Method and apparatus for managing equivalent PLMN lists to enhance disaster roaming service in wireless communication network system

Abstract

The present invention provides a method for managing Equivalent Public Land Mobile Networks (EPLMN) list for disaster roaming services in a wireless communication network system. The method includes determining, by a User Equipment (UE) (101), that a disaster condition has occurred and no other PLMNs are available except for PLMNs in a forbidden PLMN list or allowable PLMNs unable to provide the EPS services or 5GS services. Further, the method includes transmitting, by the UE (101), a Non-Access Stratum (NAS) request message to a first PLMN. Further, the method includes　receiving, by the UE (101), a NAS accept message from the first PLMN. Further, the method includes storing, by the UE (101), the Equivalent PLMNs received from the first PLMN as a "list of equivalent PLMNs". The UE (101) does not remove PLMNs from the list of equivalent PLMNs even when they are available in the list of forbidden PLMNs in the UE (101).

Description

METHOD AND APPARATUS FOR MANAGING EQUIVALENT PLMN LISTS TO ENHANCE DISASTER ROAMING SERVICE IN WIRELESS COMMUNICATION NETWORK SYSTEM

[0001] The present invention pertains to a wireless communication network system, and more specifically, to a method and system for managing an equivalent Public Land Mobile Network (PLMN) list to enhance disaster roaming services within a wireless communication network system.

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

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

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

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

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

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

[0008] The principal object of the invention herein is to manage Equivalent PLMN List for Disaster Roaming Services in wireless communication network system (in the 5GS and EPS).

[0009] Yet another object of the invention is to provide a method and system for enabling a UE to retain forbidden PLMNs in an Equivalent PLMN (EPLMN) list during disaster roaming conditions, thereby ensuring continuous network connectivity and service availability throughout ongoing disaster scenarios over the current PLMN and its equivalent PLMNs.

[0010] Yet another object of the invention is to prevent the deletion of disaster-capable PLMNs from the EPLMN list upon release of emergency Protocol Data Unit (PDU) sessions or Packet Data Network (PDN) connections, thereby maintaining the UE's ability to perform cell reselection and mobility procedures among multiple disaster-capable networks.

[0011] Yet another objective of the present invention is to provide a mechanism for differentiating between normal registration procedures and disaster roaming registration procedures, enabling the UE to apply appropriate handling of the EPLMN list based on the registration context, thereby preserving network-provided disaster roaming capabilities.

[0012] Yet another objective of the present invention is to ensure seamless mobility and service continuity for disaster inbound roamers across multiple forbidden PLMNs designated as equivalent PLMNs for disaster roaming purposes, thereby enhancing the effectiveness of Multi-operator IP-based Network for Disaster Relief (MINT) services in emergency situations.

[0013] The technical subjects pursued in the disclosure may not be limited to the above-mentioned technical subjects, and other technical subjects which are not mentioned may be clearly understood, through the following descriptions, by those skilled in the art to which the disclosure pertains.

[0014] In an aspect, the objectives are achieved by providing a method for managing EPLMN list for disaster roaming services in a wireless communication network system. Further, the method includes determining by a UE that a disaster condition has occurred and no other PLMNs are available except for PLMNs in a forbidden PLMN list or allowable PLMNs unable to provide the EPS services or 5G system(5GS); services. Further, the method includes transmitting by the UE a Non-Access Stratum (NAS) request message to a first PLMN. The NAS request message includes a registration type value indicating disaster roaming initial registration or disaster roaming mobility registration update or attach type value indicating disaster roaming attach or EPS update type value indicating disaster roaming update. Further, the method includes receiving by the UE a NAS accept message from the first PLMN. The NAS accept message includes the equivalent PLMNs IE (information elements) having equivalent PLMNs capable of providing disaster roaming services. Further, the method includes storing by the UE the Equivalent PLMNs received from the first PLMN as a "list of equivalent PLMNs." The UE does not remove PLMNs from the list of equivalent PLMNs even when the PLMNs are available in the list of forbidden PLMNs in the UE.

[0015] In another aspect, the objectives are achieved by providing a user equipment for managing Equivalent Public Land Mobile Networks (PLMN) list for disaster roaming services in a wireless communication network system. Further, the UE includes a memory, a processor, and an EPLMN list controller. Further, the EPLMN list controller is coupled to the memory and the processor. The disaster roaming network selection controller determines that the disaster condition has occurred and no other PLMNs are available except for PLMNs in a forbidden PLMN list or PLMNs unable to provide the EPS services or 5G system (5GS); services. Further, the disaster roaming network selection controller transmits the Non-Access Stratum (NAS) request message to a first PLMN. The NAS request message includes the registration type value indicating disaster roaming initial registration or disaster roaming mobility registration update or attach type value indicating disaster roaming attach or EPS update type value indicating disaster roaming update. Further, the disaster roaming network selection controller receives the NAS accept message from the first PLMN. The NAS accept message includes the equivalent PLMNs IE (information elements) having equivalent PLMNs capable of providing disaster roaming services. Further, the disaster roaming network selection controller stores the Equivalent PLMNs received from the first PLMN as a "list of equivalent PLMNs." The UE does not remove PLMNs from the list of equivalent PLMNs even when the PLMN is available in the list of forbidden PLMNs in the UE.

[0016] These and other aspects of the embodiments herein will be better appreciated and understood when considered in conjunction with the following description and the accompanying drawings. It should be understood, however, that the following descriptions, while indicating preferred embodiments and numerous specific details thereof, are given by way of illustration and not of limitation. Many changes and modifications may be made within the scope of the embodiments herein, and the embodiments herein include all such modifications.

[0017] An embodiment of the disclosure provides method and apparatus to manage Equivalent PLMN List for Disaster Roaming Services in wireless communication network system (in the 5GS and EPS).

[0018] An embodiment of the disclosure provides a method and system for enabling a UE to retain forbidden PLMNs in an Equivalent PLMN (EPLMN) list during disaster roaming conditions, thereby ensuring continuous network connectivity and service availability throughout ongoing disaster scenarios over the current PLMN and its equivalent PLMNs.

[0019] An embodiment of the disclosure provides method and apparatus to prevent the deletion of disaster-capable PLMNs from the EPLMN list upon release of emergency Protocol Data Unit (PDU) sessions or Packet Data Network (PDN) connections, thereby maintaining the UE's ability to perform cell reselection and mobility procedures among multiple disaster-capable networks.

[0020] An embodiment of the disclosure provides method and apparatus to provide a mechanism for differentiating between normal registration procedures and disaster roaming registration procedures, enabling the UE to apply appropriate handling of the EPLMN list based on the registration context, thereby preserving network-provided disaster roaming capabilities.

[0021] An embodiment of the disclosure provides method and apparatus to ensure seamless mobility and service continuity for disaster inbound roamers across multiple forbidden PLMNs designated as equivalent PLMNs for disaster roaming purposes, thereby enhancing the effectiveness of Multi-operator IP-based Network for Disaster Relief (MINT) services in emergency situations.

[0022] Advantageous effects obtainable from the disclosure may not be limited to the above - mentioned effects, and other effects which are not mentioned may be clearly understood from the following descriptions by those skilled in the art to which the disclosure pertains.

[0023] These and other features, aspects, and advantages of the present invention are illustrated in the accompanying drawings, throughout which like reference letters indicate corresponding parts in the various figures. The embodiments herein will be better understood from the following description with reference to the drawings, in which:

[0024] FIG. 1 is a sequence diagram illustrating a process of the UE deleting FPLMN-B from an EPLMN list according to prior art.

[0025] FIG. 2 is a sequence diagram that illustrates a process of the UE obtaining disaster roaming services from the PLMNs included in the FPLMN list during the disaster condition according to prior art.

[0026] FIG. 3 is a block diagram that illustrates the UE for managing EPLMN list for disaster roaming services in a wireless communication network system according to embodiments as disclosed herein.

[0027] FIG. 4 is a flow chart that illustrates a method for managing the EPLMN list for disaster roaming services in a wireless communication network system according to embodiments as disclosed herein.

