WO2025028915A1

WO2025028915A1 - Method and apparatus for releasing n1 non-access stratum (nas) signaling connection in a wireless communication system

Info

Publication number: WO2025028915A1
Application number: PCT/KR2024/010834
Authority: WO
Inventors: Lalith KUMAR; Aman Agarwal; Sidhant JAIN; Mahmoud Watfa
Original assignee: Samsung Electronics Co Ltd
Current assignee: Samsung Electronics Co Ltd
Priority date: 2023-07-28
Filing date: 2024-07-25
Publication date: 2025-02-06
Anticipated expiration: 2026-01-28

Abstract

The disclosure relates to a 5G or 6G communication system for supporting a higher data transmission rate. Embodiments of the disclosure describe a method for releasing established N1 NAS signalling connection The method includes transmitting a registration request message to a network entity 200 to establish the N1 NAS signalling connection, wherein the registration request message includes an unavailability period duration and does not include a start of unavailability period in the registration request message. The method includes initiating, upon receiving a registration accept message, a predefined timer at a UE 100. The method includes determining whether the initiated predefined timer expiries at the UE 100. The method includes locally releasing the established N1 NAS signalling connection associated with the network entity 200 in response to determining that the initiated predefined timer expires at the UE 100.

Description

METHOD AND APPARATUS FOR RELEASING N1 NON-ACCESS STRATUM (NAS) SIGNALING CONNECTION IN A WIRELESS COMMUNICATION SYSTEM

The present disclosure generally relates to the field of wireless communication networks, and more specifically relates to a method and an apparatus for releasing an N1 Non-access stratum (NAS) signalling connection in the wireless communication network.

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

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

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

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

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

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

This summary is provided to introduce a selection of concepts, in a simplified format, that are further described in the detailed description of the disclosure. This summary is neither intended to identify key or essential inventive concepts of the invention nor is it intended for determining the scope of the invention.

According to one embodiment of the present disclosure, a method for releasing an N1 Non-access stratum (NAS) signalling connection in a wireless communication network is disclosed herein. The method includes transmitting, by a User Equipment (UE), a registration request message to a network entity to establish the N1 NAS signalling connection, wherein the registration request message includes an unavailability period duration and does not include a start of unavailability period in the registration request message. The method further includes initiating, upon receiving a registration accept message, by the UE, a predefined timer at the UE. The method further includes determining, by the UE, whether the initiated predefined timer expires at the UE. The method further includes locally releasing, by the UE, the established N1 NAS signalling connection associated with the network entity in response to determining that the initiated predefined timer expires at the UE.

According to another embodiment of the present disclosure, a method for releasing the N1 NAS signalling connection in the wireless communication network is disclosed herein. The method includes. The method includes receiving, by the network entity, the registration request message from the UE to establish the N1 NAS signalling connection, wherein the registration request message includes an unavailability period duration and does not include a start of unavailability period. The method further includes sending, by the network entity, the registration accept message to the UE in response to receiving the registration request message. The method further includes releasing, after completion of a registration procedure, by the network entity, the established N1 NAS signalling connection associated with the UE.

According to another embodiment of the present disclosure, the UE for releasing the N1 NAS signalling connection in the wireless communication network is disclosed herein. The UE includes a processor coupled with a memory and a communicator, wherein the processor includes a NAS connection management module. The NAS connection management module is configured to transmit the registration request message to the network entity to establish the N1 NAS signalling connection, wherein the registration request message includes the unavailability period duration and does not include the start of unavailability period in the registration request message. The NAS connection management module is further configured to determine whether the initiated predefined timer expires at the UE. The NAS connection management module is further configured to locally release the established N1 NAS signalling connection associated with the network entity in response to determining that the initiated predefined timer expires at the UE.

According to another embodiment of the present disclosure, the network entity for releasing the N1 NAS signalling connection in the wireless communication network is disclosed herein. The network entity includes a processor coupled with a memory and a communicator, wherein the processor includes a NAS connection management module. The NAS connection management module is configured to receive the registration request message from the UE to establish the N1 NAS signalling connection, wherein the registration request message includes an unavailability period duration and does not include a start of unavailability period. The NAS connection management module is further configured to send the registration accept message to the UE in response to receiving the registration request message. The NAS connection management module is further configured to release, after completion of the registration procedure, the established N1 NAS signalling connection associated with the UE.

To further clarify the advantages and features of the disclosure, a more particular description of the invention will be rendered by reference to specific embodiments thereof, which are illustrated in the appended drawings. It is appreciated that these drawings depict only typical embodiments of the invention and are therefore not to be considered limiting of its scope. The invention will be described and explained with additional specificity and detail in the accompanying drawings.

Aspects of the disclosure are to address at least the above-mentioned problems and/or disadvantages and to provide at least the advantages described below. Accordingly, an aspect of the disclosure is to provide efficient communication methods in a wireless communication system.

These and other features, aspects, and advantages of the disclosure will become better understood when the following detailed description is read with reference to the accompanying drawings in which like characters represent like parts throughout the drawings, wherein:

FIG. 1 illustrates a problem scenario associated with the existing Non-access stratum (NAS) signaling mechanism, according to prior art;

FIG. 2 illustrates another problem scenario associated with the existing NAS signaling mechanism, according to prior art;

FIG. 3 illustrates a block diagram of a User Equipment (UE) for releasing an N1 NAS signalling connection in a wireless communication network, according to an embodiment as disclosed herein;

FIG. 4 illustrates a block diagram of a network entity for releasing the N1 NAS signalling connection in the wireless communication network, according to an embodiment as disclosed herein;

FIG. 5 is a sequence flow diagram illustrating a method for locally releasing established N1 NAS signalling connection associated with the network entity, according to an embodiment as disclosed herein;

FIG. 6 is a sequence flow diagram illustrating a method for releasing the established N1 NAS signalling connection associated with the UE, according to an embodiment as disclosed herein;

FIG. 7 is a flow diagram illustrating the method for locally releasing established N1 NAS signalling connection associated with the network entity, according to an embodiment as disclosed herein;

FIG. 8 is a flow diagram illustrating the method for releasing the established N1 NAS signalling connection associated with the UE, according to an embodiment as disclosed herein.

FIG. 9 illustrates a structure of a user equipment (UE), according to an embodiment as disclosed herein.

FIG. 10 illustrates a structure of a network entity, according to an embodiment as disclosed herein.

Further, skilled artisans will appreciate that elements in the drawings are illustrated for simplicity and may not have necessarily been drawn to scale. For example, the flow charts illustrate the method in terms of the most prominent steps involved to help to improve understanding of aspects of the disclosure. Furthermore, in terms of the construction of the device, one or more components of the device may have been represented in the drawings by conventional symbols, and the drawings may show only those specific details that are pertinent to understanding the embodiments of the disclosure so as not to obscure the drawings with details that will be readily apparent to those of ordinary skill in the art having the benefit of the description herein.

Aspects of the disclosure are to address at least the above-mentioned problems and/or disadvantages and to provide at least the advantages described below. Accordingly, an aspect of the disclosure is to provide a terminal and a communication method thereof in a wireless communication system.

