Method and apparatus for handling timer in telecommunication network

Abstract

The disclosure relates to a 5G or 6G communication system for supporting a higher data transmission rate. The disclosure providesA method performed by a user equipment (UE) in a wireless communication, the method comprising: selecting a first public land mobile network (PLMN) for disaster roaming; upon selecting the first PLMN, in case that the UE has stored a disaster roaming wait range, generating a random number within the disaster roaming wait range; and starting a first timer with the generated random number within the disaster roaming wait range, wherein, while the first timer is running, a registration on the first PLMN is not initiated, except in case that the UE needs to request an emergency PDU session, wherein, in case that the first timer expires, a timer with a value based on the disaster roaming wait range is not started.

Description

METHOD AND APPARATUS FOR HANDLING TIMER IN TELECOMMUNICATION NETWORK

[0001] The present disclosure relates to wireless communication systems and, more specifically, to a method and apparatus for Minimization of service interruption (MINT) wait timer handling.

[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 embodiments herein is to provide a method and UE for handling a timer (e.g., MINT timer) in a telecommunication network.

[0009] Another object of the embodiments herein is to refrain from starting or running a timer within the disaster roaming wait range again until the disaster condition has ended, when the timer for disaster roaming wait range has expired.

[0010] Another object of the embodiments herein is to refrain from starting or running a timer within the disaster return wait range again until the UE selects a PLMN for a disaster roaming service, when the timer for disaster return wait range has expired.

[0011] Another object of the embodiments herein is to perform at least one of: a registration procedure, a Non-Access Stratum (NAS) signaling procedure, and an Access Stratum (AS) signaling procedure on a selected Public Land Mobile Network (PLMN) without waiting for the duration of the disaster roaming wait range or the disaster return wait range.

[0012] In an aspect, the objectives are achieved by providing method for handling a timer in a telecommunication network. The method includes detecting, by a User Equipment (UE), a disaster condition. The method includes running, by the UE, a timer for at least one of: a disaster roaming wait range and a disaster return wait range stored at the UE. Further, the method includes determining, by the UE, whether the timer has expired at least once after at least one of: the disaster condition has started and the disaster condition has ended. In an embodiment, the method includes refraining, by the UE, from starting or running a timer within the disaster roaming wait range again until the disaster condition has ended, when the timer for disaster roaming wait range has expired. In another embodiment, the method includes refraining, by the UE, from starting or running a timer within the disaster return wait range again until the UE selects a PLMN for a disaster roaming service, when the timer for disaster return wait range has expired.

[0013] In an aspect, the objectives are achieved by providing UE for handling a timer in a wireless network. The UE includes a MINT wait timer handling controller coupled with a processor and a memory. The memory stores one of a disaster roaming wait range or a disaster return wait range. The MINT wait timer handling controller detects a disaster condition. The MINT wait timer handling controller runs a timer for at least one of: a disaster roaming wait range and a disaster return wait range stored at the UE. The MINT wait timer handling controller determines whether the timer has expired at least once after at least one of: the disaster condition has started and the disaster condition has ended. In an embodiment, the MINT wait timer handling controller refrains from starting or running a timer within the disaster roaming wait range again until the disaster condition has ended, when the timer for disaster roaming wait range has expired. In an embodiment, the MINT wait timer handling controller refrains from starting or running a timer within the disaster return wait range again until the UE selects a PLMN for a disaster roaming service, when the timer for disaster return wait range has expired.

[0014] In an embodiment, the method includes performing, by the UE, at least one of: a registration procedure, a Non-Access Stratum (NAS) signaling procedure, and an Access Stratum (AS) signaling procedure on a selected Public Land Mobile Network (PLMN) without waiting for the duration of the disaster roaming wait range or the disaster return wait range, after the timer has expired at least once.

[0015] In an embodiment, running, by the User Equipment (UE), the timer for one of the disaster roaming wait range or the disaster return wait range includes generating, by the UE, a random number within one of the disaster roaming wait range or the disaster return wait range, and initiating, by the UE, the timer for a time duration corresponding to the generated random number.

[0016] In an embodiment, refraining, by the UE, from starting or running the timer within the disaster roaming wait range until the disaster condition has ended includes at least one of: preventing, by the UE, generation of another random number within the disaster roaming wait range, and preventing, by the UE, from starting or running a timer with a random number within the disaster roaming wait range until the disaster condition has ended.

[0017] In an embodiment, refraining, by the UE, from starting or running the timer within the disaster return wait range again until the UE selects the PLMN for the disaster roaming service includes at least one of: preventing, by the UE, generation of another random number within the disaster return wait range, and preventing, by the UE, from starting or running a timer with a random number within the disaster return wait range until the UE selects a PLMN for the disaster roaming service.

[0018] In an embodiment, the timer is started or run upon selecting a PLMN or a combination of PLMN and RAT for disaster roaming or upon determining that a disaster condition has ended in a PLMN or in a combination of PLMN and RAT.

[0019] These and other aspects of the embodiments herein will be better appreciated and understood when considered in conjunction with the following description and the accompanying drawings. It should be understood, however, that the following descriptions, while indicating 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 modification.

[0020] According to the embodiments of the present disclosure, service interruption can be minimized by preventing repeated waiting based on a disaster roaming wait range after expiry of a corresponding timer, thereby reducing unnecessary delay in obtaining service from a PLMN offering disaster roaming services.

[0021] Further, according to the embodiments of the present disclosure, service interruption can be minimized by preventing repeated waiting based on a disaster return wait range after expiry of a corresponding timer, thereby reducing unnecessary delay when the UE returns to a UE determined PLMN with disaster condition or another selected PLMN after a disaster condition has ended.

[0022] These and other features, aspects, and advantages of the present disclosure 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:

[0023] FIG 1A is a sequence diagram illustrating the existing solution where the UE starts the timer for the disaster roaming wait range again, even if the timer has already expired once, according to prior art.

[0024] FIG. 1B is a sequence diagram that illustrates the proposed method where upon expiry of the timer for disaster roaming wait range, the UE shall not start a timer with the disaster roaming wait range value again until disaster condition has ended.

[0025] FIG 2A is a sequence diagram illustrating the existing solution where the UE starts the timer for the disaster return wait range again, even if the timer has already expired once.

[0026] FIG. 2B is a sequence diagram that illustrates the proposed method where upon expiry of the timer for disaster return wait range, the UE shall not start a timer with the disaster return wait range value again until the UE selects a PLMN for disaster roaming services, according to embodiments of the disclosure.

[0027] FIG. 3 is a block diagram of the UE, according to embodiments of the disclosure.

[0028] FIG. 4 is a flow chart illustrating a method for handling the timer in a telecommunication network, according to embodiments of the disclosure.

[0029] FIG. 5 is a block diagram of a terminal or user equipment (UE) 500 according to an embodiment of the disclosure.

[0030] FIG. 6 is a block diagram of a base station (BS) 600 according to an embodiment of the disclosure.

[0031] FIG. 7 is a block diagram of a network entity 700 according to an embodiment of the disclosure.