[0028] FIG. 5 is a sequence diagram that illustrates a process for the UE to retain all PLMNs in the EPLMN list including PLMNs from the forbidden PLMN list of the UE according to embodiments as disclosed herein.

[0029] FIG. 6 is a sequence diagram that illustrates a process for retaining PLMNs in the equivalent PLMN list during disaster roaming in a 5G system according to embodiments as disclosed herein.

[0030] FIG. 7 is a sequence diagram that illustrates a process for retaining PLMNs in the equivalent PLMN list during disaster roaming in an Evolved Packet System (EPS) according to embodiments as disclosed herein.

[0031] FIG. 8 is a block diagram of a base station (BS) 800 according to an embodiment of the disclosure.

[0032] FIG. 9 is a block diagram of a network entity 900 according to an embodiment of the disclosure.

[0033] 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 are not be construed as limiting the scope of the embodiments herein.

[0034] As is traditional in the field, embodiments are described and illustrated in terms of blocks that carry out a described function or functions.　These blocks, which referred to herein as managers, units, modules, hardware components or the like, are physically implemented by analog and / or digital circuits such as logic gates, integrated circuits, microprocessors, microcontrollers, memory circuits, passive electronic components, active electronic components, optical components, hardwired circuits and the like, and optionally be driven by firmware and software. The circuits, for example, be embodied in one or more semiconductor chips, or on substrate supports such as printed circuit boards and the like.　The circuits constituting a block be implemented by dedicated hardware, or by a processor (e.g., one or more programmed microprocessors and associated circuitry), or by a combination of dedicated hardware to perform some functions of the block and a processor to perform other functions of the block. Each block of the embodiments be physically separated into two or more interacting and discrete blocks without departing from the scope of the proposed method.　Likewise, the blocks of the embodiments be physically combined into more complex blocks without departing from the scope of the proposed method.

[0035] The accompanying drawings facilitate understanding of various technical features. The embodiments are not limited by these drawings and extend to any alterations, equivalents, and substitutes. Terms like first, second, etc., are used for distinction and do not limit the elements.

[0036] In recent years, the importance of reliable communication for User Equipment (UE) has become increasingly evident, particularly in the context of natural disasters and other emergencies. During such critical events, maintaining connectivity is essential for coordinating rescue operations, disseminating information, and ensuring public safety. wireless communication network systems, particularly those governed by the 3rd Generation Partnership Project (3GPP), play a pivotal role in facilitating such connectivity.

[0037] One significant advancement aimed at enhancing service reliability during disaster scenarios is the Minimization of Service Interruption (MINT) feature. The MINT feature enables the UE to obtain service from PLMNs that provide disaster roaming services upon detection of a disaster condition. The MINT feature is intended to ensure that communication services remain available even when primary network infrastructure is compromised.

[0038] However, the implementation of the MINT feature and disaster roaming services is associated with several challenges and limitations. A primary limitation is that the UE can obtain service under a disaster condition only if there are PLMN operators prepared to provide disaster roaming services. The minimization of service interruption is therefore constrained to specific times and locations, which may not correspond with the actual needs of affected users.

[0039] Another limitation arises from the potential congestion in the 5th Generation (5G) System and the Evolved Packet System (EPS) due to support for Disaster Roaming. The influx and outflux of Disaster Inbound Roamers may result in network overload, leading to degraded service quality, which is particularly problematic during emergencies when reliable communication is most critical.

[0040] Further, when the UE lacks coverage of its Home Public Land Mobile Network (HPLMN) and detects that a disaster condition applies to the HPLMN, the UE may register with a PLMN offering disaster roaming services. However, the 3GPP system requires mechanisms for PLMN operators to identify areas in which disaster conditions are applicable. The accurate and efficient dissemination of disaster information is difficult to achieve in rapidly evolving emergency scenarios.

[0041] The 3GPP further requires mechanisms for provision of service to Disaster Inbound Roamers only within regions in which disaster conditions apply. Additionally, the 3GPP system requires mechanisms for informing Disaster Inbound Roamers when a disaster condition ceases to apply. The absence of robust mechanisms for tracking and communicating disaster conditions in real-time constitutes a further limitation.

[0042] Additionally, the 3GPP system requires means for enabling the UE to access PLMNs included in a Forbidden PLMN (FPLMN) list when a disaster condition applies and no other PLMN is available. Implementation of such access introduces challenges related to security, authorization, and network interoperability, thereby creating further limitations in ensuring seamless and secure communication.

[0043] Further, the 3GPP system requires mechanisms for accurately managing charging information for Disaster Inbound Roamers, including information regarding applied disaster conditions. The absence of precise billing mechanisms may result in inaccurate or non-transparent charging for services provided during disaster scenarios, thereby constituting another limitation.

[0044] The MINT feature and disaster roaming capabilities provide significant potential for enhancing communication reliability during emergencies. However, these capabilities are constrained by limitations related to network congestion, real-time dissemination of disaster information, service provision restrictions, security and authorization challenges, network interoperability, and accurate charging of Disaster Inbound Roamers.

[0045] Thus, it is desired to address the above-mentioned disadvantages, issues, or other shortcomings, or at least provide a useful alternative.

[0046] FIG. 1 is a sequence diagram illustrating a process where UE deletes Forbidden Public Land Mobile Network-B (FPLMN-B) from an EPLMN list, , according to prior art. The scenario disclosed in FIG. 1 shows the UE (101) unable to acquire service due to the prior deletion of a PLMN from the EPLMN list during a Disaster Condition. A disaster condition refers to a situation determined and initiated by a government, typically in response to a natural disaster, and terminated by the government. When such a condition applies, the UE (101) can mitigate service interruptions and failures.

[0047] In one embodiment, the precondition establishes that the UE (101) shall avail MINT service only when a disaster condition has occurred, and no other PLMN is available except for those in the forbidden PLMN list of the UE (101) or allowable PLMNs unable to provide the EPS services or 5GS services. This precondition ensures that disaster roaming services are initiated exclusively during genuine disaster scenarios. The term Minimization of Service Interruption (MINT) refers to a feature enabling the UE (101) to obtain service from the PLMN providing disaster roaming when the disaster condition applies to the UE(s) (101) determined PLMN associated with the disaster condition. Disaster roaming refers to a special roaming policy applied during the disaster condition.

[0048] In another embodiment, the term Registered for Disaster Roaming Services refers to a state where the UE (101) has successfully completed an initial registration or a mobility registration for Disaster Roaming Services on 5GS, including optionally an attach procedure or a tracking area update procedure for Disaster Roaming Services on EPS. Initial registration for Disaster Roaming Services refers to a registration performed with a 5th Generation System (5GS) registration type designated as "disaster roaming initial registration" in the REGISTRATION REQUEST message. Mobility Registration for Disaster Roaming Services refers to a registration performed with a 5GS registration type designated as "disaster roaming mobility registration updating" in the REGISTRATION REQUEST message. Registration for disaster roaming refers to at least one of the initial registration for disaster roaming services and the mobility registration for disaster roaming services. In the EPS, the UE (101) shall perform an attach procedure with the EPS attach type set to "disaster roaming attach", or a tracking area updating procedure with the EPS update type set to "disaster roaming update". At step S1, during the disaster condition, a disaster inbound roamer acquires a forbidden PLMN, such as FPLMN-A (102), to avail services by sending an uplink NAS signaling message (e.g., a REGISTRATION REQUEST message) to the FPLMN-A (102) network with a Registration Type value indicating "Disaster Roaming Initial Registration" or "Disaster Roaming Mobility Registration Update." This Registration Type value signals to the FPLMN-A (102) network that the registration attempt is being performed under disaster roaming circumstances. A disaster inbound roamer refers to the UE (101) that cannot obtain service from the PLMN normally serving the UE (101) due to service failure during the disaster condition and is capable of registering with another PLMN.

