PLMN (Public Land Mobile Network) searching and selecting method and device after entry deletion in wireless network

Abstract

The present disclosure relates to a 5G or 6G communication system supporting a higher data transmission rate. The embodiment of the invention provides a PLMN (Public Land Mobile Network) searching and selecting method executed by UE (User Equipment) after a candidate PLMN is removed from a wireless network. The method comprises the following steps: determining that the UE is in a limited service state; further, the method comprises determining an entry to remove at least one candidate PLMN from a list of PLMNs that are not allowed to run at a current location of the UE; further, the method includes triggering PLMN selection if the entry is removed from the PLMN list and the UE is in a limited service state.

Description

Technical Field

[0001] The present disclosure relates to wireless networks, and more particularly to a method and user equipment (UE) for public land mobile network (PLMN) search and selection after entry deletion in a wireless network. Background Art

[0002] 5G mobile communication technology defines a wide frequency band, making it possible to achieve high transmission rates and new services. These technologies can be implemented not only in the "below 6GHz" frequency band such as 3.5GHz, but also in the "above 6GHz" frequency band called millimeter wave, including frequency bands such as 28GHz and 39GHz. In addition, in order to achieve a transmission rate fifty times faster than 5G mobile communication technology and ultra-low latency transmission that is only one-tenth of 5G mobile communication technology, 6G mobile communication technology (also called super 5G system) is being considered for implementation in the terahertz frequency band (for example, 95GHz to 3THz frequency band).

[0003] In the early stages of 5G mobile communication technology development, in order to support services and meet performance requirements related to enhanced mobile broadband (eMBB), ultra-reliable and low-latency communications (URLLC), and massive machine type communications (mMTC), the industry has been conducting standardization work in the following areas: standardization of beamforming and massive MIMO to mitigate radio wave path loss in millimeter waves and increase radio wave transmission distance; standardization of support parameter sets (e.g., operating multiple subcarrier spacings) to efficiently utilize millimeter wave resources and enable dynamic operation of time slot formats; standardization of initial access technology to support multi-beam transmission and wide bands; standardization of the definition and operation of bandwidth parts (BWPs); standardization of new channel coding methods, such as LDPC (low-density parity check) codes for large amounts of data transmission and polarization codes for highly reliable transmission of control information; standardization of L2 preprocessing; and standardization of network slicing to provide dedicated networks for specific services.

[0004] Currently, discussions on the improvement and performance enhancement of the first generation of 5G mobile communication technology are ongoing, given the services that 5G mobile communication technology is to support. Physical layer standardization is also advancing, involving technologies such as: V2X (Vehicle-to-Everything) technology, which uses the position and status information transmitted by the autonomous vehicle to assist in making driving decisions and improve the user experience; NR-U (New Radio Unlicensed) technology, which aims to make the system operation comply with various regulatory requirements in the unlicensed frequency band; NR UE energy saving technology; Non-Terrestrial Network (NTN) technology, which is a direct communication between the user equipment and the satellite to ensure coverage in areas where communication with the terrestrial network is not possible, and positioning technology.

[0005] In addition, standardization work has been ongoing for air interface architecture / protocols such as Industrial Internet of Things (IIoT) technologies that support interoperability and integration with other industries to provide new services, Integrated Access and Backhaul (IAB) technologies that provide nodes for network service area expansion by supporting wireless backhaul links and access links in an integrated manner, mobility enhancement technologies including conditional switching and dual active protocol stack (DAPS) switching, and two-step random access (i.e., NR's two-step random access channel RACH) for simplifying the random access process. In terms of system architecture / services, standardization work is also ongoing for 5G baseline architectures (e.g., service-based architectures or service-based interfaces) that combine network function virtualization (NFV) and software defined network (SDN) technologies, and mobile edge computing (MEC) that receives services based on UE location.

[0006] With the commercialization of 5G mobile communication systems, an exponentially growing number of connected devices will be connected to the communication network. Therefore, it is expected that the functions and performance of 5G mobile communication systems need to be enhanced and the integrated operation of connected devices can be realized. To this end, new research programs are being carried out, such as extended reality (XR) to effectively support applications such as augmented reality (AR), virtual reality (VR) and mixed reality (MR), using artificial intelligence (AI) and machine learning (ML) to achieve 5G performance improvement and complexity reduction, providing AI service support, supporting metaverse services, and drone communication services.