For the purpose of promoting an understanding of the principles of the invention, reference will now be made to the embodiment illustrated in the drawings and specific language will be used to describe the same. It will nevertheless be understood that no limitation of the scope of the invention is thereby intended, such alterations and further modifications in the illustrated system, and such further applications of the principles of the invention as illustrated therein being contemplated as would normally occur to one skilled in the art to which the invention relates.

It will be understood by those skilled in the art that the foregoing general description and the following detailed description are explanatory of the invention and are not intended to be restrictive thereof.

Reference throughout this specification to “an aspect”, “another aspect” or similar language means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the disclosure. Thus, appearances of the phrase “in an embodiment”, “in one embodiment”, “in another embodiment”, and similar language throughout this specification may, but do not necessarily, all refer to the same embodiment.

The terms “comprise”, “comprising”, or any other variations thereof, are intended to cover a non-exclusive inclusion, such that a process or method that comprises a list of steps does not include only those steps but may include other steps not expressly listed or inherent to such process or method. Similarly, one or more devices or sub-systems or elements or structures or components proceeded by “comprises... a” does not, without more constraints, preclude the existence of other devices or other sub-systems or other elements or other structures or other components or additional devices or additional sub-systems or additional elements or additional structures or additional components.

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 one or more other embodiments to form new embodiments. The term “or” as used herein, refers to a non-exclusive or unless otherwise indicated. The examples used herein are intended merely to facilitate an understanding of ways in which the embodiments herein can be practiced and to further enable those skilled in the art to practice the embodiments herein. Accordingly, the examples should not be construed as limiting the scope of the embodiments herein.

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

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

Network Access Signaling (NAS) is a mechanism used to establish and manage communication sessions between a User Equipment (UE) and a network (e.g., Access and Mobility Management Function (AMF), etc.). In terrestrial networks, the NAS signaling mechanism is used to authenticate users, authorize access to network resources, and negotiate session parameters such as Quality of Service (QoS) and mobility support. This process ensures secure and efficient communication within the network. In non-terrestrial networks, such as satellite or high-altitude platform-based networks, the NAS signaling mechanism plays a crucial role in overcoming one or more challenges posed by longer propagation delays and potential intermittent connectivity. NAS signaling mechanism in these non-terrestrial networks facilitates user authentication, resource allocation, and session management, enabling seamless connectivity and mobility for users, even in remote or hard-to-reach areas where terrestrial infrastructure may be limited or unavailable. However, several problems are encountered in the existing NAS signaling mechanism associated with the non-terrestrial networks, which are mentioned below, as illustrated in FIG. 1 and FIG. 2.

FIG. 1 illustrates a problem scenario associated with the existing NAS signaling mechanism, according to prior art. In the context of a UE 10 with satellite access support, at operation 11, the UE 10 receives satellite ephemeris information from satellite 30. Using this satellite ephemeris information, the UE 10 determines its out-of-coverage period, which refers to a time when the UE 10 will be unable to maintain a connection due to satellite positioning. The problem arises when the UE 10 needs to inform the AMF/Network 20 about its upcoming an unavailability period. According to the existing NAS mechanism, at operation 12, the UE 10 sends a start of unavailability period and an unavailability period duration to the AMF/Network 20 in a registration request, a UE configuration update, or any other NAS message or indication. However, if the UE 10 does not know the exact start time of the unavailability period or if the period starts immediately, the UE 10 may only be able to provide the unavailability period duration to the AMF/Network 20. At operation 13, the UE 10 may receive a registration accept message from the AMF/Network 20 in response to sending the registration request.

At operation 14, in the case where the AMF/Network 20 receives only the unavailability period duration from the UE 10 and not the start of unavailability period, the current 3GPP specifications do not define the specific operations the AMF/Network 20 should take. This lack of clear guidance can lead to inconsistent or suboptimal handling of the UE’s satellite access limitations by the network. Additionally, if the UE 10 sends only the unavailability period duration and not the start of unavailability period to the AMF/Network 20, the current 3GPP specifications do not define the next operations the UE 10 should take, result in service disruptions, inefficient resource utilization, and a suboptimal user experience.

FIG. 2 illustrates another problem scenario associated with the existing NAS signaling mechanism, according to prior art. In the context of the UE 10 with satellite access support, the UE 10 receives the satellite ephemeris information from the satellite 30 (not shown in FIG.). Using this satellite ephemeris information or any other mechanism, the UE 10 determines its out-of-coverage period, which refers to the time when the UE 10 will be unable to get any service from the terrestrial 5G network or non- terrestrial 5G network due to satellite positioning.

At operations 21-22, in the case where the UE sends both the start of unavailability period and unavailability period duration to the AMF/Network 20, the prior art do not define the actions the AMF/Network 20 should take to inform an Application Function (AF) 40 or any other entity about the start time of the UE’s unavailability period. This information may be crucial for the AF 40 or other entities (e.g., Network Exposure Function (NEF) 30) that have subscribed to a loss of connectivity event for the UE 10. The AMF/Network 20 can inform the AF 40 or other entities about the start of the UE's unavailability period either directly or via the NEF 30.

However, the prior art do not specify the exact timing or the conditions under which the AMF/Network 20 should provide this information to the AF 40 or other entities. This can lead to inconsistent or suboptimal handling of the UE’s applications or services that rely on the UE’s connectivity. It can result in service disruptions, inefficient resource utilization, and the suboptimal user experience.

Thus, it is desired to address the above-mentioned disadvantages or other shortcomings or at least provide a useful alternative for the NAS mechanism and/or release the N1 NAS signalling connection in the wireless communication network.

Throughout this disclosure, the terms “satellite 3GPP access”, “satellite access”, “satellite access network”, “New Radio (NR) satellite access network”, “Satellite Next Generation Radio Access Network (NG-RAN) access technology”, and “NR satellite access” have been used interchangeably and have the same meaning.

Throughout this disclosure, one or more embodiments are explained using NR satellite access or satellite NG-RAN access technology as an example, but the solutions proposed are not restricted or limited to NR satellite access only. The solutions presented in this embodiment are also applicable for satellite Evolved Universal Terrestrial Radio Access Network (E-UTRAN) access technology, Narrow Band (NB)-S1 mode or Wide Band (WB)-S1 mode via satellite E-UTRAN access, and/or Narrowband Internet Of Things (NB-IOT) or Wideband Internet Of Things (WB-IOT) satellite access/architecture. Moreover, the solutions defined for NR(5GC) are also applicable to legacy Radio Access Technologies (RATs) like E-UTRA/ Long-Term Evolution (LTE), where the corresponding Core Network (CN) entities need to be replaced by LTE entities, such as replacing AMF with MME, g-NodeB with e-NodeB, and Unified Data Management (UDM) with Home Subscriber Service (HSS). However, the underlying principles of the solution remain the same.

Throughout this disclosure, the term “network” or “network entity” is explained using any 5G core network function, such as the Access and Mobility Management Function (AMF). However, the network could be any 5G/E-UTRAN core network entity, including the Session Management Function (SMF), Mobility Management Entity (MME), or User Plane Function (UPF), or the network could be any 5G/E-UTRAN Radio Access Network (RAN) Entity, such as an eNodeB (eNB), gNodeB (gNB), or NG-RAN.