[0049] At step S2, the FPLMN-A (102) accepts the disaster inbound roamer registration request and sends a downlink NAS signaling message (e.g., a REGISTRATION ACCEPT message) to the UE (101). In addition to accepting the registration request, the FPLMN-A (102) also provides an EPLMN list to the UE (101) for disaster roaming. This EPLMN list contains a PLMN present in the forbidden PLMN list of the UE (101), such as FPLMN-B, which is capable of providing disaster roaming service.

[0050] At steps S3 and S4, a scenario is considered where the UE (101) moves to a geographic area where only FPLMN-B is available for providing disaster roaming services. This movement creates a situation requiring network reselection to maintain disaster roaming services. The UE (101) may delete FPLMN-B from the EPLMN list provided by FPLMN-A (102) according to prior art procedures. Deleting FPLMN-B from the EPLMN list causes the UE (101) to fail to acquire any PLMN to obtain service in the disaster condition. Since FPLMN-B is not part of the EPLMN list, the UE (101) may not perform cell reselection procedures, impacting disaster roaming services and resulting in service unavailability during the ongoing disaster condition, despite the network's prior indication that FPLMN-B is capable of providing disaster roaming services.

[0051] FIG. 2 is a sequence diagram that illustrates a process of the UE (101) obtaining disaster roaming services from the PLMNs included in the FPLMN list during a disaster condition according to prior art. Preconditions may establish that the disaster roaming process is initiated only when the disaster condition has occurred and no other PLMN is available to the UE (101) except for PLMNs that are present in the forbidden PLMN list of the UE (101) or allowable PLMNs unable to provide the EPS services or 5GS services. This precondition confirms that disaster roaming services are restricted to genuine emergency scenarios where conventional network access is unavailable.

[0052] At step S1, the UE (101) transmits an uplink NAS message, specifically a REGISTRATION REQUEST message, to the FPLMN-A (102) for the purpose of disaster roaming services. The registration request includes the Registration Type parameter indicating either "Disaster Roaming Initial Registration" or "Disaster Roaming Mobility Registration Update" to inform the network that the registration is being performed under disaster conditions rather than normal circumstances.

[0053] In step S2, the FPLMN-A (102) accepts the disaster inbound roamer registration request and sends a downlink NAS signaling message, for example, a REGISTRATION ACCEPT message. In addition to accepting the registration, FPLMN-A (102) also provides the EPLMN list to the UE (101) for disaster roaming. The EPLMN list includes the PLMN, which is in the UE's forbidden PLMN list, for example, FPLMN-B, which is capable of providing disaster roaming service. This enables the UE (101) to become aware of other forbidden networks that may provide equivalent disaster roaming capabilities.

[0054] At step S3, the UE (101) establishes a PDU session for the emergency services. Subsequently, at step S4, the emergency PDU session is released.

[0055] In step S5, the existing system requires the UE (101) to delete the forbidden PLMNs from the list of equivalent PLMNs. According to technical specification TS 24.501, if the UE (101) is not registered for emergency services and an emergency PDU session has been established, the UE (101) may remove from the list of equivalent PLMNs any PLMN code present in the forbidden PLMN list as specified in subclause 5.3.13A when the emergency PDU session is released. FPLMN-B, being part of the forbidden PLMN list of the UE (101), is deleted from the list of equivalent PLMNs in accordance with the current specification requirements. This deletion prevents the UE (101) from moving to FPLMN-B through cell reselection procedures despite FPLMN-A (102) and FPLMN-B being equivalent PLMNs explicitly designated for disaster roaming purposes. The removal of FPLMN-B from the equivalent PLMN list creates an operational problem by limiting the mobility and service continuity of the UE (101) during ongoing disaster conditions.

[0056] To overcome the aforementioned disadvantages, the present invention provides a technical solution for supporting disaster condition functionality in the 3GPP system. The present invention enables the UE (101) to obtain information about the disaster condition affecting the PLMN. Mechanisms are provided for informing PLMN operators of affected geographic areas and allowing Disaster Inbound Roamers to receive communication services within the affected geographic areas. The invention also includes mechanisms to inform the UE (101) when a Disaster Condition ends and to minimize network congestion resulting from Disaster Roaming procedures. Furthermore, the present invention enables the UE (101) to access PLMNs present on the forbidden PLMN list during a Disaster Condition when no other PLMNs are available for network access. Mechanisms for generating charging information for Disaster Inbound Roamers, including details about the applied Disaster Condition parameters, are also provided.

[0057] FIG. 3 is a block diagram illustrating the UE (101) for managing the EPLMN list for disaster roaming services in a wireless communication network system according to embodiments disclosed herein. Examples of the UE (101) include, but are not limited to, Consumer Electronics (such as Mobile Phones and Smartphones), Tablets, Wearable Devices, Television, Computing Devices (such as Laptops, Notebooks, Desktops, Workstations, etc.), IoT Devices, Automotive Systems (such as connected cars, Autonomous Vehicles, Vehicle-to-Everything (V2X) communication devices, etc.), Enterprise Devices such as robotics, Specialized Equipment (such as Medical Devices, Public Safety Devices, etc.), and Media Devices (such as Gaming Consoles, Streaming Devices, etc.).

[0058] Examples of the wireless communication network system include, but are not limited to, Cellular Networks (such as 2G, 3G, 4G, 5G, Beyond 5G (B5G) / 6G, or advanced cellular networks), Local Area Networks (LANs) (such as Wi-Fi, Li-Fi, etc.), Personal Area Networks (PANs) (such as Bluetooth, Zigbee, Z-Wave, etc.), Wide Area Networks (WANs) (such as Satellite Communication Networks, Long Range Wide Area Network, Narrowband IoT, Low-bandwidth communication for IoT, etc.), Metropolitan Area Networks (MANs), Machine-to-Machine (M2M), Ad Hoc and Mesh Networks, and Emerging and Advanced Networks.

[0059] The UE (101) includes a processor (301), memory (303), an I / O interface (302), and an EPLMN list controller (304). The processor (301) of the UE (101) communicates with the memory (303), the I / O interface (302), and the EPLMN list controller (304). Configured to execute instructions stored in the memory (303), the processor (301) performs various processes. The processor (301) can include one or a plurality of processors and can be a general-purpose processor such as a central processing unit (CPU), an application processor (AP), or the like, a graphics-only processing unit such as a graphics processing unit (GPU), a visual processing unit (VPU), and / or an Artificial Intelligence (AI) dedicated processor such as a neural processing unit (NPU).

[0060] The memory (303) of the UE (101) includes storage locations addressable through the processor (301). The memory (303) is not limited to volatile memory and non-volatile memory and can include one or more computer-readable storage media. Non-volatile storage elements can include magnetic hard discs, optical discs, floppy discs, flash memories, or forms of electrically programmable memories (EPROM) or electrically erasable and programmable (EEPROM) memories. The memory (303) stores configuration information and parameters associated with disaster roaming operations and PLMN list management. It includes storage for the forbidden PLMN list, the EPLMN list received during disaster roaming registration, disaster condition status indicators, Registration Type values indicating disaster roaming procedures, Non-Access Stratum (NAS) signaling message parameters, PLMN identifiers including Mobile Country Code (MCC) and Mobile Network Code (MNC), disaster roaming service availability information, Tracking Area Identity (TAI) list comprising registration area parameters, and cell reselection criteria for disaster-capable networks.

[0061] The I / O interface (302) transmits information between the memory (303) and external peripheral devices. These peripheral devices are the input-output devices associated with the UE (101). The I / O interface (302) receives several pieces of information from the UE (101).

