored / configured / provisioned in the UE (102) (ME / USIM / eSIM) only for the registered / last registered Network / RAT / PLMN / Access.

[0228] In an embodiment, the UE (102) shall delete (or optionally set the value to 0 or any value to indicate that the DisCo Wait Range / Timer is not configured) any information or configuration for the DisCo Wait Range and / or the wait timer if stored / configured / provisioned in the UE (102) (ME / USIM / eSIM) for all the Network / RAT / PLMN / Access.

[0229] Optionally, the last registered PLMN in this embodiment is an illustration for the PLMN which has configured the DC wait range / wait timer.

[0230] When the UE (102) is switched off when the wait timer is running, the UE (102) shall behave as follows when the UE (102) is switched on and the USIM in the UE (102) remains the same: Let t1 be the time remaining for wait timer to timeout at switch off and let t be the time elapsed between switch off and switch on. If t1 is greater than t, then the timer shall be restarted with the value t1　-　t. If t1 is equal to or less than t, then the timer need not be restarted and considered expired. If the UE (102) is not capable of determining t, then the UE (102) shall restart the timer with the value t1.

[0231] Fig. 11 is a sequence diagram that illustrates attach without a PDN connectivity for a single satellite according to an embodiment as disclosed herein. As shown in the sequence diagram, the UE (102), the satellite (402) (including the eNB (602) and MME on-board (604), and the HSS (1102) are in communication with each. Each step is explained in further detail below.

[0232] The eNB (602) and the MME on-board (604) are assumed to be onboard the satellite, rest of the system is on the ground. The attach procedure as described in 3GPP TS 23.401 clause .5.3.2.1 are executed with below modifications:

[0233] At time T0 (i.e. when 5G system on board satellite is serving the UE (102), and feeder link connectivity is not available):

[0234] In step 1, when the UE (102) identifies that current serving cell support S&F mode and the UE (102) is allowed to use S&F, then the UE (102) sends Attach Request message to network.

[0235] Steps up to step 4 are executed between the MME on-board (604) and the UE (102). The MME on-board (604) sends NAS message Partial attach accept (which can be unprotected) to the UE (102), indicating to the UE (102) that the sent ATTACH REQUEST message is stored by the MME on-board (604) and the network will reach the UE (102) once the UE authentication and subscription details are fetched by the MME on-board (604) from the ground network (404). The Partial attach accept includes a temporary GUTI or any identifier(though the UE (102) is not registered with network). The MME on-board (604) memorizes the UE serving area. The UE (102) shall not trigger attach request again until paging message is received or it comes in and out of the DC period.

[0236] In an embodiment, alternative way is paging with IMSI. The UE (102) receives a partial attach accept message which is unprotected. The UE (102) shall not trigger attach request again until paging message is received or it comes in and out of the DC period.

[0237] In an embodiment, the UE (102) can assume partial attach accept if the message is not security protected.

[0238] At time T1 (i.e. when 5G system on board the satellite (402) is connected to ground network (404) but cannot connect to the UE (102), and feeder link connectivity is available):

[0239] Step 5 is executed between the MME on-board (604) and the HSS (1102), i.e. the MME on-board (604) fetches the authentication vector and other subscription details from the HSS (1102) etc.

[0240] Steps 8 & 11 are executed when Update location with the HSS (1102) and Update location ACK is received by the MME on-board (604). I.e. all the subscription details are retrieved by the MME on-board (604). The MME on-board (604) indicates S&F to the HSS (1102) to retrieve subscription details specific to S&F (if any) and indicates that it is pre-fetching the subscription data without authenticating the UE (102).

[0241] At time T2 (i.e. when 5G system on board the satellite (402) start serving the UE (102) again, and feeder link connectivity is not available):

[0242] The MME on-board (604) when enters the UE (102) serving area will page the UE (102) with the assigned GUTI or temporary identifier in Partial attach accept message. The UE (102) in response to receiving the paging message or on detecting the signal from same operator is available (i.e. DC period has ended), the UE (102) re-sends the Attach request message. The MME on-board (604) executes the step 5 of authentication and security procedure with the UE (102), once authentication procedure is successful then system executes remaining steps to complete Attach procedure with the UE (102). The MME on-board (604) also provide S&F policies to the UE (102). The MME on-board (604) based on subscription data available may send the reject message to the UE (102) before or after the authentication / security procedure are executed.