Throughout this disclosure, the term Radio Access Technology (RAT) may refer to one of the following: NG-RAN (Next Generation Radio Access Network); 5G, 4G, 3G, or 2G cellular networks; EPS (Evolved Packet System) or 5GS (5G System); NR (New Radio); NR operating in unlicensed frequency bands; NR with satellite access, including NR(LEO) for Low Earth Orbit, NR(MEO) for Medium Earth Orbit, NR(GEO) for Geostationary Orbit, and NR(OTHERSAT) for other satellite access; NR RedCap (Reduced Capability); E-UTRA (Evolved UTRA, also known as LTE); E-UTRA operating in unlicensed frequency bands; NB-IoT (Narrowband Internet of Things); WB-IoT (Wideband IoT); and LTE-M (Long-Term Evolution for Machines).

Throughout this disclosure, the terms “area”, “location”, and “geographical area” used in one or more embodiments may refer to any of the following: cell/cell ID, Tracking Area Code (TAC)/Tracking Area Identity (TAI), Public Land Mobile Network (PLMN), Mobile Country Code (MCC)/Mobile Network Code (MNC), latitude/longitude, Closed Access Group (CAG) cell, or any other geographical location or coordinate.

Throughout this disclosure, the terms “camp” and “register” are used interchangeably and have the same meaning.

Throughout this disclosure, the messages used or indicated in one or more embodiments are shown as examples. The messages could be any signaling messages exchanged between the User Equipment (UE) and the Network Functions/Entities, or between different Network functions/entities. For a comprehensive list of possible Non-Access Stratum (NAS) messages, please refer to 3GPP TS 24.501 or 3GPP TS 24.301. For a list of Access Stratum (AS) messages, please refer to 3GPP TS 38.331 or 3GPP TS 36.331. An example 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;

DEREGISTRATION ACCEPT;

SERVICE REJECT;

SERVICE ACCEPT;

UE CONFIGURATION UPDATE command; and

UE PARAMETERS UPDATE command.

The specific messages used may vary depending on the context and requirements of the implementation.

Throughout this disclosure, the cause names used in one or more embodiments are for illustrative purposes only and can have any name as required. Additionally, the Non-Access Stratum (NAS) messages and Access Stratum (AS) messages described in one or more embodiments are also for illustrative purposes only. The actual NAS or AS messages used can be any of the defined protocol messages exchanged between UE and the AMF/ MME, or between the UE and the gNodeB (NG-RAN/any RAN node) or eNodeB, as per the applicable protocol specifications. The specific NAS or AS messages used may vary based on the context and requirements of the implementation, but the principles and concepts described in this disclosure remain applicable.

Throughout this disclosure, in one or more embodiments, the 5G System (5GS) registration type may include the following:

Initial registration: This is the first-time registration of the UE with the 5GS.

Mobility registration updating: This registration is performed when the UE moves to a new Tracking Area (TA) or 5G Tracking Area (5GTA) within the same Public Land Mobile Network (PLMN).

Periodic registration updating: This registration is performed by the UE at regular intervals to maintain its registration with the 5GS.

Emergency registration: This registration is used when the UE needs to access the 5GS for emergency services.

SNPN onboarding registration: This registration is used when the UE needs to register with a Stand-alone Non-Public Network (SNPN).

Disaster roaming initial registration: This registration is used when the UE needs to register with a 5GS during a disaster situation while roaming.

Disaster roaming mobility registration updating: This registration is used when the UE needs to update its registration with the 5GS during a disaster situation while roaming.

Throughout this disclosure, in one or more embodiments, the PLMN selection process is performed in accordance with the requirements specified as per 3GPP TS 23.122, without the Registered PLMN (RPLMN), which can be defined as follows: The Mobile Station (MS) selects and attempts registration on any available and allowable PLMN/access technology combinations in the following order:

Either the Home PLMN (HPLMN) (if the Equivalent HPLMN (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 a Subscriber Identity Module (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 a Mobile Equipment (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.

Throughout this disclosure, in one or more embodiments, the PLMN selection process is performed in accordance with the requirements specified in as per 3GPP TS 23.122, with the RPLMN, which can be defined as follows: The MS selects and attempts registration on any available and allowable PLMN/access technology combinations in the following order:

Either the RPLMN or a 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).

In the context of a 5G system supporting satellite access, the following technical requirements apply:

Service continuity: The 5G system supports seamless service continuity for user equipment (UE) when transitioning between the NR terrestrial access network and the NR satellite access networks. This shall be supported for scenarios where the satellite and terrestrial access networks are owned by the same operator, as well as scenarios where they are owned by two different operators with a roaming agreement in place.

Frequency band support: The 5G system supports operation of the NR satellite access network (NTN) and the terrestrial NR access network (TN) in either of the following configurations:

- Operation in different frequency bands, e.g., Frequency Range 1 (FR1) for the terrestrial network and Frequency Range 2 (FR2) for the satellite network.

- Operation in the same frequency band, e.g., both the satellite and terrestrial networks operating in FR1 or FR2.

According to prior art, in the context of support of unavailability period: Before the start of an event that makes the UE unavailable, the UE includes the following information in its signaling:

- An indication and type of the unavailability;

- The start of the unavailability period, if known;

- The duration of the unavailability period, if known.

The UE may then trigger either a mobility registration update procedure or a UE-initiated deregistration procedure.

According to 3GPP TS 23.501, Release 18, in the context of mobility management and power saving optimization: in the context of 5G NR satellite access that provides discontinuous network coverage, and when both the UE and the network indicate support for the “unavailability period support” feature, the following applies:

a. If the UE determines it will lose network coverage and decides to remain in a no-service state during the coverage loss period, then:

i. A UE out-of-coverage period may be determined, which is expressed by:

(i) The start of unavailability period indicates the timing information for when the UE is expected to be out of coverage.

(ii) The unavailability period duration indicates the timing information for when the UE is expected to regain network coverage.

The UE out-of-coverage period may consider the current and expected future locations of the UE.

To allow the network to release the N1 NAS signalling connection, the UE:

a. shall start the timer T3540 if the UE receives any of the 5GMM cause values #7, #11, #12, #13, #15, #27, or #72;

b. shall start the timer T3540 for a UE in 3GPP access if the UE receives a REGISTRATION ACCEPT message;

c. shall start the timer T3540 if the UE receives a REGISTRATION REJECT message indicating the 5GMM cause value #9 or #10;

d. shall start the timer T3540 if the UE receives a SERVICE REJECT message indicating the 5GMM cause value #9 or #10;

e. shall start the timer T3540 if the UE receives a CONFIGURATION UPDATE COMMAND message indicating registration requested;

f. shall start the timer T3540 if the UE receives a SERVICE ACCEPT message;

Upon expiry of T3540,

a. In cases of a, b, and f, the UE shall locally release the established N1 NAS signalling connection;

b. In cases of c and d, the UE shall locally release the established N1 NAS signalling connection and the UE shall initiate the registration procedure as described in subclause 5.5.1.3.5 or 5.6.1.5; or

c. In case of e, the UE shall locally release the established N1 NAS signalling connection and perform a new registration procedure as specified in subclause 5.5.1.3.2.