[0062] The EPLMN list controller (304) is coupled to the memory (303) and the processor (301), allowing efficient data transfer and communication between the components. This coupling ensures that the EPLMN list controller (304) can access and process disaster roaming PLMN list data in real-time. The EPLMN list controller (304) is an innovative integrated circuit implemented in the UE (101). In an embodiment, the structure of the innovative integrated circuit includes a multi-core architecture enabling dynamic management of EPLMN list retention during disaster roaming operations in a wireless communication network system. Each core is optimized for specific tasks such as determining whether registration procedures are performed as part of disaster roaming based on Registration Type values or attach procedure and tracking area update procedure are performed as part of part of disaster roaming based on attach type value or EPS update type value, identifying forbidden PLMNs present in the EPLMN list received from the serving network, preventing deletion of disaster-capable PLMNs from the EPLMN list upon emergency Protocol Data Unit (PDU) session release or emergency Packet Data Network (PDN) connection release, managing selective retention of forbidden PLMNs in the EPLMN list based on disaster roaming context, and enabling cell reselection procedures among disaster-capable networks present in the EPLMN list. The innovative integrated circuit for managing disaster roaming EPLMN list operations is composed of a combination of analog and digital components designed to optimize PLMN list retention accuracy and disaster roaming service continuity. The analog components include a high-precision timing circuit to ensure accurate disaster condition monitoring and EPLMN list evaluation timing, while the digital components include a microcontroller unit (MCU) and a digital signal processor (DSP) operating in tandem to dynamically manage EPLMN list retention based on disaster roaming registration context, forbidden PLMN list status, and emergency session release events during disaster condition scenarios.

[0063] The EPLMN list controller (304) determines that a disaster condition has occurred and no other PLMNs are available except for PLMNs in a forbidden PLMN list or allowable PLMNs unable to provide the EPS services or 5GS services. It transmits a Non-Access Stratum (NAS) request message to a first PLMN (for example, FPLMN-A (102)). The NAS request message includes a registration type value indicating disaster roaming initial registration or disaster roaming mobility registration update or attach type value indicating disaster roaming attach or EPS update type value indicating disaster roaming update. The EPLMN list controller (304) receives a NAS accept message from the first PLMN. The NAS accept message includes the equivalent PLMNs IE (information elements) having equivalent PLMNs capable of providing disaster roaming services. The EPLMN list controller (304) stores the Equivalent PLMNs received from the first PLMN as a "list of equivalent PLMNs." The UE (101) does not remove PLMNs from the "list of equivalent PLMNs" even when the PLMNs are available in the list of forbidden PLMNs in the UE (101).

[0064] In an embodiment, the EPLMN list controller (304) may include NAS accept . Further,the NAS accept message may include one of a registration accept message, an attach accept message, or a tracking area update accept message. The NAS accept message further includes a tracking area identity (TAI) list defining a one of the registration area or TAI lists. The registration area incldues TAIs of the first PLMN and of the second PLMN.

[0065] The EPLMN list controller (304) detects that the UE (101) has moved to a location where a second PLMN (for example, FPLMN-B (501)) from the "list of equivalent PLMNs" is available for providing disaster roaming services. It triggers a NAS procedure on the second PLMN to obtain the disaster roaming services. The second PLMN was part of the list of forbidden PLMNs at the UE (101) and is also included in the Equivalent PLMNs IE received by the first PLMN during the NAS procedure to obtain disaster roaming services. The EPLMN list controller (304) continues to use the disaster roaming services from the second PLMN.

[0066] The EPLMN list controller (304) triggers the NAS procedure and performs a cell reselection to move between PLMNs in the equivalent PLMN list as long as the UE (101) remains within a registration area that includes Tracking Area Identifiers (TAIs) of both the first PLMN and the forbidden PLMN. It triggers a NAS procedure upon moving out of the registration area.

[0067] The EPLMN list controller (304) includes the list of equivalent PLMNs, which includes at least one PLMN that may be in the list of forbidden PLMNs available at the UE (101). Further, the EPLMN list controller (304) may include the registration type value. Further, registration type value indicating "disaster roaming initial registration" or "disaster roaming mobility registration update", the attach type value indicating "disaster roaming attach", or the EPS update type value indicating "disaster roaming update" is included in one of a Registration Request message, an Attach Request message, or a Tracking Area Update (TAU) Request message.

[0068] The EPLMN list controller (304) determines whether the UE (101) is in at least one of an automatic network selection mode or a manual network selection mode (as specified in TS 23.122). It processes a NAS accept message that includes a Tracking Area Identity (TAI) list defining one of a registration area or a TAI list. The registration area includes TAIs of a first PLMN and a second PLMN.

[0069] The EPLMN list controller (304) determines that a disaster condition has terminated based on at least one of an emergency PDU session being established or emergency bearer services being released. It retains the list of equivalent PLMNs, including a PLMN identifier that is present in the forbidden PLMN list of the UE (101), in response to determining that the UE (101) is registered for disaster service.

[0070] FIG. 4 is a flow chart illustrating a method for managing an EPLMN list for disaster roaming services in a wireless communication network system according to embodiments disclosed herein.

[0071] At step 401, the method includes determining that a disaster condition has occurred and that no other PLMNs are available except for those in the forbidden PLMN list or allowable PLMNs unable to provide the EPS services or 5GS services. This determination is performed by the UE (101).

[0072] At step 402, the method includes transmitting the NAS request message to the first PLMN. The UE (101) performs this transmission. The NAS request message includes the registration type value indicating disaster roaming initial registration, disaster roaming mobility registration update, an attach type value indicating disaster roaming attach, or the EPS update type value indicating disaster roaming update.

[0073] At step 403, the method includes receiving the NAS accept message from the first PLMN. The UE (101) performs this reception. The NAS accept message includes equivalent PLMN information elements (IE) that have equivalent PLMNs capable of providing disaster roaming services.

[0074] At step 404, the method includes storing the equivalent PLMNs received from the first PLMN as a list of equivalent PLMNs. The UE (101) performs this storage. The UE (101) does not remove PLMNs from the list of equivalent PLMNs even when such PLMNs are present in the forbidden PLMN list of the UE (101).

[0075] FIG. 5 is a sequence diagram that illustrates a process for the UE (101) to retain all PLMNs in the EPLMN list including PLMNs from the forbidden PLMN list of the UE (101) according to embodiments as disclosed herein. Specifically, the process in which the UE (101) does not delete any PLMN from the EPLMN list even when the EPLMN list consists of PLMN from the forbidden PLMN list of the UE (101).

[0076] Further, the precondition establishes that the UE (101) shall be able to avail the MINT service only when the disaster condition has occurred and no other PLMN is available except for the PLMNs in the forbidden PLMN list of the UE (101). The precondition confirms that disaster roaming services are initiated exclusively during genuine disaster scenarios.

[0077] At step S1, in the disaster condition, the disaster inbound roamer acquires the forbidden PLMN, (for example FPLMN-A (102)) to avail services by sending the uplink NAS signaling message (for example a REGISTRATION REQUEST message) to the FPLMN-A (102) network with the Registration Type value indicating "Disaster Roaming Initial Registration" or "Disaster Roaming Mobility Registration Update". The Registration Type value signals to the FPLMN-A (102) network that the registration attempt may be performed under disaster roaming circumstances. Alternatively, At the step S1, disaster inbound roamer may acquire allowable PLMN (e.g. PLMN-A) unable to provide the EPS services or 5GS services but offering the disaster roaming services.

[0078] At step S2, the FPLMN-A (102) accepts the disaster inbound roamer registration request and sends the downlink NAS signaling message (for example a REGISTRATION ACCEPT message) to the UE (101). In addition to accepting the registration request, the FPLMN-A (102) also provides the equivalent PLMN list (EPLMN list) to the UE (101) for disaster roaming. The EPLMN list contains a PLMN that is present in the forbidden PLMN list of the UE 101, for example FPLMN-B (501), where the FPLMN-B (501) is capable of providing disaster roaming service.

[0079] At step S3, the UE (101) stores the EPLMN list provided by the FPLMN-A (102) as 'list of PLMN(s) to be used in the disaster condition'. The UE (101) considers the fact that the registration may be performed as part of disaster roaming and does not remove the PLMN from the EPLMN list received from the FPLMN-A (102) when such PLMN is the forbidden PLMN in the UE (101) (for example FPLMN-B (501)). In other words, the UE (101) may remove the PLMN from the EPLMN list received in the registration accept message when the UE (101) is not performing disaster roaming registration. This confirms that the UE (101) retains all disaster-capable PLMNs in the EPLMN list regardless of the forbidden PLMN list status during disaster roaming operations.