[0007] In addition, this development of 5G mobile communication systems will not only lay the foundation for the development of the following technologies: new waveforms that provide terahertz band coverage for 6G mobile communication technology, full-dimensional MIMO (FD-MIMO), multi-antenna transmission technologies such as array antennas and massive antennas, metamaterial-based lenses and antennas for improving the coverage of terahertz band signals, and high-dimensional spatial multiplexing technologies using OAM (orbital angular momentum) and RIS (reconfigurable smart surface); but will also lay the foundation for the development of the following technologies: full-duplex technology for improving the frequency efficiency of 6G mobile communication technology and improving system networks, AI-based communication technology that uses satellites and AI (artificial intelligence) to achieve system optimization from the design stage and internalizes end-to-end AI support functions to achieve system optimization, and next-generation distributed computing technology that uses ultra-high performance communication and computing resources to achieve complex-level services that exceed the limits of UE operating capabilities. Summary of the invention

[0008] Technical issues

[0009] The purpose of the present disclosure is to solve at least one of the deficiencies existing in the prior art.

[0010] In the 3GPP system, when the UE is in a restricted state, after removing or deleting the PLMN from the list of "PLMNs not allowed to operate at the current UE location", no action or behavior is further specified or defined for the MS or UE to handle the PLMN list. Therefore, it is urgent to define a method. It is expected that the method can solve the above-mentioned shortcomings or other deficiencies, or at least provide a useful alternative.

[0011] Solutions to technical problems

[0012] Therefore, an embodiment of the present disclosure provides a method for performing PLMN search and selection after removing a candidate PLMN in a wireless network, performed by a user equipment (UE). The method includes determining that the UE is in a limited service state. Further, the method also includes determining that at least one candidate PLMN entry is removed from a list of public land mobile networks (PLMNs) that are not allowed to operate at the current location of the UE. Further, the method also includes triggering PLMN selection when the entry is removed from the PLMN list and the UE is in a limited service state.

[0013] In one embodiment, the entry is removed from the PLMN list when the UE successfully registers to the PLMN stored in the entry via satellite Next Generation Radio Access Network (NG-RAN) access technology and the UE is not registering for emergency services.

[0014] In one embodiment, the entry is removed from the PLMN list upon expiration of a timer instance associated with the entry.

[0015] In one embodiment, the entry is removed from the PLMN list when the current UE location is known, the geographical location associated with the entry is stored in the UE and the distance between the geographical location and the current UE location is greater than a third value.

[0016] Correspondingly, the disclosed embodiment aims to provide a UE for searching and selecting a PLMN after removing a candidate PLMN in a wireless network. The UE includes a controller in communication connection with a communicator. The controller is configured to detect and determine that the UE is in a limited service state. Further, the controller is also configured to determine to remove at least one entry of a candidate PLMN from a list of public land mobile networks (PLMNs) that are not allowed to operate at the current location of the UE. Further, the controller is also configured to trigger a PLMN selection process when the entry is removed from the PLMN list and the UE is in a limited service state.

[0017] These and other aspects of the embodiments described in the present disclosure will be better understood in conjunction with the following description and accompanying drawings. However, it should be understood that the following description, although indicating preferred embodiments and numerous specific details thereof, is provided by way of example only and not limitation. Many changes and modifications may be made within the scope of the embodiments of the present disclosure without departing from the scope of the embodiments of the present disclosure, and the embodiments described in the present disclosure include all such modifications.

[0018] Beneficial Effects of the Invention

[0019] The main purpose of the embodiments of the present disclosure is to provide a method and UE for PLMN search and selection after removing candidate PLMNs in a wireless network.

[0020] Another object of the embodiments of the present disclosure is to provide a method: when an entry in the list is removed, if the UE is already in a normal service state and is receiving service from the PLMN, it is desired that the UE does not take any action.