In the context of a loss of connectivity event subscription for the UE by the AF, Before the start of an event that makes the UE unavailable, the UE includes an indication and type of unavailability, the start of the unavailability period if known and the unavailability period duration (if known) and triggers either mobility registration update or UE initiated deregistration procedure:

a. If the UE initiates the mobility registration update procedure: If there is a “Loss of Connectivity” event subscription for the UE by the AF, the AMF considers the remaining time in the Unavailability Period (if available) when constructing the “Loss of Connectivity” event report towards the NEF and the Unavailability Period is reported to the respective subscribed AF;

b. If the UE initiates UE-initiated deregistration procedure: according to point-1, If there is the “Loss of Connectivity” event subscription for the UE by AF, the AMF considers the remaining time in the Unavailability Period when constructing the “Loss of Connectivity” event report towards the NEF and the unavailability period is reported to the respective subscribed AF.

Referring now to the drawings, and more particularly to FIGS. 3 to 8, where similar reference characters denote corresponding features consistently throughout the figures, there are shown preferred embodiments.

FIG. 3 illustrates a block diagram of a UE 100 for releasing an N1 NAS signalling connection in a wireless communication network, according to an embodiment as disclosed herein. Examples of the UE 100 may include, but are not limited to, a smartphone, a tablet computer, a Personal Digital Assistance (PDA), an Internet of Things (IoT) device, a wearable device, etc.

In one or more embodiments, the UE 100 comprises a system 101. The system 101 may include a memory 110, a processor 120, and a communicator 130. The system 101 may be implemented on one or multiple electronic devices (not shown in FIG.).

In an embodiment, the memory 110 stores instructions to be executed by the processor 120 for releasing the N1 NAS signalling connection in the wireless communication network, as discussed throughout the disclosure. The memory 110 may include non-volatile storage elements. Examples of such non-volatile storage elements may include magnetic hard discs, optical discs, floppy discs, flash memories, or forms of electrically programmable memories (EPROM) or electrically erasable and programmable (EEPROM) memories. In addition, the memory 110 may, in some examples, be considered a non-transitory storage medium. The term “non-transitory” may indicate that the storage medium is not embodied in a carrier wave or a propagated signal. However, the term “non-transitory” should not be interpreted that the memory 110 is non-movable. In some examples, the memory 110 can be configured to store larger amounts of information than the memory. In certain examples, a non-transitory storage medium may store data that can, over time, change (e.g., in Random Access Memory (RAM) or cache). The memory 110 can be an internal storage unit, or it can be an external storage unit of the UE 100, a cloud storage, or any other type of external storage.

The processor 120 communicates with the memory 110 and the communicator 130. The processor 120 is configured to execute instructions stored in the memory 110 and to perform various processes for releasing the N1 NAS signalling connection in the wireless communication network, as discussed throughout the disclosure. The processor 120 may include one or a plurality of processors, 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).

In one or more embodiments, the processor 120 may include a NAS connection management module 121. The NAS connection management module 121 is implemented by processing circuitry such as logic gates, integrated circuits, microprocessors, microcontrollers, memory circuits, passive electronic components, active electronic components, optical components, hardwired circuits, or the like, and may optionally be driven by firmware. The circuits may, for example, be embodied in one or more semiconductor chips, or on substrate supports such as printed circuit boards and the like.

In one or more embodiments, NAS connection management module 121 is configured to perform one or more operations for releasing the N1 NAS signalling connection in the wireless communication network, when the UE 100 has knowledge or shares information about an unavailability period duration, but not a start of unavailability period, as described below and as illustrated in FIG. 5.

The NAS connection management module 121 may receive satellite coverage availability information from a satellite or any other network entity. Upon receiving this satellite coverage availability information, the NAS connection management module 121 may determine a value of the unavailability period duration and/or a value of the start of unavailability period based on the received satellite coverage availability information or based on any other mechanism.

Consider a scenario where the UE 100 transmits a registration request message to a network entity (e.g., AMF), to establish the N1 NAS signaling connection. In this scenario, the UE 100 includes the unavailability period duration but does not include the start of unavailability period in the registration request message. The NAS connection management module 121 may then receive a registration accept message from the network entity in response to the registration request message. Subsequently, the NAS connection management module 121 may initiate a predefined timer, such as the T3540 timer, upon receiving the registration accept message. The NAS connection management module 121 may then monitor the expiration of the initiated predefined timer. If the NAS connection management module 121 determines that the initiated predefined timer has expired, the NAS connection management module 121 may locally release the established N1 NAS signaling connection associated with the network entity. This procedure allows the UE 100 to inform the network about the upcoming unavailability period, enabling the network entity to adjust its operations accordingly. The local release of the N1 NAS signaling connection upon timer expiration ensures that the UE 100 can efficiently manage its connectivity with the network entity during periods of satellite coverage unavailability. The UE 100 can enter into power saving state during unavailability period, though network has not released the NAS signaling connection.

In one or more embodiments, the NAS connection management module 121 may receive the registration accept message from the network entity in response to sending the registration request message. Upon receiving the registration accept message, the NAS connection management module 121 may determine at least one of (a) whether the received registration accept message comprises the start of unavailability period, (b) whether the network entity indicates the start of unavailability period determined by the network entity, and (c) whether the network entity indicates a current time is the start of unavailability period determined by the network entity. The NAS connection management module 121 may initiate the predefined timer at the UE 100 in response to determining that, one of, (a) the received registration accept message does not comprise the start of unavailability period, (b) the network entity does not indicate the start of unavailability period determined by the network entity, or (c) the network entity indicates the current time is the start of unavailability period determined by the network entity.

The communicator 130 is configured for communicating internally between internal hardware components and with external devices (e.g., server, network entity, etc.) via one or more networks (e.g., radio technology). The communicator 130 includes an electronic circuit specific to a standard that enables wired or wireless communication.

Although FIG. 3 shows various hardware components of the UE 100, but it is to be understood that other embodiments are not limited thereon. In other embodiments, the UE 100 may include less or more number of components. Further, the labels or names of the components are used only for illustrative purposes and do not limit the scope of the invention. One or more components can be combined to perform the same or substantially similar functions to release the N1 NAS signalling connection in the wireless communication network.

FIG. 4 illustrates a block diagram of the network entity 200 for releasing the N1 NAS signalling connection in the wireless communication network, according to an embodiment as disclosed herein. Examples of the network entity 200 may include, but are not limited to, an Access and Mobility Management Function (AMF), a Session Management Function (SMF), a Mobility Management Entity (MME), or a User Plane Function (UPF), or the network entity 200 could be any 5G/E-UTRAN Radio Access Network (RAN) Entity, such as an eNodeB (eNB), gNodeB (gNB), or NG-RAN.

In one or more embodiments, the network entity 200 comprises a system 201. The system 201 may include a memory 210, a processor 220, and a communicator 230. The system 201 may be implemented on one or multiple electronic devices (not shown in FIG.).

In an embodiment, the memory 210 stores instructions to be executed by the processor 220 for releasing the N1 NAS signalling connection in the wireless communication network, as discussed throughout the disclosure. The memory 210 may include non-volatile storage elements. Examples of such non-volatile storage elements may include magnetic hard discs, optical discs, floppy discs, flash memories, or forms of electrically programmable memories (EPROM) or electrically erasable and programmable (EEPROM) memories. In addition, the memory 210 may, in some examples, be considered a non-transitory storage medium. The term “non-transitory” may indicate that the storage medium is not embodied in a carrier wave or a propagated signal. However, the term “non-transitory” should not be interpreted that the memory 210 is non-movable. In some examples, the memory 210 can be configured to store larger amounts of information than the memory. In certain examples, a non-transitory storage medium may store data that can, over time, change (e.g., in Random Access Memory (RAM) or cache). The memory 210 can be an internal storage unit, or it can be an external storage unit of the network entity 200, a cloud storage, or any other type of external storage.