[0080] At step S4, a scenario is considered in which the UE (101) moves to a geographic area in which only FPLMN-B (501) is available for providing disaster roaming services. The movement of the UE (101) to the geographic area triggers the need for the UE (101) to evaluate available PLMNs for disaster roaming service continuity.

[0081] At step S5, the FPLMN-B (501) may be a part of the forbidden PLMN list of the UE (101), the FPLMN-B (501) is present in the EPLMN list provided by the FPLMN-A (102) during registration for disaster roaming. According to step S3, the UE (101) did not remove the FPLMN-B (501) from the EPLMN list and considers registering on the FPLMN-B (501) to obtain disaster roaming service. Further, the UE (101) may send an uplink NAS message (for example a REGISTRATION REQUEST message) to the FPLMN-B (501) for disaster roaming services. Additionally, the UE (101) continues to use the disaster roaming services from the FPLMN-B (501), thereby maintaining service continuity during the ongoing disaster condition.

[0082] In an embodiment, the Access and Mobility Management Function (AMF) may also include a list of equivalent PLMNs (Equivalent PLMNs Information element (IE)) in the REGISTRATION ACCEPT message. The inclusion further enhances the ability of the UE (101) to identify and register with suitable networks during disaster conditions, ensuring reliable connectivity.

[0083] In an embodiment, each entry in the list includes a PLMN code (MCC+MNC). The UE (101) shall store the list as provided by the network, and if the initial registration procedure is not for emergency services or not for the Disaster roaming service, the UE (101) may handle the EPLMN list accordingly. The handling ensures that the UE (101) may differentiate between standard and disaster conditions, applying the appropriate network selection criteria to maintain optimal service availability.

[0084] In an embodiment, the UE (101) may remove from the list any PLMN code already present in the forbidden PLMN list as specified in subclause 5.3.13A.

[0085] In an embodiment, The AMF may also include a list of equivalent PLMNs in the REGISTRATION ACCEPT message , The UE (101) shall store the list (i.e list of equivalent PLMNs) as provided by the network), and if the initial registration procedure is not for emergency services or not for the disaster roaming services, the UE shall remove from the list any PLMN code that is already in the forbidden PLMN list as specified in subclause　5.3.13A (i.e. "forbidden PLMNs for GPRS service" or list of "forbidden PLMNs").

[0086] In an embodiment, in the Mobility and periodic registration update accepted by the network, The AMF may also include a list of equivalent PLMNs in the REGISTRATION ACCEPT message. Each entry in the list contains a PLMN code (MCC+MNC). The UE (101) shall store the list as provided by the network, and if there is no emergency PDU session established or UE (101) is not registered for disaster roaming services or the UE (101)has not indicated registration type value "disaster roaming mobility registration update" in the REGISTRATION REQUEST, the UE shall remove from the list any PLMN code that is already in the forbidden PLMN list (i.e. "forbidden PLMNs for GPRS service" or list of "forbidden PLMNs").as specified in subclause　5.3.13A.

[0087] In an embodiment, if the Tracking Area Identity (TAI) list, being the registration area, includes the TAIs of both FPLMN-A (102) and FPLMN-B (501), by using the present invention, the UE (101) may move between FPLMN-A (102) and FPLMN-B (501) using the cell reselection procedure as long as the UE (101) is in the registration area. Once the UE (101) moves out of the registration area, the UE (101) may trigger the registration procedure.

[0088] In an embodiment, the FPLMN-A (102) and FPLMN-B (501) may be taken as example for the PLMN identity consisting of MCC (mobile country code) and MNC. The FPLMN-A (102), FPLMN-B (501) or any FPLMN (Forbidden PLMNs) is a PLMN identity present in at least one of the lists of "forbidden PLMNs for GPRS service" or list of "forbidden PLMNs" as specified in TS 24.501.

[0089] In an embodiment, allowable PLMNs (e.g PLMN-A) unable to provide the EPS services or 5GS services (i.e. the PLMN-A is available but UE (101) is unable to attempt to initiate NAS message e.g. registration request / attach request or tracking area update request for the normal service (also referred as EPS service or 5GS service) inlcudes a) UE (101)camped or found a cell whose tracking area (TAI-tracking area identifier) is in the list of "forbidden tracking areas for roaming", or the list of "forbidden tracking areas for regional provision of service" "5GS forbidden tracking areas for roaming", "5GS forbidden tracking areas for regional provision of service" b). the PLMN is the PLMNs with associated access technology restrictions and the access is restricted (e.g. UE found the PLMN in the E-UTRAN and the E-UTRAN is restricted) or UE found the PLMN but the capability is disabled (e.g. UE found the PLMN on the E-UTRAN but the E-UTRA capability is disabled for the PLMN due to the EMM reject cause #15 and the PLMN is stored in the list of "PLMNs with E-UTRAN not allowed" or UE found the PLMN on the NG-RAN but the N1 mode capability for the 3GPP access for the PLMN is disabled for the PLMN due to the 5GMM reject cause #27 "N1 mode not allowed" and the PLMN is stored in the list of PLMNs where N1 mode is not allowed for 3GPP access as specified in the TS 23.122) etc.

[0090] In an embodiment, the UE (101)determining that a disaster condition has occurred and that no other PLMNs are available except for those in the forbidden PLMN list or allowable PLMNs unable to provide the EPS services or 5GS services means that, these PLMNs are offering the disaster roaming services. The PLMN offering disaster roaming service broadcast the PLMN ID of the UE (101) determined PLMN with disaster condition or broadcasting the disaster related indication as specified in TS 23.122.

[0091] The present invention also applies to the case where the UE (101) is registered / attached for disaster roaming services on the EPC / LTE / EPS and receives the Equivalent PLMNs in the attach accept or tracking area update accept or any other NAS message. In the case, the UE (101) may use the complete Equivalent PLMNs for the disaster roaming for cell (re-)selection and does not delete any PLMNs from the Equivalent PLMNs even when PLMN(s) in the Equivalent PLMNs is in the list of "forbidden PLMNs for GPRS service" or list of "forbidden PLMNs".

[0092] In an embodiment, the UE (101) is considered as "attached for disaster roaming services" in EPS when it has successfully completed attach or tracking area update for disaster roaming services.

[0093] In an embodiment, the MME (mobility management entity) may also include a list of equivalent PLMNs in the ATTACH ACCEPT message or TRACKING AREA UPDATE ACCEPT message. Each entry in the list contains a PLMN code (MCC+MNC). The UE (101) may store the list as provided by the network, and if the attach procedure or tracking area update procedure is not for emergency services or disaster roaming service or the UE (101) is not registered for the disaster roaming service.

[0094] In an embodiment, The MME may also include a list of equivalent PLMNs in the ATTACH ACCEPT message. Each entry in the list contains a PLMN code (MCC+MNC). The UE shall store the list as provided by the network, and if the attach procedure is not for emergency bearer services or not for access to RLOS or not for disaster roaming services, the UE shall remove from the list any PLMN code that is already in the list of "forbidden PLMNs" or in the list of "forbidden PLMNs for GPRS service".

[0095] In an embodiment, The MME may also include a list of equivalent PLMNs in the TRACKING AREA UPDATE ACCEPT message. Each entry in the list contains a PLMN code (MCC+MNC). The UE shall store the list as provided by the network, and if there is no PDN connection for emergency bearer services or PDN connection for RLOS established or the UE is not attached for disaster roaming services or UE has not indicated EPS update type value to "disaster roaming update" in the TRACKING AREA UPDATE REQUEST message, the UE shall remove from the list any PLMN code that is already in the list of "forbidden PLMNs" or in the list of "forbidden PLMNs for GPRS service".

[0096] FIG. 6 is a sequence diagram illustrating a process for retaining PLMNs in the equivalent PLMN list during disaster roaming in a 5G system according to embodiments disclosed herein. The precondition establishes that the UE (101) can avail the MINT services only when a disaster condition has occurred and no other PLMN is available except for PLMNs included in the forbidden PLMN list of the UE (101). This precondition confirms that disaster roaming services are triggered exclusively during emergency scenarios.