[0021] Another object of the embodiments of the present disclosure is to provide a method: when an entry in the list is deleted and the UE is in a limited service state and does not obtain any service, the UE triggers the execution of PLMN selection.

[0022] Another object of the embodiments of the present disclosure is to provide a method: when the entry in the list is not deleted and the UE is in the limited service state and does not obtain any service, the UE will continue to remain in the limited service state.

[0023] Another object of an embodiment of the present disclosure is to provide a method, comprising: when a PLMN entry is deleted from the list and the UE is in a 5GMM-DEREGISTERED.LIMITED-SERVICE state, the UE will perform PLMN selection. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The method and UE described in the present disclosure are shown in the accompanying drawings, and similar reference numerals throughout the accompanying drawings represent corresponding parts in each figure. The embodiments of the present disclosure can be better understood from the following description in conjunction with the accompanying drawings, wherein:

[0025] Figure 1 A flow chart showing the interaction scenarios between multiple PLMNs and UEs;

[0026] Figure 2 Various hardware components of a UE according to an embodiment of the present disclosure are shown;

[0027] Figure 3 A flowchart of a PLMN search and selection method after removing a candidate PLMN in a wireless network according to an embodiment of the present disclosure is shown;

[0028] Figure 4 A flowchart of an interaction scenario between multiple PLMNs and UEs proposed according to an embodiment of the present disclosure is shown;

[0029] Figure 5 A flow chart of another interaction scenario between multiple PLMNs and UE according to an embodiment of the present disclosure is shown.

[0030] It is worth noting that, where possible, the same reference numerals have been used to represent the same elements in the drawings. In addition, it should be understood by those skilled in the art that the elements in the drawings are drawn for simplicity and may not be presented strictly to scale. For example, the dimensions of certain elements in the drawings may be exaggerated relative to other elements to better assist in understanding various aspects of the present disclosure. In addition, one or more elements may have been represented in the drawings using conventional symbols, and the drawings may only show specific details relevant to understanding the embodiments of the present disclosure, so as to avoid obscuring the drawings by details that are obvious to those skilled in the art. DETAILED DESCRIPTION

[0031] The embodiments in the present disclosure and their various features and beneficial details will be explained more fully in conjunction with the non-limiting embodiments shown in the accompanying drawings and the following detailed description. In order not to cause unnecessary ambiguity in the embodiments of the present disclosure, the description of well-known components and processing technologies is omitted. In addition, the various embodiments described in the present disclosure are not necessarily mutually exclusive, because some embodiments can be combined with one or more other embodiments to form new embodiments. Unless otherwise stated, the word "or" used in the present disclosure is non-exclusive. The examples used in the present disclosure are only intended to facilitate the understanding of the practical methods of the embodiments and to further enable those skilled in the art to implement the embodiments in the present disclosure. Therefore, the examples should not be interpreted as limiting the scope of the embodiments of the present disclosure.

[0032] In the art, as a rule, embodiments may be described and illustrated in terms of modules that perform the functions. These modules may be referred to as managers, units, modules, hardware components, etc. in the present disclosure, which 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, hard-wired circuits, etc.), and may be selectively driven by firmware and software. For example, these circuits may be embodied on one or more semiconductor chips, or on substrate supports such as printed circuit boards. The circuits constituting a module may be implemented by dedicated hardware, or by a processor (e.g., one or more programmed microprocessors and associated circuits), or by a combination of dedicated hardware for executing some functions of the module and a processor for executing other functions of the module. Without exceeding the scope of the present disclosure, each module in the embodiment may be physically separated into two or more interacting and separate modules. Similarly, the modules in the embodiment may also be physically combined into more complex modules without exceeding the scope of the present disclosure.

[0033] Therefore, an embodiment of the present disclosure is intended to provide a PLMN search and selection method after removing a candidate PLMN in a wireless network.

[0034] In an embodiment, when a timer instance associated with any one or more entries expires, or, if the current UE location is known, the geographical location associated with any one or more PLMN entries has been stored and the distance from the current UE location is greater than a UE implementation specific value for any one or more PLMNs, then in the proposed method, when the UE is in limited service state, PLMN search and PLMN selection are triggered. In another embodiment, when the UE is in normal service state, triggering PLMN search and PLMN selection is avoided. In another alternative embodiment, when the UE is in normal service state, triggering PLMN search and PLMN selection is considered.