[0032] Hereinafter, embodiments of the disclosure will be described in detail with reference to the accompanying drawings.

[0033] In describing the embodiments, while numerous details are set forth for the purpose of illustration, it is understood that some aspects of the disclosure may be practiced with less than all of these details. Numerous variations and alternatives to the details provided herein are possible and are considered within the scope of the disclosure. In some instances, descriptions related to technical contents well-known in the art may be omitted so as to not obscure an understanding of the disclosure, and such omitted descriptions are understood to be within the scope of the disclosure.

[0034] For the same reason, in the accompanying drawings, some elements may be exaggerated, omitted, or schematically illustrated. Further, the size of each element does not completely reflect the actual size. In the drawings, identical or corresponding elements are provided with identical reference numerals or different reference numerals.

[0035] The advantages and features of the disclosure and ways to achieve them will be apparent by making reference to embodiments as described herein in detail in conjunction with the accompanying drawings. However, the disclosure is not limited to the embodiments set forth herein, but may be implemented in various different forms. Other features, aspects, and advantages of the subject matter described herein will become apparent from the disclosure. The following embodiments are merely examples to aid in an understanding of the disclosure and should not be construed to narrow the scope or spirit of the subject matter described herein in any way, but on the contrary, the disclosure covers all modifications, equivalents and alternatives falling within the spirit and scope of the subject matter as defined by the appended claims and equivalents thereof. Throughout the specification, the same or like reference numerals designate the same or like elements. Furthermore, terms which will be described herein are terms defined in consideration of the functions in the disclosure, and may be different according to users, intentions of the operators, or customs. Therefore, the definitions of the terms should be made based on the contents throughout the specification.

[0036] Herein, it will be understood that each block of flowchart illustrations, and combinations of blocks in the flowchart illustrations, may be performed based on computer program instructions. These computer program instructions may be loaded collectively onto at least one processor of a general purpose computer, special purpose computer, or other programmable data processing apparatus to produce a machine, such that the instructions, which perform through any one of, or in any combination of, the at least one processor of the computer or other programmable data processing apparatus, create means for performing the functions specified in the flowchart block(s). These computer program instructions may also be stored in a non-transitory computer usable or computer-readable memory that may direct a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer usable or computer-readable memory produce an article of manufacture including instruction means that perform the function specified in the flowchart block(s). The computer program instructions may also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable data processing apparatus to produce a computer executed process such that the instructions that perform on the computer or other programmable data processing apparatus provide steps for executing the functions specified in the flowchart block(s).

[0037] Further, each block may represent a module, segment, or portion of code, which includes one or more executable instructions for executing the specified logical function(s). It should also be noted that in some alternative implementations, the functions noted in the blocks may occur out of the order. For example, two blocks(or functions) shown in succession may in fact be performed substantially concurrently or the blocks may sometimes be performed in the reverse order, depending upon the functionality involved.

[0038] As used in embodiments of the disclosure, a "~unit / module" may refer to a software element or a hardware element, such as a field programmable gate array (FPGA) or an application specific integrated circuit (ASIC), which performs a predetermined function. However, the term including the word "~unit / module" does not always have a meaning limited to software or hardware. The "~unit / module" may be constructed either to be stored in an addressable storage medium or to execute one or more processors. Therefore, the "~unit / module" includes, for example, software elements, object-oriented software elements, components such as class elements and task elements, processes, functions, properties, procedures, sub-routines, segments of a program code, drivers, firmware, micro-codes, circuits, data, database, data structures, tables, arrays, and parameters. The components and functions provided by the "~unit / module" may be either combined into a smaller number of components and a "~unit / module," or divided into additional components and a "~unit / module." Moreover, the components and "~units / modules" may be implemented to reproduce one or more central processing units (CPUs) within a device or a security multimedia card. Further, in the embodiments, the "unit / module" may include one or more processors.

[0039] The entirety of the one or more computer programs may be stored in a single memory device or the one or more computer programs may be divided with different portions stored in different multiple memory devices.

[0040] Any of the functions or operations described herein can be processed by one processor or a combination of processors. The one processor or the combination of processors is circuitry performing processing and includes circuitry like an application processor (AP, e.g. a CPU), a communication processor (CP, e.g., a modem), a graphics processing unit (GPU), a neural processing unit (NPU) (e.g., an artificial intelligence (AI) chip), a Wi-Fi chip, a Bluetooth® chip, a global positioning system (GPS) chip, a near field communication (NFC) chip, connectivity chips, a sensor controller, a touch controller, a finger-print sensor controller, a display driver integrated circuit (IC), an audio CODEC chip, a universal serial bus (USB) controller, a camera controller, an image processing IC, microprocessors, microcontrollers, digital　signal processors, FPGA, ASIC, a microprocessor unit (MPU), a system on chip (SoC), an IC, or the like. The one processor or the combination of processors executes instructions that can be stored in a memory, such as the　operating system, in order to control the overall operation of the device.　Also, the one processor or the combination of processors is also capable of executing other processes and programs　resident in the memory, such as processes for the disclosure.

[0041] It will be appreciated that various embodiments of the disclosure according to the claims and description in the specification can be realized in the form of hardware, software or a combination of hardware and software.

[0042] Any such software may be stored in non-transitory computer readable storage media. The non-transitory computer readable storage media store one or more computer programs (software modules), the one or more computer programs include computer-executable instructions that, when executed by one or more processors of an electronic device individually or collectively, cause the electronic device to perform a method of the disclosure. Additionally, or alternatively, such software may be a computer program [product] comprising instructions which, when executed by one or more processors of an electronic device individually or collectively, cause the electronic device to perform a method of the disclosure.

[0043] Any such software may be stored in the form of volatile or non-volatile storage such as, for example, a storage device like read only memory (ROM), whether erasable or rewritable or not, or in the form of memory such as, for example, random access memory (RAM), memory chips, device or integrated circuits or on an optically or magnetically readable medium such as, for example, a compact disk (CD), digital versatile disc (DVD), magnetic disk or magnetic tape or the like. It will be appreciated that the storage devices and storage media are various embodiments of non-transitory machine-readable storage that are suitable for storing a computer program or computer programs comprising instructions that, when executed, implement various embodiments of the disclosure. Accordingly, various embodiments of the present disclosure may provide a program comprising code for implementing apparatus or a method as claimed in any one of the claims of this specification and a non-transitory machine-readable storage storing such a program.

[0044] Hereinafter, the determination of priority between A and B in the present disclosure may refer to various actions such as selecting the one having a higher priority based on a predefined priority rule and performing an operation corresponding thereto, or omitting or dropping an operation corresponding to the one having a lower priority.

[0045] Hereinafter, "A or B" as described in the present disclosure may be understood as "A and / or B," which may include A, or B, or both A and B.

[0046] In addition, "at least one of A, B, and C" as described in the present disclosure may be understood to include A, or B, or C, or any combination of A, B, and C.

[0047] In addition, "at least one of A, B, or C" as described in the present disclosure may be understood to include A, or B, or C, or any combination of A, B, and C.