[0097] In step S1, during the disaster condition, the disaster inbound roamer acquires the forbidden PLMN (for example, FPLMN-A (102)) to avail services by sending the uplink NAS signaling message (for example, a REGISTRATION REQUEST message) to the FPLMN-A (102) network with the Registration Type value indicating "Disaster Roaming Initial Registration" or "Disaster Roaming Mobility Registration Update." The Registration Type value signals to the FPLMN-A (102) network that the registration attempt may be performed under disaster roaming circumstances.

[0098] At step S2, the FPLMN-A (102) provides the EPLMN list, including FPLMN-B (502), to the UE (101) in the downlink NAS message (for example, a REGISTRATION ACCEPT message). The EPLMN list includes the PLMN that is present in the forbidden PLMN list of the UE (101) (for example, FPLMN-B (501)). The FPLMN-B (501) is capable of providing disaster roaming service.

[0099] Step S3 involves the UE (101) considering the fact that the EPLMN list may be sent during registration for disaster roaming. The UE (101) does not delete any PLMN from the EPLMN list even when the EPLMN list consists of PLMN from the forbidden PLMN list of the UE (101). The UE (101) stores the EPLMN list provided by the FPLMN-A (102) as a list of PLMN(s) to be used in Disaster Condition. The UE (101) acknowledges that the registration was performed as part of disaster roaming and does not remove PLMN from the EPLMN list received from the FPLMN-A (102) when such PLMN is the forbidden PLMN in the UE (101) (for example, FPLMN-B (501)). In other words, the UE (101) may remove the PLMN from the EPLMN list received in the registration accept message when the UE (101) is not performing disaster roaming registration.

[0100] At step S4, the UE (101) establishes an emergency PDU session for emergency services. This emergency PDU session enables the UE (101) to access emergency communication capabilities while registered on the disaster roaming network.

[0101] Step S5 involves the release of the emergency PDU session after the emergency communication has been completed. The release of the emergency PDU session triggers the evaluation of the EPLMN list by the UE (101).

[0102] Further, at step S6, the UE (101) retains the list of equivalent PLMNs and does not delete the PLMNs from the list of equivalent PLMNs even when the PLMNs are forbidden PLMNs. The FPLMN-B (501) is retained in the list of equivalent PLMNs, thereby enabling the UE (101) to maintain network mobility and service continuity during the ongoing disaster condition. The retention of forbidden PLMNs in the equivalent PLMN list ensures that the UE (101) may access multiple disaster-capable networks as provided by the FPLMN-A (102) during disaster roaming registration.

[0103] In an embodiment, if the UE (101) is not registered for emergency services and the UE (101) is not registered for the disaster roaming service and there is an emergency PDU session established, the UE (101) shall remove from the list of equivalent PLMNs any PLMN code present in the forbidden PLMN list as specified in subclause　5.3.13A, when the emergency PDU session is released.

[0104] FIG. 7 is a sequence diagram illustrating the process for retaining PLMNs in the equivalent PLMN list during disaster roaming in an Evolved Packet System (EPS) according to disclosed embodiments. The precondition establishes that the UE (101) may avail MINT service only when a disaster condition has occurred and no other PLMN is available except for PLMNs in the forbidden PLMN list of the UE (101). This precondition confirms that disaster roaming services are initiated exclusively during genuine emergency scenarios.

[0105] In step S1, during the disaster condition, the disaster inbound roamer acquires the forbidden PLMN (e.g., FPLMN-A (102)) to avail services by sending an uplink NAS signaling message (e.g., an ATTACH REQUEST message or TRACKING AREA UPDATE REQUEST message) to the FPLMN-A (102) network. This message includes an attach type value indicating disaster roaming attach or an EPS update type value indicating disaster roaming update, signaling to the FPLMN-A (102) network that the request is being performed under disaster roaming circumstances.

[0106] At step S2, the FPLMN-A (102) accepts the disaster inbound roamer's attach request or tracking area update request and sends a downlink NAS signaling message (e.g., an ATTACH ACCEPT message or TRACKING AREA UPDATE ACCEPT message) to the UE (101). Along with accepting the request, the FPLMN-A (102) provides the equivalent PLMN list (EPLMN list) containing FPLMN-B (501) to the UE (101) for disaster roaming. This EPLMN list includes PLMNs from the forbidden PLMN list of the UE (101) that are capable of providing disaster roaming service.

[0107] In step S3, the UE (101) acknowledges that the EPLMN list was sent during registration for disaster roaming. The UE (101) does not delete any PLMN from the EPLMN list, even if it includes PLMNs from the forbidden PLMN list. The UE (101) stores the EPLMN list provided by the FPLMN-A (102) as a list of PLMNs to be used in a disaster condition. The UE (101) considers the registration as part of disaster roaming and does not remove PLMNs from the EPLMN list received from the FPLMN-A (102) when such PLMNs are forbidden PLMNs in the UE (101) (e.g., FPLMN-B). Conversely, the UE (101) may remove PLMNs from the EPLMN list received in the attach accept message or tracking area update accept message when not performing disaster roaming registration.

[0108] Step S4 involves the establishment of a PDN connection for emergency bearer services by the UE (101). This connection enables the UE (101) to access emergency communication capabilities while registered on the disaster roaming network.

[0109] In step S5, the PDN connection for emergency bearer services is released after the emergency communication has been completed. The release triggers the evaluation of the EPLMN list by the UE (101).

[0110] Further, in step S6, the UE (101) retains the list of equivalent PLMNs and does not delete PLMNs from this list, even if they are forbidden PLMNs. The retention of FPLMN-B (501) in the equivalent PLMN list ensures that the UE (101) maintains network mobility and service continuity during the ongoing disaster condition. This retention guarantees that the UE (101) can access multiple disaster-capable networks as provided by the FPLMN-A (102) during disaster roaming registration in the EPS.

[0111] In an embodiment, if the UE (101) is not attached for emergency bearer services or UE is not attached for the disaster roaming services and there is a PDN connection for emergency bearer services established, the UE (101) shall remove from the list of equivalent PLMNs any PLMN code present in the list of forbidden PLMNs or in the list of "forbidden PLMNs for GPRS service" when the PDN connection for emergency bearer services is released.

[0112] The present invention offers a technical solution to address significant limitations in existing disaster roaming implementations. It enables the UE (101) to retain forbidden PLMNs in the EPLMN list during disaster conditions. By preventing the automatic deletion of disaster-capable networks from the EPLMN list upon emergency Protocol Data Unit (PDU) session release in the 5G System (5GS) or emergency Packet Data Network (PDN) connection release in the EPS, the invention ensures that the UE maintains continuous access to multiple disaster roaming networks as explicitly designated by the serving network.

[0113] A context-aware mechanism is disclosed by the present invention for differentiating between normal registration procedures and disaster roaming registration procedures. This mechanism allows the UE (101) to apply appropriate handling of the EPLMN list based on the registration context. Continuous mobility between disaster-capable networks is enabled through cell reselection procedures without requiring repeated registration attempts, thereby reducing network signaling overhead and minimizing service interruptions during critical disaster scenarios.

[0114] Uniform application of the invention across both 5GS and EPS architectures provides consistent disaster roaming behavior across different network technologies and ensures backward compatibility with existing network infrastructure. The integrity of the EPLMN list is maintained throughout the disaster condition lifecycle, enhancing the reliability and effectiveness of MINT services. Affected users can maintain critical communication capabilities and emergency service access throughout disaster scenarios by leveraging multiple network operators' infrastructure as intended by the disaster roaming framework. This achieves the objective of providing resilient and continuous communication services during emergency situations.

[0115] FIG. 8 is a block diagram of a base station (BS) 800 according to an embodiment of the disclosure.

[0116] The BS 800 may perform wireless communication with at least one user equipment (UE) located within the area of the BS 800 through a wireless channel. The BS 800 may perform communication with a node or an entity of a network through wired or wireless communication.