The processor 220 communicates with the memory 210 and the communicator 230. The processor 220 is configured to execute instructions stored in the memory 210 and to perform various processes for releasing the N1 NAS signalling connection in the wireless communication network, as discussed throughout the disclosure. The processor 220 may include one or a plurality of processors, 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).

In one or more embodiments, the processor 220 may include a NAS connection management module 221. The NAS connection management module 221 is implemented by processing circuitry such as logic gates, integrated circuits, microprocessors, microcontrollers, memory circuits, passive electronic components, active electronic components, optical components, hardwired circuits, or the like, and may optionally be driven by firmware. The circuits may, for example, be embodied in one or more semiconductor chips, or on substrate supports such as printed circuit boards and the like.

In one or more embodiments, the NAS connection management module 221 is configured to perform one or more operations for releasing the N1 NAS signalling connection in the wireless communication network, when the UE 100 has knowledge or shares information about the unavailability period duration, but not the start of unavailability period, as described below and as illustrated in FIG. 5.

In one or more embodiments, the NAS connection management module 221 may receive the registration request message from the UE 100 to establish the N1 NAS signalling connection. The registration request message includes the unavailability period duration and does not include the start of unavailability period. The NAS connection management module 221 may then send the registration accept message to the UE 100 in response to receiving the registration request message. The NAS connection management module 221 may then release, after completion of a registration procedure, by the network entity 200, the established N1 NAS signalling connection associated with the UE 100.

In one or more embodiments, the NAS connection management module 221 may determine (a) whether the received registration request message includes both the unavailability period duration and the start of unavailability period, and (b) whether the registration procedure was successfully completed with the UE 100. The NAS connection management module 221 may release the established N1 NAS signalling connection associated with the UE 100 in response to determining that (a) the received registration request message includes the unavailability period duration and does not include the start of unavailability period, and (b) the registration procedure successfully completes with the UE 100.

In one or more embodiments, consider a scenario where the UE 100 has knowledge or shares information about both the unavailability period duration and/or the start of unavailability period, then the NAS connection management module 221 may perform one or more operations for releasing the N1 NAS signalling connection in the wireless communication network as described below and as illustrated in FIG. 6.

The NAS connection management module 221 may detect and indicate a loss of connectivity event to at least one of a Network Exposure Function (NEF) and Application Function (AF) based on one or more predefined conditions, as mentioned below.

a. when the UE 100 includes the unavailability period duration and does not include the start of unavailability period during the registration procedure or deregistration procedure or any other NAS procedure;

b. when the unavailability period duration starts based on the start of unavailability period stored in a UE context at the network entity 200.

The communicator 230 is configured for communicating internally between internal hardware components and with external devices (e.g., server, UE, etc.) via one or more networks (e.g., radio technology). The communicator 230 includes an electronic circuit specific to a standard that enables wired or wireless communication.

Although FIG. 4 shows various hardware components of the network entity 200, but it is to be understood that other embodiments are not limited thereon. In other embodiments, the network entity 200 may include less or more number of components. Further, the labels or names of the components are used only for illustrative purposes and do not limit the scope of the invention. One or more components can be combined to perform the same or substantially similar functions to release the N1 NAS signalling connection in the wireless communication network.

FIG. 5 is a sequence flow diagram illustrating a method 500 for locally releasing established N1 NAS signalling connection associated with the network entity 200, according to an embodiment as disclosed herein. The method 500 described in FIG. 5 provides a solution to the problem scenario that is illustrated in FIG. 1. The method 500 may execute multiple operations for locally releasing established N1 NAS signalling connection associated with the network entity 200, which are given below.

At operation 501, the UE 100 receives the satellite coverage availability information from the satellite or Satellite Coverage Availability Function (SCAF) 300. The UE 100 then determines the value of the unavailability period duration and the value of the start of unavailability period based on the received satellite coverage availability information or any other mechanisms at the UE 100. At

operations

502, 503, and 504, the UE 100 transmits the registration request message to the AMF/network entity 200 to establish the N1 NAS signalling connection, indicate the unavailability period information to network entity and perform the one of the following operations.

a. If UE 100 includes the unavailability period duration but the start of unavailability period is not included in the registration request message or any other message or indication, then UE 100 may start timer T3540, upon receiving the registration accept message or indication. Optionally, the UE 100 may start timer T3540 when the registration accept message does not include the start time or network indicates there is no start time determined by the network or the current time is the start time determined by the network.

b. Otherwise, if UE 100 includes the unavailability period duration and start of unavailability period in the registration request message or any other message or indication, then UE 100 may not start timer T3540, upon receiving the registration accept message or indication. Optionally, the UE 100 may not start timer T3540 if the registration accept message does include the start timer (e.g., this indicates a future time of start of unavailabity) or the start time indicates the current time is not the start of unavailability period.

At operations 504 and 505, upon the expiry of the timer T3540, the UE 100 may locally release the established N1 NAS signalling connection. This implies the UE 100 has not received the NAS/RRC signaling connection release from the network before the expiry of the predefined timer(i.e., T3540) and from UE perspective the network side the connection is still intact and network has not released the N1 NAS signaling connection as expected, thus the UE 100 may perform local release so that the UE 100 can enter into unavailability and perform power saving.

At operation 506, if the unavailability period duration is included but the start of unavailability period is not included in the received registration request message or any other message or indication then the AMF/network entity 200 may trigger the NAS signalling connection release for the UE 100 after sending the registration accept message or other message or completing the registration procedure. Optionally, AMF/network entity 200 may trigger the NAS signalling connection release if the AMF/network entity 200 determines that unavailability period is started immediately based on the indication of the UE 100 or AMF internal determination.

If the unavailability period duration and the start of unavailability period are included in the received registration request or any other message or indication then the AMF/network entity 200 may not trigger NAS signalling connection release for the UE 100 after sending the registration accept message or other message.

In one embodiment, at the start time, the AMF/network entity 200 may release the NAS signalling connection optionally early enough to complete the procedure before the UE 100 goes out-of-coverage. The UE 100 may start the T3540 timer when the start time occurs, the start time can be the time at which the unavailability of the UE 100 has started.

In one embodiment, the UE 100 and AMF/network entity 200 may set the start timer with a buffer to execute the NAS signalling release procedure.

FIG. 6 is a sequence flow diagram illustrating a method 600 for releasing the established N1 NAS signalling connection associated with the UE 100, according to an embodiment as disclosed herein. The method 600 described in FIG. 6 provides a solution to the problem scenario that is illustrated in FIG. 2. The method 600 may execute multiple operations for releasing established N1 NAS signalling connection associated with the UE 100, which are given below.

At

operations

601 and 602, as option-1 (OPT-1), the AMF/network entity 200 may receive the start of unavailability period and unavailability period duration from the UE 100. The AMF/network entity 200 then directly or indirectly via a Network Exposure Function (NEF) 600a indicates to an Application Function (AF) 600b when it receives the start of unavailability period from the UE 100. Additionally, the AMF/network entity 200 communicates the value of the start of unavailability period as indicated by the UE 100.