[0035] Now referring to the drawings, in particular, Figures 1 to 5 , showing a preferred embodiment, like reference characters in the figures consistently denote corresponding features throughout the drawings.

[0036] For the 3rd Generation Partnership Project (3GPP) satellite Next Generation Radio Access Network (NG-RAN), the UE stores a list of PLMNs that are not allowed to operate at the current UE location. Each entry contains the following information:

[0037] a) the PLMN identity (ID) of the PLMN that sent the message including the fifth generation non-access stratum (5G NAS) mobility management (5GMM) cause value #78 “PLMN not allowed to operate at the current UE location” over the satellite NG-RAN access technology;

[0038] b) the geographical location (if known by the UE) at which 5GMM cause value #78 was received over the satellite NG-RAN access technology;

[0039] c) The UE implementation specific distance value (if the geographical location exists) should not be set to a value less than the value indicated by the wireless network (if any).

[0040] Before storing a new entry in the list, the UE deletes any existing entry with the same PLMN identity. After storing the new entry, the UE starts a timer instance associated with the entry based on an implementation specific value, which shall not be set to a value less than the timer value indicated by the radio network. The UE is only allowed to attempt to access a PLMN that is part of the list of "PLMNs not allowed to operate in the current UE location" via satellite NG-RAN access technology if:

[0041] a) the current UE location is known, the geographical location associated with the PLMN entry is stored and the distance to the current UE location is greater than a UE implementation specific value. The UE implementation specific value shall not be set to a value less than the value indicated by the network;

[0042] b) the timer associated with the PLMN entry expires; or

[0043] c) The visit is for emergency services.

[0044] The list can contain three or more entries. The maximum number of entries is implementation-determined. When the list is full and a new entry needs to be inserted, the oldest entry is removed. For each entry, it is removed if the following conditions are met:

[0045] a) the UE successfully registers to the PLMN stored in this entry via satellite NG-RAN access technology; or

[0046] b) The timer instance associated with the entry expires.

[0047] If the current UE location is known and the geographical location associated with the PLMN entry is stored and the distance to the current UE location is greater than a UE implementation specific value, the UE may delete the entry from the list. When the UE is switched off, the UE saves the list of "PLMNs not allowed to operate at the current UE location" in its non-volatile memory. If the Universal Subscriber Identity Module (USIM) is removed, the UE shall delete the list of "PLMNs not allowed to operate at the current UE location".

[0048] In order to obtain services on the PLMN through satellite NG-RAN access technology, the UE or mobile station (MS) attempts to find a suitable cell in the PLMN through the PLMN search process. When the UE or MS finds a suitable cell in the PLMN, the UE attempts to register on the PLMN. If the registration is successful, the UE will camp on the suitable cell. Otherwise, the UE will try the next PLMN. If all registration attempts for PLMNs fail, the UE will enter the limited service state. In the limited service state, the UE can only make emergency calls or receive Earthquake and Tsunami Warning System (ETWS) messages. If the registration attempt on any PLMN is successful, the UE enters the normal service state. When the UE or MS receives an integrity protection rejection message for a PLMN from a satellite NG-RAN cell and the message has a cause value #78 "PLMN not allowed to operate at the current UE location", the UE or MS maintains a list of "PLMNs not allowed to operate at the current UE location". Now, for one or more PLMNs in the "PLMNs not allowed to operate at the current UE location" list, if the timer instance associated with the entry expires, or if the current UE location is known, the geographical location related to the PLMN entry has been stored and the distance from the current UE location is greater than the UE implementation specific value, then the PLMN entry will be removed / deleted from the "PLMNs not allowed to operate at the current UE location" list.

[0049] Regarding the handling of the PLMN list after the PLMN is removed / deleted from the "PLMNs not allowed to operate at the current UE location" list after the timer instance associated with the entry expires, or the current UE location is known, the geographical location associated with the PLMN entry is stored and the distance to the current UE location is greater than the UE implementation specific value, and the UE is in a restricted state or normal service state, there is no further specification or definition in the 3GPP system regarding the actions or behaviors that the MS or UE should take. Therefore, a method needs to be defined in the 3GPP system.