[0243] At time T3, the MME on-board (604) sends Update location indicating to the HSS (1102) that the UE (102) is authenticated successfully or not authenticated successfully.

[0244] In an embodiment, when security needs to be executed the step-1 described in this embodiment is described.

[0245] At time T0 (i.e. when 5G system on board satellite is serving the UE (102), and feeder link connectivity is not available):

[0246] In step 1, if the UE (102) identifies that the current serving cell supports S&F mode and the UE (102) is allowed to use S&F, then the UE (102) sends an Attach Request message to the network. Steps up to step 4 are executed between the MME on-board (604) and the UE (102). The MME on-board (604) sends a NAS message, Partial Attach Accept (which is unprotected), to the UE (102), indicating to the UE (102) that the sent ATTACH REQUEST message is stored by the MME on-board (604) and the network will reach the UE (102) once the UE authentication and subscription details are fetched by the MME on-board (604) from the ground network (404). The Partial Attach Accept includes a temporary GUTI (though the UE (102) is not registered with the network). The MME on-board (604) memorizes the UE serving area.

[0247] The UE (102) receives the Partial Attach Accept message, which is unprotected. The UE (102) shall not trigger the attach request again until a paging message is received. At time T1 (i.e., when the 5G system on board the satellite (402) is connected to the ground network (404) but cannot connect to the UE (102) and feeder link connectivity is available), the MME on-board (604) forwards the stored attach request message and the UE (102) serving area to the MME-ground (606). Step 5 is executed between the MME-ground (606) and the HSS (1102), i.e., the MME-ground (606) fetches the authentication vector and other details from the HSS (1102), etc.

[0248] Step 8 & 11 are executed, i.e., the update location with the HSS (1102) and the update location ACK is received by the MME-ground (606). i.e., all the subscription details are retrieved by the MME-ground (606). The MME-ground (606) indicates S&F to the HSS (1102) to retrieve subscription details specific to S&F (if any) and indicates that it is pre-fetching the subscription data without authenticating the UE (102).

[0249] The MME-ground (606) syncs with the UE (102) information it retrieved with the MME on-board (604). For optimization purposes, the MME on-board (604) can be any onboard MME which will serve the UE (102) next.

[0250] At time T2 (i.e., when the 5G system on board the satellite (402) starts serving the UE (102) again and the feeder link connectivity is not available).

[0251] The MME on-board (604), when it enters the UE serving area, will page the UE (102) with the assigned GUTI in the partial attach accept message. The UE (102), in response to receiving the paging message, re-sends the attach request message.

[0252] The MME on-board (604) executes step 5 of the authentication and security procedure with the UE (102). Once the authentication procedure is successful, the system executes the remaining steps to complete the attach procedure with the UE (102). The MME-ground (606), based on subscription data available, may send the reject message to the UE (102) before or after the authentication / security procedures are executed.

[0253] Fig. 12 is a flow diagram that illustrates a method for handling downlink data or downlink signaling during a satellite communication from the UE (102) according to an embodiment as disclosed herein. The method includes steps (1202-1310). Each step is explained in further detail below.

[0254] At step (1202), the UE (102) starts a DC maximum time offset timer in response to determining that a DC period has ended during satellite communication. The maximum time offset timer for the DC is designed to ensure that the delay between the anticipated and actual times of communication or scheduling events remains within a predetermined limit. The DC pertains to situations where signal availability is sporadic or inconsistent, often influenced by mobility or environmental conditions such as buildings or tunnels affecting the user equipment (UE) (102). For example, the UE (102) activates the maximum time offset timer for the DC when it re-enters a satellite coverage area of a tracking area (TA) within its current registration area, after having been outside of satellite coverage due to intermittent connectivity. The satellite coverage of the TA in the current registration area denotes the geographical zone where a satellite can provide communication services, specifically within the confines of the TA that is part of a broader registration area in communication networks.