For example, if the UE 100 sends the start of unavailability period as a time that is 1 hour away from the current time, the AMF/network entity 200 will indicate to the AF 600b directly or via the NEF 600a at the current time that the start of the unavailability period is 1 hour away. If there is a “Loss of Connectivity” event subscription for the UE 100 by the AF 600b, the AMF/network entity 200 considers the unavailability period and start time when constructing the “Loss of Connectivity” event report towards the NEF 600a. The unavailability period is then reported to the respective subscribed AF 600b.

If the AF 600b subscribes for the “Loss of Connectivity” event before the start of the unavailability period, the AMF/network entity 200 will report the remaining time of the unavailability period when constructing the "Loss of Connectivity" event report towards the NEF 600a. Additionally, the start time can be reported using at least one of the defined mechanisms, such as the remaining time difference or the absolute time.

In one or more embodiments, the start of unavailability period if included by the UE 100 may be encoded in any form below:

a. Absolute date and time;

b. Time difference from a mutually agreed date and time;

c. Time difference from a standard date and time;

d. Time difference w.r.t. a message or signal. i.e., the time is measured from the time at which the registration request or any other message or indication containing the start of unavailability period IE is received.

In one or more embodiments, the start of unavailability period (or start time) as determined by the network may be encoded in any form below:

a. Absolute date and time;

b. Time difference from a mutually agreed date and time;

c. Time difference from a standard date and time;

d. Time difference i.e., remaining time w.r.t. a message or signal received. i.e., the time is measured with a difference between the time at which the registration request or any other message or indication containing the start of unavailability period IE is received and the time at which AF subscribes for loss of connectivity event.

At

operations

603 and 604, as option-2 (OPT-2), the AMF/network entity 200 may receive the start of unavailability period and unavailability period duration from the UE 100. The AMF/network entity 200 indicates to the AF 600b directly or via the NEF 600a when the start of unavailability period, as indicated by the UE 100 or as determined by the AMF/network entity 200, has occurred (i.e., the time becomes equal to the start of unavailability period indicated by the UE 100 or as determined by the AMF/network entity 200).

For example, if the UE 100 sends the start of unavailability period as a time that is 1 hour away from the current time, the AMF/network entity 200 will indicate to the AF 600b directly or via the NEF 600a at the time that is 1 hour away from the current time, i.e., at the start of the unavailability period, that the UE 100 is going out of coverage.

When the start time of the unavailability period occurs, if there is a “Loss of Connectivity” event subscription for the UE 100 by the AF 600b, the AMF/network entity 200 includes the unavailability period when constructing the "Loss of Connectivity" event report towards the NEF 600a, and the Unavailability Period is reported to the respective subscribed AF 600b.

If the unavailability period has already started and the AF 600b subsequently subscribes to the “Loss of Connectivity” event, the AMF/network entity 200 reports the remaining time of the unavailability period when constructing the “Loss of Connectivity” event report towards the NEF 600a.

For example: Preconditions: the UE 100 reports the start time as 1 hour from the message sent time. Message sent time is at 12:00. Unavailability duration is 12 hours.

a. At 13:00 (1 hour from the message sent time), the AMF/network entity 200 (or any other Network Function) will report the unavailability duration as 12 hours to the AF 600b, optionally via the NEF 600a.

b. If the AF 600b subscribes to the “Loss of Connectivity” event at 14:00, then the AMF/network entity 200 indicates the remaining unavailability period of 11 hours (i.e., remaining time) when constructing the “Loss of Connectivity” event report.

At operations 605 and 606, as option-3 (OPT-3), the AMF/network entity 200 does not receive the start of unavailability period from the UE 100. The AMF/network entity 200 then indicates to the AF 600b directly or via NEF 600a immediately when the start time is not included by the UE 100 that the UE 100 is going out of coverage now.

For Example, when the UE 100 does not include start of unavailability period in the registration request message or any other message, the AMF/network entity 200 indicates loss of connectivity to the AF 600b or sends any other indication to the AF 600b that start of unavailability period is not included by the UE 100. When the start time is not included by the UE 100, if there is “Loss of Connectivity” event subscription for the UE 100 by the AF 600b, the AMF/network entity 200 considers the remaining time in the unavailability period when constructing the “Loss of Connectivity” event report towards the NEF 600a and the unavailability period is reported to the respective subscribed AF 600b.

For example: Preconditions: the UE 100 does not include start time, Message sent time is at 12:00, and Unavailability duration is 12 hours.

a. Then AMF/network entity 200 (or any other NF) will report the unavailability duration as 12 hours to the AF 600b optionally via NEF 600a. Optionally, the AMF/network entity 200 can trigger this at the AMF/network entity 200 determined start time after calculating the remaining time of the unavailability duration.

b. If an AF subscribes the “Loss of Connectivity” at 2 O clock then the AMF/network entity 200 indicates the unavailability period when constructing the “Loss of Connectivity” event, the unavailability period is 10 hours (i.e., remaining time).

For reporting purposes in this embodiment, the AMF/network entity 200 may use the unavailability period/start timer as indicated by the UE 100 or as determined by the AMF/network entity 200 and follow the steps as described in this embodiment while calculating the remaining time or absolute time or time to report unavailability period.

FIG. 7 is a flow diagram illustrating the method 700 for locally releasing established N1 NAS signalling connection associated with the network entity 200, according to an embodiment as disclosed herein. The method 700 may execute multiple operations for locally releasing established N1 NAS signalling connection associated with the network entity 200, which are given below.

At operation 701, the method 700 includes transmitting the registration request message to the network entity 200 to establish the N1 NAS signalling connection and indicate unavailability information, wherein the registration request message includes the unavailability period duration and does not include the start of unavailability period in the registration request message. At operation 702, the method 700 includes initiating, upon receiving the registration accept message, the predefined timer at the UE 100. At operation 703, the method 700 includes determining whether the initiated predefined timer expiries at the UE 100. At operation 704, the method 700 includes locally releasing the established N1 NAS signalling connection associated with the network entity in response to determining that the initiated predefined timer expires at the UE 100. Further, a detailed description related to the various operations of FIG. 7 is covered in the description related to FIG. 3, FIG. 4, and FIG. 5, and is omitted herein for the sake of brevity.

FIG. 8 is a flow diagram illustrating the method 800 for releasing the established N1 NAS signalling connection associated with the UE 100, according to an embodiment as disclosed herein. The method 800 may execute multiple operations for releasing established N1 NAS signalling connection associated with the UE 100, which are given below.

At operation 801, the method 800 includes receiving the registration request message from the UE 100 to establish the N1 NAS signalling connection, wherein the registration request message includes the unavailability period duration and does not include the start of unavailability period. At operation 802, the method 800 includes sending the registration accept message to the UE 100 in response to receiving the registration request message. At operation 803, the method 800 includes releasing, after completion of the registration procedure the established N1 NAS signalling connection associated with the UE 100. Further, a detailed description related to the various operations of FIG. 8 is covered in the description related to FIG. 3, FIG. 4, and FIG. 5, and is omitted herein for the sake of brevity.