[0117] Referring to FIG. 8, the BS 800 may include at least one transceiver (hereinafter, referred to as simply "transceiver") 801, at least one processor (hereinafter, referred to as simply "processor") 802, and at least one memory (hereinafter, referred to as simply "memory") 803. According to at least one or a combination of methods corresponding to the embodiments described in the present disclosure, the transceiver 801, the processor 802, and the memory 803 of the BS 800 may operate. However, components of the BS 800 are not limited to the example components illustrated in FIG. 8. In another embodiment, the BS 800 may further include additional components in addition to the above-mentioned components, or some components may be omitted. Further, in some embodiments, any combination of the transceiver 801, the processor 802, or the memory 803 may be integrated in the form of one component.

[0118] The transceiver 801 may be a communication circuit or communication circuitry that enables the BS 800 to perform wireless communication with a node or an entity of a network. For example, the transceiver 801 may enable the BS 800 to transmit or receive a signal to or from the UE X00 through cellular communication, or to transmit or receive a signal to or from another network entity through wireless communication. For example, the transceiver 801 may support various cellular communication technologies including 3rd generation (3G), 4thgeneration (4G), long term evolution (LTE), 5th generation (5G) NR, 6thgeneration (6G), and various cellular wireless communication technologies supported by the transceiver (801) may include all subsequent generations of evolved wireless communications.. According to an embodiment, the transceiver 801 may include various circuit structures used to transmit or receive signals to or from a UE through a wireless channel. The signals may include control information and data. For example, the transceiver 801 may include a radio frequency (RF) transmitter for up-converting and amplifying the frequency of a transmitted signal and an RF receiver for low-noise-amplifying a received signal and down-converting the frequency thereof. The transceiver 801 may output a signal received through a wireless channel to the processor 802 and may transmit, through a wireless channel, a signal output from the processor 802.

[0119] Meanwhile, according to an embodiment of the present disclosure, the BS 800 may perform communication with a node or an entity of a network through wired or wireless communication. For example, the BS 800 may perform wired or wireless communication with an adjacent BS, or a node or an entity of a core network through a backhaul network. Although not illustrated in FIG. 8, when the BS 800 performs wired communication, the BS 800 may further include a separate network interface for wired communication in addition to the transceiver 801. The network interface may be referred to as network interface circuitry or communication interface circuitry.

[0120] The processor 802 may control general operations of the BS 800 according to embodiments of the disclosure. The processor 802 may be implemented by one or more integrated circuit (or circuitry) (IC) chips and may execute various data processing operations. The processor 802 may include at least one electric circuit, and may execute instructions (or a program, codes, data, etc.) stored in the memory 803, individually, collectively or in any combination thereof. Further, the processor 802 may include a single-core processor or multi-core processor, and may include a processor assembly including a plurality of processing circuits (circuitry) according to a specific implementation scheme.

[0121] The processor 802 may be electrically, operatively, and / or communicatively coupled to the transceiver 801 to control the transceiver 801.

[0122] The processor 802 may include at least one processor (or processing circuitry), and the at least one processor may perform the following operations individually, collectively or in any combination thereof. In a specific embodiment, at least a part of the processor 802 may be included in one chip (or IC) and the other part of the processor 802 may be included in another chip (or IC). Otherwise, at least one processor may be included in another component, for example, the transceiver 801 or the memory 803.

[0123] The processor 802 may perform or control or cause an operation of the BS 800 for executing at least one or a combination of methods according to embodiments of the disclosure. For example, the processor 802 may control operations of the BS 800 for generating and transmitting a downlink signal to a UE or processing an uplink signal received from a UE. Otherwise, the BS 800 may transmit or receive a signal to or from a neighboring BS, transfer a signal received from a UE to an upper node of the network, or transmit a signal transferred from an upper node of the network to a UE. To this end, the processor 802 may execute a computer program, codes, or instructions stored in the memory 803, so as to control other components of the BS 800 to enable execution of various operations.

[0124] The memory 803 corresponds to a hardware storage device capable of temporarily or permanently storing information and may include one or more storage media. For example, the memory 803 may include a memory assembly including one or more storage media. For example, the one or more storage media may include permanent memory, such as a hard drive, flash memory, or read-only memory (ROM), semipermanent memory, such as random access memory (RAM), cache memory, or a combination thereof.

[0125] The memory 803 may be electrically, operatively, and / or communicatively coupled to the processor 802 and may be accessed by the processor 802.

[0126] The memory 803 may store a computer program, codes, or instructions executable by the processor 802. According to an embodiment, a computer program, codes, or instructions executable by the processor 802 may be either stored in a single memory device or separated and distributedly stored in two or more memory devices. By executing the instructions stored in the memory 803, the processor 802 may perform various functions according to an embodiment of the disclosure.

[0127] According to an embodiment of the disclosure, operations of the BS 800 may be caused to be performed based on execution of instructions (or a computer program or codes) stored in the memory 803 by at least one processor (or processing circuitry) configured to execute the same individually, collectively, or in any combination thereof, based on processing circuitry that is not configured to execute instructions, and / or based on components of processing circuitry that is not configured to execute instructions.

[0128] The UE or the base station may perform various communication procedures related to the control plane or the user plane by cooperating with one or more network entities based on wireless communication. For example, the UE may communicate with a network entity (for example, an Access and Mobility Management Function (AMF), a Session Management Function (SMF), rtc.) via the base station, or the base station may perform at least one communication procedure by directly transmitting and receiving signals to / from, or relaying signals between, the network entities.

[0129] The structure of the above-described network entity will be described in more detail with reference to the drawings.

[0130] FIG. 9 is a block diagram of a network entity 900 according to an embodiment of the disclosure.

[0131] The network entity 900 may include an entity (apparatus, device, or server, etc.) that performs one or more network functions (NFs) or a part of a network function constituting a core network (e.g., a 5th generation (5G) core (5GC)) in a communication system. In this case, multiple NFs may be implemented within a single network entity, or a single NF may be distributed and implemented across a plurality of network entities. In addition, when an NF is implemented within the network entity, the NF may be implemented in the form of software, and in such a case, a program for operating the NF may be stored in memory of the network entity 900.

[0132] A single NF may be implemented by one or more instances, which may be deployed on the same network entity or distributed across multiple network entities to operate. The instance may be a software unit that logically executes a specific network function, and may be implemented in a form that is decoupled from physical hardware resources. Further, one or more NFs may be implemented in the form of one network slice to operate to satisfy specifications required by a particular service.

[0133] The NF may include at least one of an access and mobility management function (AMF), a session management function (SMF), a local session management function (L-SMF), a user plane function (UPF), a local user plane function (L-UPF), a policy control function (PCF), a unified data management (UDM), a unified data repository (UDR), a network exposure function (NEF), a network repository function (NRF), an application function (AF), a network slice selection function (NSSF), a network data analytics function (NWDAF), a network slice admission control function (NSACF), an authentication server function (AUSF), or a data network (DN), a mobility management entity (MME), etc.

[0134] Referring to FIG. 9, the network entity 900 may include at least one network interface 901, at least one processor 902 (hereinafter, "processor"), and at least one memory 903 (hereinafter, "memory"). As described above, a NF may be implemented in the form of a physical device such as the network entity 900, or may be virtualized and executed in the form of an instance. When implemented as an instance, the NF need not necessarily include physical components as illustrated in FIG. 9. In such a case, the instance may be logically represented as comprising one or more logical functional elements.

[0135] According to at least one or a combination of methods corresponding to the embodiments described in the present disclosure, the network interface 901, the processor 902, and the memory 903 of the network entity 900 may operate. However, components of the network entity 900 are not limited to the example components illustrated in FIG. 9. In another embodiment, the network entity 900 may further include additional components in addition to the above-mentioned components, or some components may be omitted. Further, in an embodiment, the network interface 901, the processor 902, or the memory 903 may be integrated in the form of one component.

[0136] The network interface 901 is a collective term for a transmitter part of the network entity 900 and a receiver part of the network entity 900, and may be a communication circuit for transmitting or receiving a signal to or from a user equipment (UE), a base station (BS), or another network entity. Here, the communication circuit may include both a communication circuit for wireless communication and a communication circuit for a wired communication. For example, the network interface 901 may include a circuit, logic, hardware, etc., configured to exchange a control plane message or a user plane message with a UE, a BS, or other core network entities through wireless communication or wired communication. The network interface 901 may operate using various protocols (e.g., non-access stratum (NAS) protocol). The network interface 901 may also be referred to, for convenience of description or depending on implementation, as communication circuitry, network interface circuitry, or a communication interface circuitry.