[0050] Figure 1A flow chart (S100) of the interaction scenario between multiple PLMNs and UE is shown. In step S102, there are a first PLMN, a second PLMN and a third PLMN available for use in the area. In step S104a, since the UE previously received an integrity protection rejection message with a cause value #78 for these PLMNs, the first PLMN, the second PLMN and the third PLMN are all included in the list of "PLMNs not allowed to operate at the current UE location".

[0051] In step S106a, since there is no available PLMN to camp on, the UE enters a limited service state after attempting to register. In step S108a, when a timer instance associated with any entry expires, or if the current UE location is known, the geographical location associated with the PLMN entry has been stored and the distance to the current UE location is greater than a UE implementation specific value for any PLMN (e.g., the first PLMN), the entry is removed / deleted from the list and the PLMN will be available for the PLMN search or PLMN selection process.

[0052] Alternatively, in step S102, the first PLMN, the second PLMN and the third PLMN are all available in the area. In step S104b, since the UE previously received an integrity protection rejection message with a cause value #78 regarding these PLMNs, the first PLMN and the second PLMN are included in the list of "PLMNs not allowed to operate at the current UE location".

[0053] In step S106b, since the third PLMN is available for camping, the UE camps on the third PLMN after attempting to register and enters the normal service state. In step S108b, when the timer instance associated with any entry expires, or, if the current UE location is known, the geographical location associated with the PLMN entry is stored and the distance from the current UE location is greater than a UE implementation specific value for any PLMN (e.g., the first PLMN), the entry is removed / deleted from the list and the PLMN will be available for PLMN search or PLMN selection process.

[0054] In step S110, for the handling of the MS or UE in terms of the PLMN list after the PLMN is removed / deleted from the list of "PLMNs not allowed to operate at the current UE location" when the UE is in normal service state, no further operation or behavior is specified or defined in the 3GPP system. Therefore, a method needs to be defined in the 3GPP system.

[0055] Figure 2Various hardware components of a UE (100) according to an embodiment of the present disclosure are shown. The UE (100) may be, but is not limited to, a laptop, a smartphone, a desktop computer, a notebook, a device-to-device (D2D) device, a vehicle-to-everything (V2X) device, a foldable phone, a smart TV, a tablet computer, an immersive device, and an Internet of Things (IoT) device. In one embodiment, the UE (100) includes a processor (110), a communicator (120), a memory (130), and a PLMN removal controller (140). The processor (110) is connected to the communicator (120), the memory (130), and the PLMN removal controller (140).

[0056] The PLMN removal controller (140) detects that an entry of a candidate PLMN is removed from a list of PLMNs that are not allowed to operate at the current location of the UE (100). In another embodiment, when the current location of the UE (100) is known, a geographical location associated with the candidate PLMN entry is stored and a distance from the current location of the UE (100) is greater than a UE implementation specific value, the candidate PLMN is removed from the list of PLMNs that are not allowed to operate at the current location of the UE (100).

[0057] In one embodiment, the PLMN removal controller (140) determines whether one of the following two conditions is true: "the UE (100) successfully registers to the PLMN stored in the entry via the satellite NG-RAN access technology, except when the UE (100) registers for emergency services" and "the timer instance associated with the entry expires". Further, when one of the two conditions of the UE (100) successfully registering and the timer instance associated with the entry expires, the PLMN removal controller (140) removes the entry of the candidate PLMN from the list of PLMNs that are not allowed to operate at the current location of the UE (100).

[0058] In addition, the PLMN removal controller (140) determines whether the UE (100) is in a limited service state or a normal service state. In one embodiment, when it is determined that the candidate PLMN is removed when the UE (100) is in a limited service state, the PLMN removal controller (140) triggers one of a PLMN search or a PLMN selection. In another embodiment, when it is determined that the candidate PLMN is removed when the UE (100) is in a normal service state, the PLMN removal controller (140) avoids triggering one of a PLMN search or a PLMN selection.