[0255] At step (1204), the UE (102) receives a notification message from the network apparatus (202) over the non-3GPP access (302). Non-3GPP access (302) pertains to communication technologies and networks that fall outside the scope of 3GPP standards. These networks offer alternative methods for the UE (102) to establish a connection with the core network. The notification message contains an access type indicator that is designated as 3GPP access. Additionally, this message signifies that there is pending downlink data or signalling over 3GPP access from the network apparatus (202) to the UE (102). The access type indicator, marked as 3GPP access, serves as a parameter in communication systems to specify the network access technology utilized by the UE (102) for connecting to the core network. When this indicator is set to 3GPP access, it indicates that the connection is established via a radio access technology that adheres to 3GPP standards. Further, the pending downlink data or signalling refers to information or control messages that are in a queue, awaiting delivery from the network apparatus (202) to the UE (102).

[0256] The UE (102) operates in 5GMM-IDLE mode when utilizing 3GPP access and transitions to 5GMM-CONNECTED mode when using non-3GPP access (302). In the 5GMM-IDLE mode, the UE (102) is not engaged in active data transfer with the 5G Core (5GC) but remains registered with the network apparatus (202). It periodically updates its location to the network apparatus (202) through Tracking Area Updates (TAU). While in 5GMM-IDLE mode over 3GPP access, the UE (102) maintains registration via 3GPP-defined access technologies while conserving power in an idle state. Conversely, in 5GMM-CONNECTED mode, the UE (102) establishes an active connection with the network apparatus (202), enabling real-time data transmission. Mobility is facilitated through handovers rather than periodic updates, providing a smooth user experience.

[0257] At step (1206), the UE (102) determines whether the DC maximum time offset timer associated with the UE (102) is running upon receiving the notification message. At step (1208), the UE (102) then stops the DC maximum time offset timer when it is determined to be running.

[0258] At step (1310), the UE (102) initiates the NAS signaling procedure over 3GPP access for reception of the pending downlink data or downlink signaling from the network apparatus (202). The NAS signalling procedure involves the transmission of signalling messages between the UE (102) and the network apparatus (202) to facilitate mobility management, session setup, and security measures. These procedures operate over a control plane and are not tied to any particular radio access technology (RAT). NAS signalling plays a crucial role in ensuring that the UE (102) remains connected to the network apparatus (202) as it transitions between various cells or access types. This procedure is triggered only after the DC maximum time offset timer has been halted. During the operation of this timer, the UE (102) does not initiate any NAS signalling when utilizing NR satellite access or a public land mobile network (PLMN).

[0259] Fig. 13 is a flow diagram that illustrates a method for handling downlink data or downlink signaling during a satellite communication from the network apparatus according to an embodiment as disclosed herein. The method includes steps 1302 to 1308. Each step is explained in further detail below.

[0260] At step 1302, the network apparatus (202) determines to deliver data to the UE (102) during the DC period. The phrase "DC period" describes situations in which signal coverage is inconsistent or unstable, resulting in connectivity interruptions. This phenomenon can arise from several factors, such as the movement of the UE (102) and the characteristics of the surrounding environment.

[0261] At step 1304, the network apparatus (202) transmits a notification message to the UE (102) over the non-3GPP access (302). The notification message acts as a crucial communication signal, signifying that there is downlink data or signalling awaiting transmission from the network apparatus (202) to the UE (102). This downlink data can encompass a range of information, including user data, control messages, or updates vital for sustaining the connection and optimizing the performance of the user equipment. Additionally, the notification message features an access type indicator, which is tailored to comply with the standards established by the 3GPP, the organization tasked with developing telecommunications protocols.

[0262] At step (1306), the network apparatus (202) detects initiation of the NAS signalling procedure from the UE (102) after sending the notification message. This process is crucial for initiating or sustaining a connection, ensuring that the UE (102) can communicate efficiently with the network apparatus (202).