[0137] The processor 902 may control general operations of the network entity 900 according to embodiments of the disclosure. The processor 902 may be implemented by one or more integrated circuit (or circuitry) (IC) chips and may execute various data processing operations. The processor 902 may include at least one electric circuit, and may execute instructions (or a program, codes, data, etc.) stored in the memory 903, individually, collectively or in any combination thereof. Further, the processor 902 may include a single-core processor or multi-core processor, and may include a processor assembly including a plurality of processing circuits (circuitry) according to a specific implementation scheme. Further, it should be noted that, according to another embodiment, in a case where NF is implemented in the form of an instance, the network function may be not necessarily configured by physical hardware.

[0138] According to an embodiment, the processor 902 may be electrically, operatively, and / or communicatively coupled to the network interface 901 to control the network interface 901.

[0139] The processor 902 may include at least one processor (or processing circuitry), and the at least one processor may perform the following operations individually, collectively or in any combination thereof. In a specific embodiment, at least a part of the processor 902 may be included in one chip (or IC) and the other part of the processor 902 may be included in another chip (or IC). Otherwise, at least one processor may be included in another component, for example, the network interface 901 or the memory 903.

[0140] The processor 902 may perform or control or cause an operation of the network entity 900 for executing at least one or a combination of methods according to embodiments of the disclosure. For example, the processor 902 may control operations of the network entity 900 for exchanging a control plane message or a user plane message with a UE, a BS, or other core network entities through wireless or wired communication, using various protocols (e.g., NAS protocol). To this end, the processor 902 may execute a computer program, codes, or instructions stored in the memory 903, so as to control other components of the network entity 900 to enable execution of various operations.

[0141] The memory 903 corresponds to a hardware storage device capable of temporarily or permanently storing information and may include one or more storage media. For example, the memory 903 may include a memory assembly including one or more storage media. For example, the one or more storage media may include permanent memory, such as a hard drive, flash memory, or read-only memory (ROM), semipermanent memory, such as random access memory (RAM), cache memory, or a combination thereof.

[0142] The memory 903 may be electrically, operatively, and / or communicatively coupled to the processor 902 and may be accessed by the processor 902.

[0143] The memory 903 may store a computer program, codes, or instructions executable by the processor 902. According to an embodiment, a computer program, codes, or instructions executable by the processor 902 may be either stored in a single memory device or separated and distributedly stored in two or more memory devices. By executing the instructions stored in the memory 903, the processor 902 may perform various functions according to an embodiment of the disclosure.

[0144] According to an embodiment of the disclosure, operations of the network entity 900 may be caused to be performed based on execution of instructions (or a computer program or codes) stored in the memory 903 by at least one processor (or processing circuitry) configured to execute the same individually, collectively, or in any combination thereof, based on processing circuitry that is not configured to execute instructions, and / or based on components of processing circuitry that is not configured to execute instructions.

[0145] 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.

Claims

1.A method performed by a user equipment (UE) in a wireless communication network system, comprising:in case that a disaster condition is met, transmitting, to an entity for a mobility control associated with a first public land mobile network (PLMN), a request message for a registration procedure associated with disaster roaming services;receiving, from the entity for the mobility control associated with the first PLMN, an accept message comprising a list of equivalent PLMNs to be used in the disaster condition; andstoring the list of equivalent PLMNs received from the entity for the mobility control associated with the first PLMN,wherein, in case that the registration procedure is for the disaster roaming services, the UE does not remove any PLMN from the list of equivalent PLMNs that is already in a forbidden PLMN list in the UE.2.The method of claim 1, further comprising:detecting that the UE is moved to a location where a second PLMN from the list of equivalent PLMNs is available for providing the disaster roaming services;triggering a registration procedure on the second PLMN to obtain the disaster roaming services, wherein the second PLMN is in the forbidden PLMN list in the UE and is also included in the list of equivalent PLMNs IE received by first PLMN; andcontinuing to use the disaster roaming services from the second PLMN.3.The method of claim 1, wherein the list of equivalent PLMNs comprises at least one PLMN which is in the forbidden PLMN list available at the UE.4.The method of claim 1, wherein the request message comprises a registration type value indicating "disaster roaming initial registration" or "disaster roaming mobility registration update", an attach type value indicating "disaster roaming attach", or an EPS update type value indicating "disaster roaming update."5.The method of claim 1, wherein the request message comprises at least one of a registration request message, an attach request message, or a tracking area update request message.6.The method of claim 1, wherein the accept message comprises at least one of a registration accept message, an attach accept message, or a tracking area update accept message, andwherein the accept message further comprises a tracking area identity (TAI) list defining a one of the registration area or TAI lists, and wherein the registration area comprises TAIs of the first PLMN and of the second PLMN.7.The method of claim 1, wherein, in case that the UE is not registered for the disaster roaming services and there is an emergency protocol data unit (PDU) session established, the UE removes from the list of equivalent PLMNs any PLMN presented in the forbidden PLMN list in the UE, when the emergency PDU session is released.8.A user equipment (UE) in a wireless communication network system, comprising:a transceiver; anda processor coupled with the transceiver and configured to:in case that a disaster condition is met, transmit, to an entity for a mobility control associated with a first public land mobile network (PLMN), a request message for a registration procedure associated with disaster roaming services,receive, from the entity for the mobility control associated with the first PLMN, an accept message comprising a list of equivalent PLMNs to be used in the disaster condition, andstore the list of equivalent PLMNs received from the entity for the mobility control associated with the first PLMN,wherein, in case that the registration procedure is for the disaster roaming services, the UE does not remove any PLMN from the list of equivalent PLMNs that is already in a forbidden PLMN list in the UE.9.The UE of claim 8, further comprising:detecting that the UE is moved to a location where a second PLMN from the list of equivalent PLMNs is available for providing the disaster roaming services;triggering a registration procedure on the second PLMN to obtain the disaster roaming services, wherein the second PLMN is in the forbidden PLMN list in the UE and is also included in the list of equivalent PLMNs IE received by first PLMN; andcontinuing to use the disaster roaming services from the second PLMN.10.The UE of claim 8, wherein the list of equivalent PLMNs comprises at least one PLMN which is in the forbidden PLMN list available at the UE.11.The UE of claim 8, wherein the request message comprises a registration type value indicating "disaster roaming initial registration" or "disaster roaming mobility registration update", an attach type value indicating "disaster roaming attach", or an EPS update type value indicating "disaster roaming update."12.The UE of claim 8, wherein the request message comprises at least one of a registration request message, an attach request message, or a tracking area update request message.13.The UE of claim 8, wherein the accept message comprises at least one of a registration accept message, an attach accept message, or a tracking area update accept message, andwherein the accept message further comprises a tracking area identity (TAI) list defining a one of the registration area or TAI lists, and wherein the registration area comprises TAIs of the first PLMN and of the second PLMN.14.The UE of claim 8, wherein, in case that the UE is not registered for the disaster roaming services and there is an emergency protocol data unit (PDU) session established, the UE removes from the list of equivalent PLMNs any PLMN presented in the forbidden PLMN list in the UE, when the emergency PDU session is released.15.An entity for a mobility control associated with a first public land mobile network (PLMN) in a communication network system, comprising:a transceiver; anda processor coupled with the transceiver and configured to:in case that a disaster condition is met, receiving, from a user equipment (UE), a request message for a registration procedure associated with disaster roaming services; andtransmitting, to the UE, an accept message comprising a list of equivalent PLMNs to be used in the disaster condition,wherein the list of equivalent PLMNs is stored in the UE, andwherein, in case that the registration procedure is for disaster roaming services, the UE does not remove any PLMN from the list of equivalent PLMNs that is already in a forbidden PLMN list in the UE.

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