[0048] Furthermore, "A / B" as described in the present disclosure may be understood as "A and / or B," which may include A, or B, or both A and B.

[0049] Furthermore, "A, B" as described in the present disclosure may be understood as "A and / or B," which may include A, or B, or both A and B.

[0050] Furthermore, "A and B" as described in the present disclosure may be understood as "A and / or B," which may include A, or B, or both A and B.

[0051] Furthermore, "if condition A and condition B are satisfied," as described in the present disclosure, may not be limited to a case where both condition A and condition B are satisfied, but may be understood to include a case where either condition A or condition B is individually satisfied, both condition A and condition B are satisfied, or one or more additional conditions are satisfied in combination.

[0052] Furthermore, throughout this disclosure, ordinal terms such as "first," "second," "third," etc., (and similar qualifiers) are used merely to distinguish between different instances, occurrences, configurations, messages, stages, elements or aspects of elements, operations, or information as described herein. Unless the context clearly dictates otherwise, the use of such ordinal terms does not itself require that the elements, operations, or information distinguished by these terms be structurally different, numerically distinct, or substantively dissimilar. For example, a "first signal" and a "second signal" may refer to instances of the same signal transmitted at different times or containing the same core information despite minor variations, or they may refer to signals with different content or characteristics, depending on the specific context. Similarly, a "first value" and a "second value" may represent the same magnitude but measured or applied in different circumstances, or they may represent different magnitudes. The interpretation should be guided by the specific technical context, function, and relationship described in the relevant portion of the specification and claims.

[0053] Furthermore, the terms "first ~", "second ~", etc., as described in the present disclosure with respect to various elements (e.g., information, objects, operation, sequences, or the like), should not limit those elements. These terms may only be intended to distinguish one element from another, and may not be intended to indicate a specific order. For example, a first element could be termed a second element, and, similarly, a second element could be termed a first element.

[0054] Furthermore, even if "first ~" and "second ~" are described in the present disclosure, it may be understood that element(s) referred to by "first ~" and "second ~" may be the same or different. For example, in case of element(s) being information, first information and second information may both be same information and, in some cases, are separate and different information.

[0055] In addition, the terms "if ~" and "in case that ~" as used in the disclosure or claims may be interpreted to include the meanings of "when (or upon) ~," "in response to ~," "based on ~," or "according to ~," and may be used interchangeably with these expressions. In addition, expressions other than those exemplified herein may also be used, as long as they have substantially the same meaning and do not impair the technical features of the present disclosure. If a method step (e.g. transmit a signal) is performed according to the disclosure of the application in connection with one of the above terms (such as "in case that ~" or the like), it may be interpreted to include the meanings (disclosure) of a prior determination that a feature has a specific state "~" (e.g. a bit length is above X), and then perform the method step in response to said determination.

[0056] For example, the physical layer signaling may be referred to as Layer 1 (L1) signaling and may include downlink control information (DCI). In addition, the higher layer signaling may include a medium access control (MAC) control message, a radio resource control (RRC) signaling message, a non-access stratum (NAS) signaling message, or an application layer message. The RRC signaling message may be referred to as L3 (layer 3) signaling. It should be noted, however, that the higher layer signaling is not limited to the aforementioned examples.

[0057] In addition, the term "not perform" as used in the present disclosure or claims may, in context, be understood to mean that the corresponding step is omitted or skipped. Such a term may be replaced with other terms having the same or substantially equivalent meaning.

[0058] In addition, "transmitting a message including A and B" as described in the present disclosure, may be understood as encompassing both (i) transmitting A and B in a single message, and (ii) transmitting A and B separately via multiple messages (e.g., transmitting a first message including A and a second message including B). This interpretation may also apply to messages that include two or more items (e.g., A, B, C), transmitted either together or separately.

[0059] In addition, "transmitting a message including A and transmitting a message including B" may also be interpreted as transmitting a message including A and B in a single message.

[0060] In the embodiments of the present disclosure described herein, terms or components included in the disclosure may be expressed in singular or plural form depending on the specific embodiments presented. However, such singular or plural expressions are selected appropriately for convenience of description, and the present disclosure is not limited to a singular or plural number of components. A component expressed in the plural form may be implemented as a single component, and a component expressed in the singular form may be implemented as multiple components.

[0061] The drawings or flowcharts described herein illustrate example methods that may be implemented according to the principles of the present disclosure, and various modifications may be made to the methods illustrated in the flowcharts of the present disclosure. For example, although illustrated as a series of steps, various steps in each drawing or flowchart may overlap, occur in parallel, occur in a different order, or be repeated. In other examples, any step may be omitted or replaced with another step.

[0062] The process of the flowchart may be performed by a device. One or more of the steps of the　flowchart can be implemented by one or more processors / computer programs executing　instructions to perform the noted functions.

[0063] The methods and apparatuses proposed in the embodiments of the present disclosure may be disclosed in connection with drawings disclosing flowcharts to illustrate example methods that may be implemented according to the principles of the present disclosure. Such flowcharts may contain different branches and / or sub-branches. It is understood that the principles of the present disclosure do not only contain the combination of all branches / sub-branches disclosed in the embodiment, but the present disclosure also contains at least one isolated branch / isolated sub-branch, in particular to a single branch / single sub-branch.

[0064] The methods and apparatuses proposed in the embodiments of the present disclosure are not limited to each embodiment individually, but may also be applied in combination of all or some of the embodiments proposed in the disclosure. Therefore, the embodiments of the present disclosure may be modified and applied without significantly departing from the scope of the present disclosure, as would be understood by those skilled in the art.

[0065] In this case, even if certain wordings are described differently across embodiments, they may be used interchangeably or in substitution or in combination if their underlying concepts are equivalent. For example, for the same or equivalent concept, even if one embodiment uses the expression "A" and another embodiment uses the expression "B", such expressions may be understood interchangeably, in substitution, or in combination.

[0066] The terms used in the following description to refer to access nodes, network entities, messages, interfaces between network entities, various types of identification information, and the like, are provided merely for the convenience of explanation by way of example. Therefore, the present disclosure is not limited to the terms describedherein, and other terms having equivalent technical meanings may also be used. Such terms may also be interchangeable with terms defined in any 3rd generation partnership project　(3GPP) technical specifications (TS) or similar technical specifications, e.g., from the European telecommunications standards institute (ETSI), where appropriate.

[0067] Hereinafter, a base station (BS) is an entity that allocates resources to terminals, and may be at least one of a gNode B, an eNode B, a Node B, a wireless access unit, a BS controller, or a node on a network.

[0068] Furthermore, the base station of the present disclosure may include a split architecture comprising a central unit (CU) and a distributed unit (DU). In this structure, the CU is configured to process the higher layers of the control and user planes, while the DU is configured to process lower-layer radio resource functions. The embodiments of the present disclosure may be equally applicable to 5th generation (5G) base station architectures in which such CU and DU functional splits are implemented.

[0069] A terminal may include a user equipment (UE), a mobile station (MS), a cellular phone, a smartphone, a computer, a tablet, a wearable device, an Internet of Things (IoT) device, or any other device / system capable of performing communication functions.