[0263] At step 1308, the network apparatus (202) then transmits the pending downlink data or downlink signalling to the UE (102) after initiation of the NAS signalling procedure. This downlink data may contain critical information, including updates, configuration parameters, or other essential signalling that the UE (102) needs to maintain its functionality within the network apparatus (202).

[0264] In an embodiment, the UE (102) attach / register handler handles the UE (102) registration, when feeder link is not available and the UE (102) is not registered in current TAI or has lost the registration context / Network (NW) Context.

[0265] 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, g-nodeB with e-nodeB, UDM with the HSS (1102) etc. But the principles of the solution remains same.

[0266] The solutions which are defined for E-UTRA / LTE are also applicable to other RATs like 5GS(NR) or NG-RAN, the corresponding CN entities needs to be replaced b for e.g. AMF with MME, g-nodeB with e-nodeB, UDM with the HSS (1102) etc. But principles of the solution remains same

[0267] The network used in this embodiment is explained using any 5G Core Network Function for e.g. AMF or LTE core network function like MME. 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.

[0268] The messages used or indicated in this embodiment are shown as an example. The messages could be any signalling messages between the UE (102) and the Network Functions / Entities or between different Network functions / entities.

[0269] Fig. 14 is a block diagram of a terminal (or a user equipment (UE)), according to embodiments of the present disclosure. Fig. 14 corresponds to the example of the UE of Fig. 1.

[0270] 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.

[0271] 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.

[0272] 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.

[0273] 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.

[0274] 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.

[0275] Fig. 15 is a block diagram of a base station, according to embodiments of the present disclosure. Fig. 15 corresponds to the example of the eNB of Fig. 6.

[0276] As shown in Fig. 15, the base station according to an embodiment may include a transceiver 1510, a memory 1520, and a processor 1530. The transceiver 1510, the memory 1520, and the processor 1530 of the base station may operate according to a communication method of the base station described above. However, the components of the base station are not limited thereto. For example, the base station 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.

[0277] The transceiver 1510 collectively refers to a base station receiver and a base station transmitter, and may transmit / receive a signal to / from a terminal or a network entity. The signal transmitted or received to or from the terminal or a network entity may include control information and data. 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.

[0278] 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.

[0279] The memory 1520 may store a program and data required for operations of the base station. Also, the memory 1520 may store control information or data included in a signal obtained by the base station. The memory 1520 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.

[0280] The processor 1530 may control a series of processes such that the base station operates as described above. For example, the transceiver 1510 may receive a data signal including a control signal transmitted by the terminal, and the processor 1530 may determine a result of receiving the control signal and the data signal transmitted by the terminal.

[0281] Fig. 16 is a block diagram of a network entity, according to embodiments of the present disclosure.

[0282] As shown in Fig. 16, the network entity according to an embodiment may include a transceiver 1610, a memory 1620, and a processor 1630. The transceiver 1610, the memory 1620, and the processor 1630 of the network entity may operate according to a communication method of the network entity described above. However, the components of the network entity are not limited thereto. For example, the network entity may include more or fewer components than those described above. In addition, the processor 1630, the transceiver 1610, and the memory 1620 may be implemented as a single chip. Also, the processor 1630 may include at least one processor.

[0283] The transceiver 1610 collectively refers to a network entity receiver and a network entity transmitter, and may transmit / receive a signal to / from a terminal or other network entity. The signal transmitted or received to or from the terminal or other network entity may include control information and data. The transceiver 1610 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 1610 and components of the transceiver 1610 are not limited to the RF transmitter and the RF receiver.

[0284] Also, the transceiver 1610 may receive and output, to the processor 1630, a signal through a wireless channel, and transmit a signal output from the processor 1630 through the wireless channel.

[0285] The memory 1620 may store a program and data required for operations of the network entity. Also, the memory 1620 may store control information or data included in a signal obtained by the network entity. The memory 1620 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.