[0059] The PLMN removal controller (140) is implemented by analog and / or digital circuits, such as logic gates, integrated circuits, microprocessors, microcontrollers, memory circuits, passive electronic components, active electronic components, optical components, hard-wired circuits, etc., and can optionally be driven by firmware.

[0060] In addition, the processor (110) is configured to execute instructions stored in the memory (130) and perform various processes. The communicator (120) is configured to communicate internally between internal hardware components and to communicate with external devices via one or more networks. The memory (130) stores instructions to be executed by the processor (110). The memory (130) may include non-volatile storage elements. Examples of these non-volatile storage elements may include magnetic hard disks, optical disks, floppy disks, flash memory, or electrically programmable memory (EPROM) or electrically erasable programmable (EEPROM) memory. In addition, in some examples, the memory (130) may be considered a non-transitory storage medium. The term "non-transitory" indicates that the storage medium is not embodied in the form of a carrier or propagating signal. However, the term "non-transitory" should not be interpreted as the memory (130) being non-removable. In some examples, a non-transitory storage medium may store data that changes over time (e.g., in a random access memory (RAM) or cache).

[0061] although Figure 2 Various hardware components of the UE (100) are shown, but it should be understood that other embodiments are not limited thereto. In other embodiments, the UE (100) may include fewer or more components. In addition, the labels or names of the components are for illustrative purposes only and do not limit the scope of the present invention. One or more components may be combined to perform the same or substantially similar functions in the UE (100).

[0062] Figure 3 A flowchart (S300) of a PLMN search and selection method after a candidate PLMN is removed in a wireless network (not shown) according to an embodiment of the present disclosure is shown. The wireless network may be, but is not limited to, for example, a fourth generation (4G) network, a fifth generation (5G) network, and an open radio access network (ORAN). Operations (S302-S308) are processed by a PLMN removal controller (140).

[0063] In step S302, the method includes detecting that an entry of a candidate PLMN in a list of PLMNs that are not allowed to operate at a current location of the UE (100) has been removed. In step S304, the method includes determining whether the UE (100) is in a limited service state or a normal service state. In step S306, the method includes triggering one of a PLMN search and a PLMN selection when it is determined that the candidate PLMN is removed when the UE (100) is in the limited service state. In step S308, the method includes avoiding triggering one of a PLMN search and a PLMN selection when it is determined that the candidate PLMN is removed when the UE (100) is in the normal service state.

[0064] Figure 4 A flow chart (S400) of an interaction scenario between multiple PLMNs and a UE (100) according to an embodiment of the present disclosure is shown.

[0065] In step S402, the first PLMN, the second PLMN and the third PLMN are all available in the area, and the UE (100) has tried all of these PLMNs, but the UE (100) or the MS receives an integrity protection reject message with a cause value of #78 "PLMN not allowed to operate at the current UE location" for all of these PLMNs from the satellite NG-RAN cell.

[0066] In step S404, the UE (100) or MS enters a limited service state (i.e., one of 5GMM-REGISTERED.LIMITED-SERVICE or 5GMM-DEREGISTERED.LIMITED-SERVICE), or may enter any state in which the UE will not obtain any service. In step S406, a timer instance associated with any entry expires, or, if the current UE location is known, a geographic location associated with the PLMN entry has been stored and the distance to the current UE location is greater than a UE implementation specific value for any PLMN (e.g., the first PLMN).

[0067] In step S408, typically, for any reason, the first PLMN is removed or deleted from the list of "PLMNs not allowed to operate at the current UE location", or the entire list is deleted, and then the first PLMN is available for the PLMN search or PLMN selection process.

[0068] In step S410, the UE (100) now regards the first PLMN as an available PLMN and triggers PLMN search and PLMN selection, or attempts to perform PLMN search and PLMN selection on the PLMN. That is, the UE (100) performs cell selection (i.e., on 3GPP access) or cell reselection according to 3GPP TS 38.304 or 3GPP TS 36.304, or performs PLMN selection according to the procedure defined in 3GPP TS 23.122.