[0070] In the disclosure, a downlink (DL) refers to a radio link through which a BS transmits a signal to a terminal, and an uplink (UL) refers to a radio link through which a terminal transmits a signal to a BS.

[0071] Furthermore, hereinafter, 5G mobile communication technologies (e.g., 5G new radio (NR)), 6th generation (6G) mobile communication technologies may be described by way of example, but the embodiments of the present disclosure may also be applied to other communication systems having similar technical backgrounds or channel types. For example, newly evolved mobile communication systems developed after 5G and 6G may be included. Furthermore, based on determinations by those skilled in the art, the embodiments of the present disclosure may also be applied to other communication systems (e.g., Wi-Fi systems) through some modifications without significantly departing from the scope of the present disclosure

[0072] In the following description, the terms physical channel and signal may be used interchangeably with data or control signal. For example, the term physical downlink shared channel (PDSCH) refers to a physical channel through which data is transmitted, but the term PDSCH may also be used to refer to the data itself. That is, in the present disclosure, the expression "transmit a physical channel" may be interpreted as being equivalent to the expression "transmit data or a signal via a physical channel."

[0073] Hereinafter, in the context of the present disclosure, higher layer signaling may refer to signaling corresponding to at least one or any combination of the following: master information block (MIB), system information block (SIB) or SIB M (M = 1, 2, ...), RRC, or MAC control element (CE), or a non-access stratum (NAS) signaling message, or an application layer message. The RRC signaling message may be referred to as Layer 3 (L3) signaling.

[0074] In addition, L1 signaling may refer to signaling corresponding to at least one or any combination of signaling techniques using the at least one or any combination of the following physical layer channels or signaling: physical downlink control channel (PDCCH), DCI, UE-specific DCI, group-common DCI, common DCI, scheduling DCI (e.g., DCI used for scheduling downlink or uplink data), non-scheduling DCI (e.g., DCI not used for scheduling downlink or uplink data) physical uplink control channel (PUCCH), or uplink control information (UCI). The L1 signaling message may be referred to as a physical layer signaling.

[0075] Hereinafter, the expression that information is configured by the BS, as used in the present disclosure or claims, may, in context, be understood to mean that the terminal receives the corresponding information from the BS via a physical layer signaling or a higher layer signaling. Such an expression may be replaced with other terms having the same or substantially equivalent meaning.

[0076] Hereinafter, the operational principle of the present disclosure will be described in detail with reference to the accompanying drawings.

[0077] The User Equipment (UE) and the network may support Minimization of Service Interruption (MINT). MINT aims to enable a UE to obtain service from a Public Land Mobile Network (PLMN) offering disaster roaming services when a disaster condition applies to the UE-determined PLMN with a disaster condition.

[0078] Upon selecting a PLMN for disaster roaming as specified in Third Generation Partnership Project (3GPP) TS 23.122 [5], a) if the UE does not have a stored disaster roaming wait range, the UE shall perform a registration procedure for disaster roaming services on the selected PLMN as described in subclause 5.5.1, and b) if the UE has a stored disaster roaming wait range, the UE shall generate a random number within the disaster roaming wait range and start a timer with the generated random number. While the timer is running, the UE shall not initiate registration on the selected PLMN. Upon expiration of the timer, if the UE does not have an emergency PDU session, the UE shall perform a registration procedure for disaster roaming services if still camped on the selected PLMN.

[0079] Upon determining that a disaster condition has ended as specified in 3GPP TS 23.122 [6]: a) the UE shall stop the timer started with a generated random number within the disaster roaming wait range, if running; b) the UE shall perform PLMN selection as specified in 3GPP TS 23.122 [5], except if the UE already selected an allowable PLMN as specified in 3GPP TS 23.122 [6]; and c) if the UE selects the UE determined PLMN with disaster condition and has a stored disaster return wait range, which is 1) provided by the PLMN providing disaster roaming services; or 2) provided by the selected PLMN.

[0080] The UE shall generate a random number within the disaster return wait range, start a timer with the generated random number value and enter 5GMM-DEREGISTERED.ATTEMPTING-REGISTRATION state or 5GMM-REGISTERED.ATTEMPTING-REGISTRATION-UPDATE state, if registered. While the timer is running, the UE shall not initiate registration on the selected PLMN, except if the UE needs to request the emergency PDU session. Upon expiration of the timer, if the UE does not have the emergency PDU session, the UE shall perform a registration procedure if still camped on the selected PLMN.

[0081] If the UE has already run the disaster roaming wait range timer or disaster return wait range timer at least once or the timer for disaster return wait range or timer for disaster roaming wait range has expired, optionally for the previously selected PLMN, and the UE selects or needs to select a PLMN, optionally same or different PLMN from the previously selected PLMN, after PLMN selection procedure as specified in 3GPP TS 23.122, the UE has to start or run the timer for disaster roaming wait range or the timer for disaster return wait range for the selected PLMN before triggering a procedure on the selected PLMN. This would lead to delay in getting the desired service for the UE.

[0082] Thus, it is desired to address the above mentioned disadvantages or other shortcomings or at least provide a useful alternative.

[0083] The embodiments and their features are explained with reference to the non-limiting examples in the accompanying drawings and description. Well-known components and techniques are omitted to avoid unnecessary detail. Embodiments can be combined to form new ones. The term "or" is non-exclusive unless stated otherwise. The examples provided are for understanding and enabling practice of the embodiments and should not limit their scope.

[0084] Embodiments may be described and illustrated as blocks performing specific functions. These blocks, referred to as managers, units, modules, or hardware components, are implemented using analog and / or digital circuits, such as logic gates, integrated circuits, microprocessors, memory circuits, and optical components, possibly driven by firmware and software. These circuits can be on semiconductor chips or substrates like printed circuit boards. Blocks can be implemented with dedicated hardware, processors, or a combination of both. Each block can be divided into separate interacting blocks or combined into more complex blocks without departing from the disclosure's scope.

[0085] Throughout the specification, the definitions of the various terms used in the embodiments are as follows:

[0086] Satellite: An artificial body placed in orbit round the earth or moon or another planet in order to collect information or for communication.

[0087] Satellite Constellation: Group of satellites, placed in orbit round the earth or moon or another planet in order to collect information or for communication.

[0088] Service User: An individual who has received a priority level assignment from a regional / national authority (i.e., an agency authorized to issue priority assignments) and has a subscription to a mobile network operator.

[0089] Visited PLMN (VPLMN):This is a PLMN different from the HPLMN (if the Equivalent Home Public Land Mobile Network (EHPLMN) list is not present or is empty) or different from an EHPLMN (if the EHPLMN list is present).

[0090] Allowable PLMN:In the case of an MS operating in MS operation mode A or B, this is a PLMN which is not in the list of "forbidden PLMNs" in the MS. In the case of an MS operating in MS operation mode C or an MS not supporting A / Gb mode and not supporting Iu mode, this is a PLMN which is not in the list of "forbidden PLMNs" and not in the list of "forbidden PLMNs for General Packet Radio Service (GPRS) service" in the MS.