The disclosed method(s) has several advantages over the existing method, for example, which are stated below.

a. Simplified connection management: The UE 100 can autonomously manage the lifecycle of the N1 NAS signaling connection based on the predefined timer, without the need for additional signaling with the network entity 200. This simplifies the connection management process and reduces the complexity on both the UE 100 and network side.

b. Improved power efficiency: By locally releasing the connection when the predefined timer expires, the UE 100 can conserve battery power and resources, as it does not have to maintain the connection indefinitely. This is particularly beneficial for battery-powered UEs, where power efficiency is a crucial consideration.

c. Reduced signaling latency: The local release of the N1 NAS signaling connection by the UE 100 eliminates the need for additional signaling interactions with the network entity to release the connection. This can help reduce the overall signaling latency, improving the responsiveness and user experience.

d. Increased scalability: By offloading the connection release process to the UE 100, the network entity 200 is relieved from the burden of managing a large number of signaling connections. This can enhance the overall scalability of the system, allowing it to handle a higher volume of UEs and connections more efficiently.e. Seamless connectivity transition: The ability to locally release the connection when the predefined timer expires can facilitate smoother transitions between different connectivity states, such as moving from an active state to an inactive or unavailable state. This can help ensure a more seamless user experience during these transitions.

As shown in FIG. 9, the UE according to an embodiment may include a transceiver 910, a memory 920, and a processor 930. The transceiver 910, the memory 920, and the processor 930 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 930, the transceiver 910, and the memory 920 may be implemented as a single chip. Also, the processor 930 may include at least one processor. Furthermore, the UE of FIG. 9 corresponds to the UE of the FIG. 3.

The transceiver 910 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 910 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 910 and components of the transceiver 910 are not limited to the RF transmitter and the RF receiver.

Also, the transceiver 910 may receive and output, to the processor 930, a signal through a wireless channel, and transmit a signal output from the processor 930 through the wireless channel.

The memory 920 may store a program and data required for operations of the UE. Also, the memory 920 may store control information or data included in a signal obtained by the UE. The memory 920 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.

The processor 930 may control a series of processes such that the UE operates as described above. For example, the transceiver 910 may receive a data signal including a control signal transmitted by the base station or the network entity, and the processor 930 may determine a result of receiving the control signal and the data signal transmitted by the base station or the network entity.

As shown in FIG. 10, the network entity includes a transceiver 1010, a memory 1020, and a processor 1030. The transceiver 1010, the memory 1020, and the processor 1030 of the network entity may operate according to a communication method of the network entity described above. However, the components of the terminal network entity are not limited thereto. For example, the network entity may include fewer or a greater number of components than those described above. In addition, the processor 1030, the transceiver 1010, and the memory 1020 may be implemented as a single chip. Also, the processor 1030 may include at least one processor.

The network entity includes at least one entity of a core network. For example, the network entity includes an Access and mobility management function (AMF), a session management function (SMF), a policy control function (PCF), a network repository function (NRF), a user plane function (UPF), a network slicing selection function (NSSF), an authentication server function (AUSF), a unified data management (UDM) and a network exposure function (NEF), but the network entity is not limited thereto. For example, the network entity includes a base station (BS).

The transceiver 1010 collectively refers to a network entity receiver and a network entity transmitter, and may transmit/receive a signal to/from a base station or a UE. The signal transmitted or received to or from the base station or the UE may include control information and data. In this regard, the transceiver 1010 may include an RF transmitter for up-converting and amplifying a frequency of a transmitted signal, and an RF receiver for amplifying low-noise and down-converting a frequency of a received signal. However, this is only an example of the transceiver 1010 and components of the transceiver 1010 are not limited to the RF transmitter and the RF receiver.

The transceiver 1010 may receive and output, to the processor 1030, a signal through a wireless channel, and transmit a signal output from the processor 1030 through the wireless channel.

The memory 1020 may store a program and data required for operations of the network entity. Also, the memory 1020 may store control information or data included in a signal obtained by the network entity. The memory 1020 may be a storage medium, such as a ROM, a RAM, a hard disk, a CD-ROM, and a DVD, or a combination of storage media.

The processor 1030 may control a series of processes such that the network entity operates as described above. For example, the transceiver 1010 may receive a data signal including a control signal, and the processor 1030 may determine a result of receiving the data signal.

The various actions, acts, blocks, steps, or the like in the sequence/flow diagrams may be performed in the order presented, in a different order, or simultaneously. Further, in some embodiments, some of the actions, acts, blocks, steps, or the like may be omitted, added, modified, skipped, or the like without departing from the scope of the invention.

In various embodiment, a method (700) for releasing an N1 Non-access stratum (NAS) signalling connection in a wireless communication network, the method (700) comprising: transmitting (701), by a User Equipment (UE) (100), a registration request message to a network entity (200) to establish the N1 NAS signalling connection, wherein the registration request message includes an unavailability period duration and does not include a start of unavailability period in the registration request message; initiating (702), upon receiving a registration accept message, by the UE (100), a predefined timer at the UE (100); determining (703), by the UE (100), whether the initiated predefined timer expiries at the UE (100); and locally releasing (704), by the UE (100), the established N1 NAS signalling connection associated with the network entity (200) in response to determining that the initiated predefined timer expires at the UE (100).

In an embodiment, The method (700), prior to transmitting the registration request message comprises: receiving, by the UE (100), a satellite coverage availability information from an application function; and determining, by the UE (100), a value of the unavailability period duration and a value of the start of unavailability period based on the received satellite coverage availability information.

In an embodiment, The method (700), wherein initiating the predefined timer at the UE (100) comprises: receiving, by the UE (100), the registration accept message from the network entity (200) in response to sending the registration request message; determining, by the UE (100), at least one of: whether the received registration accept message comprises the start of unavailability period, or whether the network entity (200) indicates the start of unavailability period determined by the network entity (200), or whether the network entity (200) indicates a current time is the start of unavailability period determined by the network entity (200); and initiating, by the UE (100), the predefined timer at the UE (100) in response to determining that the received registration accept message does not comprise the start of unavailability period, or the network entity (200) indicates the current time is the start of unavailability period determined by the network entity (200).

In an embodiment, A method (800) for releasing an N1 Non-access stratum (NAS) signalling connection in a wireless communication network, the method (800) comprising: receiving (801), by a network entity (200), a registration request message from a User Equipment (UE) (100) to establish the N1 NAS signalling connection, wherein the registration request message includes an unavailability period duration and does not include a start of unavailability period; sending (802), by the network entity (200), a registration accept message to the UE (100) in response to receiving the registration request message; releasing (803), after completion of a registration procedure, by the network entity (200), the established N1 NAS signalling connection associated with the UE (100).

In an embodiment, The method (800), wherein releasing the established N1 NAS signalling connection associated with the UE (100) comprises: determining, by the network entity (200), whether the received registration request message includes both the unavailability period duration and the start of unavailability period, and whether the registration procedure was successfully completed with the UE (100); and releasing, by the network entity (200), the established N1 NAS signalling connection associated with the UE (100) in response to determining that the received registration request message includes the unavailability period duration and does not include the start of unavailability period, and the registration procedure successfully completes with the UE (100).