[0286] The processor 1630 may control a series of processes such that the network entity operates as described above. For example, the transceiver 1610 may receive a data signal including a control signal transmitted by the terminal, and the processor 1630 may determine a result of receiving the control signal and the data signal transmitted by the terminal.

[0287] 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 user equipment (UE) in a wireless communication, the method comprising:starting a discontinuous coverage (DC) maximum time offset timer in response to determining that a DC period has ended during satellite communication;receiving a notification message from a network apparatus over a non-3GPP access, wherein the notification message indicates pending downlink data or downlink signaling over 3GPP access from the network apparatus to the UE;identifying whether the DC maximum time offset timer associated with the UE is running;stopping the DC maximum time offset timer in response to receiving the notification message, when the DC maximum time offset timer is determined to be running; andinitiating a non-access stratum (NAS) signaling procedure over 3GPP access for reception of the pending downlink data or downlink signaling from the network apparatus.2.The method of claim 1, wherein the notification message includes an access type indicator set to 3GPP access.3.The method of claim 1, wherein the UE is in a 5GMM-IDLE mode over 3GPP access and the UE is in 5GMM-CONNECTED mode over the non-3GPP access.4.The method of claim 1, wherein the DC maximum time offset timer is started upon returning in a satellite coverage of a tracking area (TA) in a current registration area after being out of satellite coverage due to the DC and the UE has stored a DC maximum time offset.5.The method of claim 1, wherein any NAS signaling on a NR satellite access and a public land mobile network (PLMN) is not initiated while the DC maximum time offset timer is running.6.A method performed by a network apparatus in a wireless communication system, the method comprising:identifying to deliver data to a user equipment (UE) during the DC period; andtransmitting a notification message to the UE over a non-3GPP access, wherein the notification message indicating pending downlink data or downlink signaling from the network apparatus to the UE.7.The method of claim 6, wherein the notification message includes an access type indicator set to 3GPP access.8.The method of claim 6, further comprising:detecting initiation of a NAS signaling procedure from the UE after sending the notification message; andtransmitting the pending downlink data or downlink signaling to the UE after initiation of the NAS signaling procedure.9.A user equipment (UE) in a wireless communication system, the UE comprising:a transceiver, anda controller coupled with the transceiver and configured to:start a discontinuous coverage (DC) maximum time offset timer in response to determining that a DC period has ended during satellite communication,receive a notification message from a network apparatus over a non-3GPP access, wherein the notification message indicates pending downlink data or downlink signaling over 3GPP access from the network apparatus to the UE,identify whether the DC maximum time offset timer associated with the UE is running,stop the DC maximum time offset timer in response to receiving the notification message, when the DC maximum time offset timer is determined to be running, andinitiates a non-access stratum (NAS) signaling procedure over 3GPP access for reception of the pending downlink data or downlink signaling from the network apparatus.10.The UE of claim 9, wherein the notification message includes an access type indicator set to 3GPP access.11.The UE of claim 9, wherein the UE is in a 5GMM-IDLE mode over 3GPP access and the UE is in 5GMM-CONNECTED mode over the non-3GPP access.12.The UE of claim 9, wherein the DC maximum time offset timer is started upon returning in a satellite coverage of a tracking area (TA) in a current registration area after being out of satellite coverage due to the DC and the UE has stored a DC maximum time offset.13.The UE of claim 9, wherein any NAS signaling on a NR satellite access and a public land mobile network (PLMN) is not initiated while the DC maximum time offset timer is running.14.A network apparatus in a wireless communication system, the network apparatus comprising:a transceiver, anda controller coupled with the transceiver and configured to:identify to deliver data to a UE during the DC period; andtransmit a notification message to the UE over a non-3GPP access, wherein the notification message indicating pending downlink data or downlink signaling from the network apparatus to the UE,wherein the notification message includes an access type indicator set to 3GPP access.15.The network apparatus of claim 14, wherein the controller is further configured to:detect initiation of a NAS signaling procedure from the UE after sending the notification message, andtransmit the pending downlink data or downlink signaling to the UE after initiation of the NAS signaling procedure.

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