[0091] Available PLMN: PLMN(s) in the given area which is / are broadcasting capability to provide wireless communication services to the UE.

[0092] Camped on a cell:The MS (ME if there is no Subscriber Identity Module (SIM)) has completed the cell selection / reselection process and has chosen a cell from which it plans to receive all available services. Note that the services may be limited, and that the PLMN or the Standalone Non-Public Networks (SNPN) may not be aware of the existence of the MS (ME) within the chosen cell.

[0093] EHPLMN: Any of the PLMN entries contained in the Equivalent HPLMN list.

[0094] Equivalent HPLMN list: To allow provision for multiple HPLMN codes, PLMN codes that are present within this list shall replace the HPLMN code derived from the IMSI for PLMN selection purposes. This list is stored on the Universal Subscriber Identification Module (USIM) and is known as the EHPLMN list. The EHPLMN list may also contain the HPLMN code derived from the IMSI. If the HPLMN code derived from the IMSI is not present in the EHPLMN list then it shall be treated as a Visited PLMN for PLMN selection purposes.

[0095] Home PLMN: This is a PLMN where the Mobile Country Code (MCC) and Mobile Network Code (MNC) of the PLMN identity match the MCC and MNC of the IMSI.

[0096] Registered PLMN (RPLMN):This is the PLMN on which certain LR (location registration which is also called as registration procedure) outcomes have occurred. In a shared network the RPLMN is the PLMN defined by the PLMN identity of the CN operator that has accepted the LR.

[0097] Registration: This is the process of camping on a cell of the PLMN or the SNPN and doing any necessary LRs.

[0098] UPLMN: PLMN / access technology combination in the "User Controlled PLMN Selector with Access Technology" data file in the SIM (in priority order);

[0099] OPLMN: PLMN / access technology combination in the "Operator Controlled PLMN Selector with Access Technology" data file in the SIM (in priority order) or stored in the ME (in priority order).

[0100] Disaster Condition: This is the condition that a government decides when to initiate and terminate, example, a natural disaster. When this condition applies, users may have the opportunity to mitigate service interruptions and failures.

[0101] Disaster Inbound Roamer: A user that (a) cannot get service from the PLMN it would normally be served by, due to failure of service during a Disaster Condition, and (b) is able to register with other PLMNs.

[0102] Disaster Roaming: This is the special roaming policy that applies during a Disaster Condition.

[0103] PLMN with Disaster Condition: A PLMN to which a Disaster Condition applies.

[0104] Registered for disaster roaming services: A UE is considered as "registered for disaster roaming services" when it has successfully completed initial registration or mobility registration for disaster roaming services.

[0105] The following are examples of Non-Access Stratum (NAS) messages, including but not limited to: REGISTRATION REQUEST message, DEREGISTRATION REQUEST message, SERVICE REQUEST message, CONTROL PLANE SERVICE REQUEST, IDENTITY REQUEST, AUTHENTICATION REQUEST, AUTHENTICATION RESULT, AUTHENTICATION REJECT, REGISTRATION REJECT, REGISTRATION ACCEPT, DEREGISTRATION ACCEPT, SERVICE REJECT, SERVICE ACCEPT, UE CONFIGURATION UPDATE command, and UE PARAMETERS UPDATE command.

[0106] In an embodiment, 5GS registration types include Initial registration, Mobility registration updating, Periodic registration updating, Emergency registration, SNPN onboarding registration, "Disaster roaming initial registration," or "Disaster roaming mobility registration updating."

[0107] Setting the registration type to a value other than "disaster roaming initial registration" or "disaster roaming mobility registration updating" means that the 5GS registration type is set to at least one of the following: Initial registration, Mobility registration updating, Periodic registration updating, Emergency registration, and SNPN onboarding registration.

[0108] The following discloses Public Land Mobile Network (PLMN) selection as per 23.122 without Registered Public Land Mobile Network (RPLMN):

[0109] The MS selects and attempts registration on any PLMN / access technology combinations if available and allowable in the following order: a) either the HPLMN (if the EHPLMN list is not present or is empty) or the highest priority EHPLMN that is available (if the EHPLMN list is present); b) each PLMN / access technology combination in the "User Controlled PLMN Selector with Access Technology" data file in the SIM (in priority order); c) each PLMN / access technology combination in the "Operator Controlled PLMN Selector with Access Technology" data file in the SIM (in priority order) or stored in the ME (in priority order); d) other PLMN / access technology combinations with received high-quality signal in random order; and e) other PLMN / access technology combinations in order of decreasing signal quality.

[0110] The following discloses PLMN selection as per 23.122 with RPLMN:

[0111] The MS selects and attempts registration on any PLMN / access technology combinations if available and allowable in the following order: a) either the RPLMN or the last registered PLMN, b) either the HPLMN (if the EHPLMN list is not present or is empty) or the highest priority EHPLMN that is available (if the EHPLMN list is present), c) each PLMN / access technology combination in the "User Controlled PLMN Selector with Access Technology" data file in the SIM (in priority order), d) each PLMN / access technology combination in the "Operator Controlled PLMN Selector with Access Technology" data file in the SIM (in priority order) or stored in the ME (in priority order), e) other PLMN / access technology combinations with received high-quality signal in random order, and f) other PLMN / access technology combinations in order of decreasing signal quality.

[0112] The purpose of MINT is to minimize interruption of service to users when the network to which these users are subscribed cannot provide service due to a disaster, such as, e.g., a fire, by enabling the users to obtain service on other networks while at the same time protecting those other networks from congestion.

[0113] In the description, the PLMN D or PLMN-D is subject to disaster (i.e., PLMN-D is the PLMN with disaster condition) and PLMN A or PLMN-A is alive and not subject to disaster. PLMN-A may provide disaster roaming service to the users of the PLMN-D (i.e., to the Disaster Inbound roamers of the PLMN-D).

[0114] The terms disaster-based service, disaster roaming service, and disaster inbound roaming are used interchangeably in this embodiment and have the same meaning. The terms disaster situation and disaster condition are used interchangeably in this embodiment and have the same meaning. The terms PLMN D and PLMN-D are used interchangeably in this embodiment and have the same meaning. The terms PLMN A and PLMN-A are used interchangeably in this embodiment and have the same meaning. The terms UE and MS are used interchangeably in this embodiment and have the same meaning. The term or method where UE is registering for the disaster roaming service or UE is registered for the disaster roaming service may refer to a situation or condition but not restricted or limited to where UE sets or indicates the Fifth Generation System (5GS) Registration type IE to at least one of a disaster roaming initial registration and a disaster roaming mobility registration updating in the REGISTRATION REQUEST message. The term area / location / geographical area used in this embodiment may refer to any of cell / cell ID, Tracking Area Code (TAC) / Tracking Area Identity (TAI), PLMN, MCC / MNC, Latitude / longitude, Closed access group (CAG) cell, or any geographical location / coordinate.

[0115] The solution explained in this embodiment is applicable to any (but not limited to) of the RAT(s) as defined in this embodiment.