[0069] Figure 5 Another interaction flow chart ( S500 ) between multiple PLMNs and UE ( 100 ) according to an embodiment of the present disclosure is shown.

[0070] In step S502, it is assumed that the first PLMN, the second PLMN and the third PLMN are available PLMNs in the area, and the UE (100) has attempted to access all of these PLMNs, but the UE (100) or the mobile station (MS) receives an integrity protection rejection message with a cause value of #78 "PLMNs not allowed to operate at the current UE location" for the first PLMN and the second PLMN from the satellite NG-RAN cell. The two PLMNs are added to the "PLMNs not allowed to operate at the current UE location" list together with the UE's geographic location and the UE-implemented specific distance value. In addition, the UE (100) starts corresponding timer instances for the two PLMNs.

[0071] In step S504, the UE (100) or MS attempts to register on the third PLMN and successfully registers on the third PLMN, and transfers from the PLMN search state (i.e., usually not the limited service state) to the normal service state (i.e., 5GMM registration-normal service).

[0072] In step S506, the UE (100) detects that a timer instance associated with any one of the entries has expired, or, if the current UE location is known, detects that a geographical location associated with the PLMN entry has been stored and the distance from the current UE location is greater than a UE implementation specific value for any one of the PLMNs (e.g., the first PLMN) in the list.

[0073] In step S508, typically, for any reason, the first PLMN is removed or deleted from the list of "PLMNs not allowed to operate at the current UE location", or the entire list of "PLMNs not allowed to operate at the current UE location" is deleted.

[0074] In step S510, now, since the UE (100) has been registered on the third PLMN, the UE (100) does not consider triggering PLMN search and PLMN selection on the first PLMN, nor does it attempt to perform PLMN search and PLMN selection on the first PLMN.

[0075] In another embodiment, the UE (100) considers the first PLMN as an available PLMN and triggers PLMN search and PLMN selection, or attempts to perform PLMN search and PLMN selection on the PLMN. That is, the UE (100) performs cell selection (i.e., on 3GPP access) or cell reselection according to 3GPP TS38.304 or 3GPP TS 36.304, or performs the PLMN selection process defined in 3GPP TS23.122.

[0076] In yet another embodiment, if the UE (100) determines that the UE (100) is in a discontinuous coverage area (DC), the UE (100) is in a "no available cell" or PLMN search substate, and a timer instance associated with any one of the entries expires, or, if the current UE location is known, the geographic location associated with the PLMN entry has been stored and the distance to the current UE location is greater than a UE implementation specific value for any one of the PLMNs in the "PLMNs not allowed to operate at the current UE location" list, then the UE (100) will avoid triggering PLMN search and PLMN selection.

[0077] In another embodiment, if the UE (100) determines that it is in a discontinuous coverage area, it is not in the "no available cell" state or the PLMN search substate, and the timer instance associated with any entry expires, or, if the current UE location is known, the geographical location associated with the PLMN entry has been stored and the distance to the current UE location is greater than a UE implementation specific value for any PLMN in the "PLMNs not allowed to operate at the current UE location" list, then the UE (100) may or may not trigger a PLMN search and PLMN selection.

[0078] In embodiments, the words "remove" and "delete" are used interchangeably and refer to the same event in this disclosure.

[0079] The UE (100) / network may select one or more of the solutions in any random order.

[0080] Although the problems / solutions proposed in the embodiments are explained with satellite NG-RAN access technology, the solutions proposed in the embodiments are also applicable to satellite E-UTRAN access technology, NB (narrowband)-S1 mode or broadband (WB). The problems / solutions proposed in the embodiments are also applicable to any type of service, such as normal service, emergency service, SNPN, NPN, e-NPN, LADN, MEC, etc., as well as broadband-S1 mode implemented by satellite E-UTRAN access and / or NB-IoT (narrowband Internet of Things) or WB-IoT (broadband Internet of Things) satellite access / architecture.

[0081] The problem / solution proposed in this embodiment is also applicable to various services, such as normal services, emergency services, SNPN, NPN, e-NPN, LADN, MEC, etc.