In an embodiment, The method (800), comprising: detecting and indicating, by the network entity (200), a loss of connectivity event to at least one of a Network Exposure Function (NEF) and Application Function (AF) based on one or more predefined conditions comprise: when the UE (100) includes the unavailability period duration and does not include the start of unavailability period during the registration procedure or deregistration procedure; or when the unavailability period duration starts based on the start of unavailability period stored in a UE context at the network entity (200).

In an embodiment, A User Equipment (UE) (100) for releasing an N1 Non-access stratum (NAS) signalling connection in a wireless communication network, wherein the UE (100) comprising: a memory (110); a communicator (130); and a processor (120) include a NAS connection management module (121), operably connected to the memory (110) and the communicator (130), configured to: transmit a registration request message to a network entity (200) to establish the N1 NAS signalling connection, wherein the registration request message includes an unavailability period duration and does not include a start of unavailability period in the registration request message; initiate, upon receiving a registration accept message, a predefined timer at the UE (100); determine, by the UE (100), whether the initiated predefined timer expiries at the UE (100); and locally release the established N1 NAS signalling connection associated with the network entity (200) in response to determining that the initiated predefined timer expires at the UE (100).

In an embodiment, The UE (100), prior to transmitting the registration request message, the NAS connection management module (121) is configured to: receive a satellite coverage availability information from an application function; and determine a value of the unavailability period duration and a value of the start of unavailability period based on the received satellite coverage availability information.

In an embodiment, The UE (100), wherein to initiate the predefined timer at the UE (100), the NAS connection management module (121) is configured to: receive the registration accept message from the network entity (200) in response to sending the registration request message; determine at least one of: whether the received registration accept message comprises the start of unavailability period, or whether the network entity (200) indicates the start of unavailability period determined by the network entity (200), or whether the network entity (200) indicates a current time is the start of unavailability period determined by the network entity (200); and initiate the predefined timer at the UE (100) in response to determining that the received registration accept message does not comprise the start of unavailability period, or the network entity (200) indicates the current time is the start of unavailability period determined by the network entity (200).

In an embodiment, A network entity (200) for releasing an N1 Non-access stratum (NAS) signalling connection in a wireless communication network, wherein the network entity (200) comprising: a memory (210); a communicator (230); and a processor (220) include a NAS connection management module (221), operably connected to the memory (210) and the communicator (230), configured to: receive a registration request message from a User Equipment (UE) (100) to establish the N1 NAS signalling connection, wherein the registration request message includes an unavailability period duration and does not include a start of unavailability period; send a registration accept message to the UE (100) in response to receiving the registration request message; release, after completion of a registration procedure, the established N1 NAS signalling connection associated with the UE (100).

In an embodiment, The network entity (200), wherein to release the established N1 NAS signalling connection associated with the UE (100), the NAS connection management module (221) is configured to: determine whether the received registration request message includes both the unavailability period duration and the start of unavailability period, and whether the registration procedure was successfully completed with the UE (100); and release the established N1 NAS signalling connection associated with the UE (100) in response to determining that the received registration request message includes the unavailability period duration and does not include the start of unavailability period, and the registration procedure successfully completes with the UE (100).

In an embodiment, The network entity (200), the NAS connection management module (221) is configured to: detect and indicate a loss of connectivity event to at least one of a Network Exposure Function (NEF) and Application Function (AF) based on one or more predefined conditions comprise: when the UE (100) includes the unavailability period duration and does not include the start of unavailability period during the registration procedure or deregistration procedure; or when the unavailability period duration starts based on the start of unavailability period stored in a UE context at the network entity (200).

Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one ordinary skilled in the art to which this invention belongs. The system, methods, and examples provided herein are illustrative only and not intended to be limiting.

While specific language has been used to describe the present subject matter, any limitations arising on account thereto, are not intended. As would be apparent to a person in the art, various working modifications may be made to the method to implement the inventive concept as taught herein. The drawings and the forgoing description give examples of embodiments. Those skilled in the art will appreciate that one or more of the described elements may well be combined into a single functional element. Alternatively, certain elements may be split into multiple functional elements. Elements from one embodiment may be added to another embodiment.

The embodiments disclosed herein can be implemented using at least one hardware device and performing network management functions to control the elements.

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

The abbreviations and definitions mentioned in Table 1 may be used in the present disclosure:

Claims

A method performed by a user equipment (UE) in a wireless communication system, the method comprising:

transmitting, to an access and mobility management function (AMF) entity, a first message including information on an unavailability period for a non access stratum (NAS) signaling connection;

receiving, from the AMF entity, a second message;

starting a timer for releasing the NAS signaling connection; and

releasing the NAS signaling connection upon an expiry of the timer.
The method of claim 1,

wherein the timer is started based on the received second message.
The method of claim 1,

wherein the first message does not include information on a start of an unavailability period.
The method of claim 1,

wherein the first message is a registration request message, and

wherein the second message is a registration accept message.
A method performed by an access and mobility management function (AMF) entity in a wireless communication system, the method comprising:

receiving, from a user equipment (UE), a first message including information on an unavailability period for a non access stratum (NAS) signaling connection;

transmitting, to the UE, a second message; and

releasing the NAS signaling connection after the second message.
The method of claim 5,

wherein, in case that the first message includes information on a start of an unavailability period and the unavailability period starts, the method further comprising:

detecting a loss of connectivity event; and

transmitting, to an application function (AF) entity via a network exposure function (NEF) entity, a third message indicating the loss of connectivity event.
The method of claim 5,

wherein, in case that the first message does not include information on a start of an unavailability period, the method further comprising:

detecting a loss of connectivity event; and

transmitting, to an application function (AF) entity via a network exposure function (NEF) entity, a third message indicating the loss of connectivity event.
The method of claim 5,

wherein the first message is a registration request message, and

wherein the second message is a registration accept message.
A user equipment (UE) in a wireless communication system, the UE comprising:

a transceiver; and

a controller coupled with the transceiver and configured to:

transmit, to an access and mobility management function (AMF) entity, a first message including information on an unavailability period for a non access stratum (NAS) signaling connection;

receive, from the AMF entity, a second message;

start a timer for releasing the NAS signaling connection; and

release the NAS signaling connection upon an expiry of the timer.
The UE of claim 9,

wherein the timer is started based on the received second message.
The UE of claim 9,

wherein the first message does not include information on a start of an unavailability period.
The UE of claim 9,

wherein the first message is a registration request message, and

wherein the second message is a registration accept message.
An access and mobility management function (AMF) entity in a wireless communication system, the AMF entity comprising:

a transceiver; and

a controller coupled with the transceiver and configured to:

receive, from a user equipment (UE), a first message including information on an unavailability period duration for a non access stratum (NAS) signaling connection;

transmit, to the UE, a second message; and

release the NAS signaling connection after the second message.
The AMF entity of claim 13,

wherein, in case that the first message includes information on a start of an unavailability period and the unavailability period starts, the controller further configured to:

detect a loss of connectivity event; and

transmit, to an application function (AF) entity via a network exposure function (NEF) entity, a third message indicating the loss of connectivity event.
The AMF entity of claim 13,

wherein, in case that the first message does not include information on a start of an unavailability period, the controller further is configured to:

detect a loss of connectivity event; and

transmit, to an application function (AF) entity via a network exposure function (NEF) entity, a third message indicating the loss of connectivity event.