[0116] The Network used in this embodiment could be any 5G / Evolved Universal Mobile Telecommunication Access Network (EUTRAN) Core Network Entities like Access and Mobility Management Function (AMF) / SMF / Mobility Management Entity (MME) / UPF or the Network could be any (but not limited to) 5G / EUTRAN RAN Entity like eNodeB (eNB) or gNodeB (gNB) or NG-RAN, etc.

[0117] The methods, issues, or solutions disclosed in this embodiment are explained using NR access or NG-RAN Access Technology as an example and are not restricted or limited to NR access only. However, the solutions proposed in this embodiment are also applicable for E-UTRAN access technology, NB (Narrow Band)-S1 mode, or WB (Wide Band)-S1 mode via E-UTRAN access and / or NB-IOT (NarrowBand Internet Of Things) or WB-IOT (WideBand Internet Of Things) Access / Architecture.

[0118] The solutions which are defined for NR (5GC) are also applicable to legacy RATs like E-UTRA / LTE. The corresponding CN entities need to be replaced by LTE entities, for example, AMF with MME, gnodeB with enodeB, Unified Data Management Function (UDM) with HSS, etc. But the principles of the solution remain the same.

[0119] The network used in this embodiment is explained using any 5G Core Network Function, for example, AMF. However, the network could be any 5G / EUTRAN Core Network Entities like AMF / SMF / MME / UPF, or the network could be any 5G / EUTRAN RAN Entity like eNodeB (eNB) or gNodeB (gNB) or NG-RAN, etc.

[0120] The messages used or indicated in this embodiment are shown as an example. The messages could be any signaling messages between UE and the Network Functions / Entities or between different Network functions / entities.

[0121] The terms camp and register are used interchangeably and have the same meaning. The term area as used in this embodiment may refer to any of cell / cell ID, TAC / TAI, PLMN, MCC / MNC, latitude / longitude, any CAG / CAG identifier, or any geographical location / coordinate.

[0122] For the list of possible NAS messages please refer to 3GPP TS 24.501 or 3GPP TS 24.301. For list of AS messages please refer to 3GPP TS 38.331 or 3GPP TS 36.331.

[0123] The cause names in this embodiment are for illustration purposes and can have any name. The non-access stratum (NAS) messages and access stratum (AS) messages described in this embodiment are only for illustration purposes; they can be any NAS or AS messages as per the defined protocol between UE and AMF / MME or UE and gNB (NG-RAN / any RAN node) / eNB.

[0124] The solutions defined for NR (5GC) are also applicable to legacy RATs like E-UTRA / LTE. The corresponding CN entities need to be replaced by LTE entities, for example, AMF with MME, gnodeB with enodeB, UDM with HSS, etc. But the principles of the solution remain the same.

[0125] An example list of NAS messages can be, but is not limited to, REGISTRATION REQUEST message, DEREGISTRATION REQUEST message, SERVICE REQUEST message, CONTROL PLANE SERVICE REQUEST, IDENTITY REQUEST, AUTHENTICATION REQUEST, AUTHENTICATION RESULT, AUTHENTICATION REJECT, REGISTRATION REJECT, DEREGISTRATION ACCEPT, SERVICE REJECT, SERVICE ACCEPT, and so on.

[0126] The Network used in this embodiment is explained using any 5G Core Network Function, for example, AMF. However, the network could be any 5G / EUTRAN Core Network Entities like AMF / SMF / MME / UPF, or the Network could be any 5G / EUTRAN RAN Entity like eNodeB (eNB) or gNodeB (gNB) or NG-RAN, etc.

[0127] The messages used or indicated in this embodiment are shown as an example. The messages could be any signaling messages between UE and the Network Functions / Entities or between different Network functions / entities. The terms area / location / geographical area used in this embodiment may refer to any of cell / cell ID, TAC / TAI, PLMN, MCC / MNC, Latitude / longitude, CAG cell, or any geographical location / coordinate.

[0128] The methods, issues, or solutions disclosed in this embodiment are explained using NR access or NG-RAN Access Technology as an example and are not restricted or limited to NR access only. However, the solutions proposed in this embodiment are also applicable for E-UTRAN access Technology, NB (Narrow Band)-S1 mode, or WB (Wide Band)-S1 mode via E-UTRAN access and / or NB-IOT (NarrowBand Internet Of Things) or WB-IOT (WideBand Internet Of Things) Access / Architecture.

[0129] The solution which is defined for NR (5GC) is also applicable to legacy RATs like E-UTRA / LTE. The corresponding CN entities need to be replaced by LTE entities, for example, AMF with MME, gnodeB with enodeB, UDM with HSS, etc. But the principles of the solution remain the same.

[0130] The network used in this embodiment is explained using any 5G Core Network Function, for example, AMF. However, the network could be any 5G / EUTRAN Core Network Entities like AMF / SMF / MME / UPF, or the network could be any 5G / EUTRAN RAN Entity like eNodeB (eNB) or gNodeB (gNB) or NG-RAN, etc.

[0131] The messages used or indicated in this embodiment are shown as an example. The messages could be any signaling messages between UE and the Network Functions / Entities or between different Network functions / entities.

[0132] The terms camp and register are used interchangeably and have the same meaning. The term area as used in this embodiment may refer to any of cell / cell ID, TAC / TAI, PLMN, MCC / MNC, Latitude / longitude, any CAG / CAG identifier, or any geographical location / coordinate.

[0133] The terms timer for disaster roaming wait range, disaster roaming wait range timer, disaster roaming wait timer and disaster roaming wait range duration are used interchangeably and have the same meaning.

[0134] The terms timer for disaster return wait range, disaster return wait range timer, disaster return wait timer and disaster return wait range duration are used interchangeably and have the same meaning.

[0135] For the list of possible NAS messages, please refer to 3GPP TS 24.501 or 3GPP TS 24.301. For the list of AS messages, please refer to 3GPP TS 38.331 or 3GPP TS 36.331.

[0136] The cause names in this embodiment are for illustration purposes and can have any name. The non-access stratum (NAS) messages and access stratum (AS) messages described in this embodiment are only for illustration purposes. They can be any NAS or AS messages as per the defined protocol between UE and AMF / MME or UE and gNB (NG-RAN / any RAN node) / eNB.

[0137] Embodiments disclosed herein provide a method and system for MINT wait timer handling. In an embodiment, when a disaster condition occurs on a first PLMN (for example, UE determined PLMN with disaster condition is first PLMN), UE performs PLMN selection as specified in 3GPP TS 23.122 and selects PLMN (for example, second PLMN) or any forbidden PLMN providing disaster roaming services. UE starts a timer generated from the disaster roaming wait range optionally provided by the UE determined PLMN with disaster condition (for example, first PLMN) or provided by the selected PLMN (for example, second PLMN) or the Home PLMN (HPLMN). UE waits for the disaster roaming wait range duration. After the UE has waited for the disaster roaming wait range duration, UE registers on the second PLMN for disaster roaming services. The UE receives a registration reject from the second PLMN or the registration is not successful on the second PLMN due to any reasons. The UE performs PLMN selection as specified in 3GPP TS 23.122 and selects another PLMN (for example, third PLMN) or any forbidden PLMN providing disaster roaming services. In an embodiment, the UE may select the second PLMN again or any PLMN for disaster roaming services. Upon selecting a PLMN for disaster roaming as specified in 3GPP TS 23.122, if the timer for disaster roaming wait range has expired at least once, the UE shall not use the disaster roaming wait range value again upon selecting a PLMN for disaster roaming services after PLMN selection as specified in 3GPP TS 23.122. Without waiting for the disaster roaming wait range duration again, UE shall immediately perform the registration procedure in the selected PLMN (for example, third PLMN) for disaster roaming services. Upon expiry of the timer for disaster return wait range, the UE shall not start a timer with the disaster return wait range value again until the UE selects a PLMN for disaster roaming services.