[0082] Although the network used in the embodiment is explained using any 5G core network function taking the access and mobility management function (AMF) as an example, the network may also be any fifth generation (5G) / evolved universal mobile telecommunications access network (EUTRAN) core network entity, such as AMF / session management function (SMF) / mobility management entity (MME) / user plane function (UPF), or the network may also be any 5G / EUTRAN radio access network entity, such as eNodeB (eNB) or gNodeB (gNB) or NG-RAN, etc.

[0083] In the embodiments, NR satellite access network, satellite access network and satellite NG-RAN access technology may be used interchangeably and have the same meaning.

[0084] The various actions, behaviors, modules, steps, etc. (S100, S300-S500) in the flow chart can be performed in the order presented, in different orders, or simultaneously. In addition, in some embodiments, certain actions, behaviors, modules, steps, etc. may be omitted, added, modified, and skipped without exceeding the scope of the present invention.

[0085] The above description of the specific embodiments will fully reveal the general nature of the embodiments of the present disclosure, so that others can easily modify and / or adjust these specific embodiments to adapt to various applications by applying existing knowledge without departing from the basic concepts. Therefore, such adjustments and modifications should also be understood to be within the meaning and scope of the equivalent embodiments of the disclosed embodiments, and should also be included therein. It should be understood that the wording or terminology used in the present disclosure is for descriptive purposes, not for limitation. Therefore, although the embodiments of the present disclosure have been described in the form of preferred embodiments, those skilled in the art should understand that these embodiments can be practiced by modifications within the scope of the embodiments described in the present disclosure.

Claims

1. A method performed by a user equipment (UE) in a non-terrestrial network, the UE comprising: Determining whether the UE is in a limited service state; determining whether a PLMN entry is removed from a list of public land mobile networks PLMNs that are not allowed to operate in the current location of the UE; as well as In case the entry is removed from the PLMN list and the UE is in a limited service state, PLMN selection is performed.

2. The method according to claim 1, further comprising: When the UE successfully registers to the PLMN stored in the entry through a satellite next generation radio access network NG-RAN access technology and the UE is not registered for emergency services, the entry is removed from the PLMN list.

3. The method according to claim 1, further comprising: Upon expiration of a timer instance associated with the entry, the entry is removed from the PLMN list.

4. The method according to claim 3, wherein: The timer instance is set to a first value that is not less than a second value indicated by the network.

5. The method according to claim 1, further comprising: In a case where the current UE location is known, the UE stores a geographical location associated with the entry, and the distance between the geographical location and the current UE location is greater than a third value, the entry is removed from the PLMN list.

6. The method according to claim 1, wherein: In case the UE is switched off, the PLMN list is stored in a non-volatile memory of the UE.

7. The method according to claim 1, wherein: In case a universal subscriber identity module (USIM) is removed from the UE, the PLMN list is deleted from the UE.

8. A user equipment UE in a non-terrestrial network, the UE comprising: communicator; as well as The controller is configured as: Determining whether the UE is in a limited service state; determining whether a PLMN entry is removed from a list of public land mobile networks PLMNs that are not allowed to operate in a current location of the UE; as well as In case the entry is removed and the UE is in a limited service state, PLMN selection is performed.

9. The UE according to claim 8, wherein: The controller is further configured to: In a case where the UE successfully registers to the PLMN stored in the entry through a satellite next generation radio access network NG-RAN access technology and the UE is not registered for emergency services, the entry is removed from the PLMN list.

10. The UE according to claim 8, wherein: The controller is further configured to: Upon expiration of a timer instance associated with the entry, the entry is removed from the PLMN list.

11. The UE according to claim 10, wherein: The timer instance is set to a first value that is not less than a second value indicated by the network.

12. The UE according to claim 8, wherein: The controller is further configured to: In a case where the current UE location is known, the UE stores a geographical location associated with the entry, and the distance between the geographical location and the current UE location is greater than a third value, the entry is removed from the PLMN list.

13. The UE according to claim 8, wherein: In case the UE is switched off, the PLMN list is stored in a non-volatile memory of the UE.

14. The UE according to claim 8, wherein: In case that a universal subscriber identity module (USIM) is removed from the UE, the PLMN list is deleted from the UE.

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