[0138] In an embodiment, when a disaster condition occurs on the second PLMN (for example, UE determined PLMN with disaster condition is the second PLMN), the UE is registered to the first PLMN for disaster roaming services. The disaster condition ends on the second PLMN. Upon determining that a disaster condition has ended as specified in 3GPP TS 23.122, the UE performs PLMN selection and selects UE determined PLMN with disaster condition (for example, the second PLMN) or any allowable PLMN for normal services. UE starts a timer generated from the disaster return wait range optionally provided by the PLMN providing disaster roaming services (for example, first PLMN) or provided by the selected PLMN (for example, second PLMN). The UE waits for the disaster return wait range duration. After the UE has waited for the disaster return wait range duration, the UE registers on the second PLMN for normal services. The UE receives a registration reject from the second PLMN or the registration is not successful on second PLMN due to any reasons. The UE performs PLMN selection as specified in 3GPP TS 23.122 and selects same or another allowable PLMN (for example, third PLMN) for normal services. In an embodiment, the UE may select the second PLMN again for normal services. Upon determining that a disaster condition has ended as specified in 3GPP TS 23.122, if the timer for disaster return wait range has expired at least once, the UE shall not use the disaster return wait range value again upon selecting a PLMN after PLMN selection. Without waiting for the disaster return wait range duration again, the UE shall immediately perform the registration procedure in the selected PLMN (for example, third PLMN) for normal services. Upon expiry of the timer for disaster return wait range, the UE shall not start a timer with the disaster return wait range value again until the UE selects a PLMN for disaster roaming services.

[0139] The present disclosure provides a method and system for handling a MINT (Minimization of service interruption) wait timer. The disclosure proposes two solutions for addressing existing mechanisms. In an embodiment, upon selecting a PLMN for disaster roaming, if the UE receives a REGISTRATION REJECT message while registering for disaster roaming services in the selected PLMN, the UE shall not use the disaster roaming wait range value again upon selecting a PLMN after PLMN selection. In an embodiment, upon determining that a disaster condition has ended, if the UE receives a REGISTRATION REJECT message while registering for normal services in the MS-determined PLMN with the disaster condition, the UE shall not use the disaster return wait range value again upon selecting a PLMN after PLMN selection.

[0140] Referring now to the drawings, and more particularly to FIGS. 1b, 2b, 3 and 4, where similar reference characters denote corresponding features throughout the figures, there are shown preferred embodiments.

[0141] FIG. 1A is a sequence diagram that illustrates the existing method where a UE (102) runs and waits for the timer for disaster roaming wait range to expire even when the UE (102) has already waited once for the disaster roaming wait range duration or the timer for disaster roaming wait range has already expired once, optionally after the disaster condition has occurred according to prior art.

[0142] Upon selecting a PLMN for disaster roaming as specified in 3GPP TS 23.122: a) if the UE (102) does not have a stored disaster roaming wait range, the UE (102) shall perform a registration procedure for disaster roaming services on the selected PLMN as described in subclause 5.5.1; and b) if the UE (102) has a stored disaster roaming wait range, the UE (102) shall generate a random number within the disaster roaming wait range and start a timer with the generated random number. While the timer is running, the UE (102) shall not initiate registration on the selected PLMN except if the UE (102) needs to request an emergency PDU session, in which case the UE shall initiate the registration procedure, set the 5GS registration type IE to "emergency registration" in the REGISTRATION REQUEST message, and keep the timer running. Upon expiration of the timer, if the UE (102) does not have the emergency PDU session, the UE (102) shall perform a registration procedure for disaster roaming services as described in subclause 5.5.1 if still camped on the selected PLMN. If the UE (102) has the emergency PDU session when the timer expires, the registration procedure for disaster roaming services as described in subclause 5.5.1 shall be performed after the release of the emergency PDU session if the UE (102) is still camped on the selected PLMN.

[0143] The UE (102) is registered / camped to PLMN-D1 for normal services. The UE (102) was configured with Disaster Roaming Wait Range for the PLMN(s) providing disaster roaming service (for example, PLMN-A1, PLMN-A2, PLMN-A3, etc.) and Disaster Return Wait Range optionally by the PLMN-D1 or the registered PLMN or the Home PLMN (HPLMN) of the UE (102).

[0144] The disaster condition occurs, and the UE (102) determines the disaster condition is met. Upon selecting a PLMN (for example, a PLMN-A1 which is not an allowable PLMN for the UE (102) and is a Forbidden PLMN for the UE (102)) for disaster roaming, if there is a disaster roaming wait range stored in the ME / UE (102) optionally for PLMN-A1, the MS / UE (102) shall generate a random number within the disaster roaming wait range and start a timer set to the generated random number. While the timer is running, the MS shall not initiate registration with the exception of performing an initial registration for emergency services in the selected PLMN (i.e., PLMN-A1).

[0145] However, there may be situations where after the UE (102) has waited for the timer generated from the disaster roaming wait range (for example, disaster roaming wait range duration) before registering on the selected PLMN (PLMN-A1), the UE (102) may have to perform PLMN selection again to select same or another PLMN (for example, PLMN-A2) for disaster roaming services (for example, the UE (102) may have to select another PLMN (for example, PLMN-A2 which is not an allowable PLMN for the UE (102) and is a Forbidden PLMN for the UE (102)) for disaster roaming services). Some examples of the situations (but not restricted to these examples) are a) when the UE (102) gets a registration reject or any reject cause on the first selected PLMN (i.e., PLMN-A1) and selects another PLMN (i.e., PLMN-A2) or b) when the UE (102) faces Out-of-service (OOS) or Radio-Link-Failure (RLF) or No-Service or lack of coverage on one PLMN and moves to another PLMN or c) when the UE (102) loses the services of the first selected PLMN (for example, PLMN-A1) and selects / camps on another selected PLMN (for example, PLMN-A2) or d) when the first selected PLMN (for example, PLMN-A2) faces disaster condition and the UE (102) selects another PLMN (for example, PLMN-A2), etc.

[0146] Similarly, there may be situations, for example, a) when the UE (102) may select / move from the first selected PLMN (i.e., PLMN-A1) to another selected PLMN (for example, PLMN-A2) for disaster roaming service and may select the first PLMN (i.e., PLMN-A1) again (for example, PLMN-A1 to PLMN-A2 to PLMN-A1) or b) when the UE (102) may select the first selected PLMN (for example, PLMN-A1), start a timer with a generated random number within the disaster roaming wait range, and on expiry of the timer, the UE (102) is not able to find coverage of the selected PLMN. After some time, the UE (102) selects the same PLMN (for example, PLMN-A1) again.

[0147] In an embodiment, there may be a situation where if the timer for disaster roaming wait range has expired once or once the UE (102) has waited for the disaster roaming wait range duration optionally before registering on the selected forbidden PLMN (FPLMN) (for example, PLMN-A1), the UE (102) attempts registration on the selected PLMN (FPLMN) for disaster roaming services, and the registration is rejected or the registration is not successful. The UE (102) may perform PLMN Selection again to select another PLMN (for e.g. PLMN-A2) or forbidden PLMN for disaster roaming services.

[0148] In these situations, if there is a disaster roaming wait range stored in the ME / UE (102) optionally for the selected PLMN (for example, PLMN-A1 or PLMN-A2), the UE (102) shall generate a random number within the disaster roaming wait range and start a timer (for example, disaster roaming wait timer) set to the generated random number. While the timer is running, the MS shall not initiate registration with the exception of performing an initial registration for emergency services in the selected PLMN (i.e., PLMN-A1 or PLMN-A2). The UE (102) shall start a timer every time the UE (102) selects a PLMN for disaster roaming services. For example, the UE (102) shall start a timer (for example, disaster roaming wait timer) for the first selected PLMN (for example, PLMN-A1). if the UE (102) selects another PLMN (for example, PLMN-A2) or if the UE (102) selects the same PLMN (for example, PLMN-A1) again, the UE (102) shall again start a timer (for example, disaster roaming wait timer) for the selected PLMN (for example, PLMN-A1 or PLMN-A2).

[0149] However, the UE (102) has already started or run the disaster roaming wait range timer once or the timer for disaster roaming wait range has expired once, optionally for the previously selected PLMN or selected forbidden PLMN (FPLMN) (for example, PLMN-A1). If the UE (102) shall start / run the disaster roaming wait range timer for current selected PLMN (for e.g. PLMN-A2) or any other PLMN(s) providing disaster roaming services to the UE (102) again optionally before triggering registration on the selected PLMN, it may lead to a delay in the disaster roaming service for the UE. Currently, there is no way for the UE (102) to handle this situation, and a method needs to be defined.

[0150] As illustrated in FIG 1A, at step 1, a disaster condition occurs on the first PLMN (104a) (for example, the UE (102) determined PLMN with disaster condition is the first PLMN (104a)). At step 2, the UE (102) performs PLMN selection as specified in 3GPP TS 23.122 and selects PLMN (for example, second PLMN (104b)) or any forbidden PLMN providing disaster roaming services. The UE (102) starts a timer generated from the disaster roaming wait range optionally provided by the UE (102) determined PLMN with disaster condition (for example, the first PLMN (104a)) or provided by the selected PLMN (for example, second PLMN) or the Home PLMN (HPLMN). The UE (102) waits for the disaster roaming wait range duration. At step 3, after the UE (102) has waited for the disaster roaming wait range duration and upon expiry of the timer for disaster roaming wait range, the UE (102) registers on the second PLMN (104b) for disaster roaming services. At step 4, the UE (102) receives a registration reject from the second PLMN (104b) or the registration is not successful on the second PLMN (104b). At step 5, the UE (102) performs PLMN selection as specified in 3GPP TS 23.122 and selects another PLMN (for example, third PLMN (104c)) or any forbidden PLMN providing disaster roaming services. In an embodiment, the UE (102) may select the second PLMN (104b) again for disaster roaming services. At step 6, the UE (102) again runs / starts a timer value set to a random number within the disaster roaming wait range and the UE (102) waits for the timer (for example, disaster roaming wait range duration) to expire to perform registration on the selected PLMN (for example, third PLMN (104c)). At step 7, after the UE (102) has waited for the disaster roaming wait range duration, the UE (102) registers on the third PLMN (104c) for disaster roaming services. At step 6, the UE (102) runs and waits for the disaster roaming wait range duration even when the UE (102) has already waited once for the disaster roaming wait range duration, optionally after the disaster condition has occurred. This leads to a delay in getting disaster roaming services for the UE (102).

[0151] FIG. 1B is a sequence diagram that illustrates the proposed method whereupon expiry of the timer for disaster roaming wait range, the UE shall not start a timer with the disaster roaming wait range value again until disaster condition has ended, according to embodiments as disclosed herein.

[0152] In an embodiment, at step 1, a disaster condition occurs on the first PLMN (104a) (for example, UE (102) determined PLMN with disaster condition is the first PLMN (104a)). At step 2, the UE (102) performs PLMN selection as specified in 3GPP TS 23.122 and selects PLMN (for example, the second PLMN (104b)) or any forbidden PLMN providing disaster roaming services. The UE (102) starts a timer generated from the disaster roaming wait range optionally provided by the UE (102) determined PLMN with disaster condition (for example, the first PLMN (104a)) or provided by the selected PLMN (for example, the second PLMN (104b)) or the Home PLMN (HPLMN). The UE (102) waits for the disaster roaming wait range duration. At step 3, after the UE (102) has waited for the disaster roaming wait range duration or upon the expiry of the timer for disaster roaming wait range, the UE (102) registers on the second PLMN (104b) for disaster roaming services. At step 4, the UE (102) receives a registration reject from the second PLMN (104b) or the registration is not successful on the second PLMN (104b) due to any reasons. At step 5, the UE (102) performs PLMN selection as specified in 3GPP TS 23.122 and selects same PLMN (104b) or another PLMN (for example, third PLMN (104c)) or any forbidden PLMN providing disaster roaming services. In an embodiment, the UE (102) may select the second PLMN (104b) again for disaster roaming services. At step 6, upon expiry of the timer for disaster roaming wait range, the UE (102) shall not use the disaster roaming wait range value again upon selecting a PLMN for disaster roaming services after PLMN selection. Upon expiry of the timer for disaster roaming wait range, the UE shall not start a timer with the disaster roaming wait range value again until disaster condition has ended. At step 7, without waiting for the disaster roaming wait range duration again or without running a timer for the disaster roaming wait range again, the UE (102) shall immediately perform the registration procedure in the selected PLMN (for example, third PLMN (104c)) for disaster roaming services.

[0153] The UE (102) shall perform the below steps in any order or combinations.

[0154] In an embodiment, upon selecting a PLMN for disaster roaming as specified in 3GPP TS 23.122: a) if the UE (102) does not have a stored disaster roaming wait range, the UE (102) shall perform a registration procedure for disaster roaming services on the selected PLMN as described in subclause 5.5.1 in 3GPP Spec 24.501; and b) if the UE (102) has a stored disaster roaming wait range, the UE (102) shall generate a random number within the disaster roaming wait range and start a timer with the generated random number. While the timer is running, the UE (102) shall not initiate registration on the selected PLMN except if the UE (102) needs to request the emergency PDU session, in which case the UE (102) shall initiate the registration procedure, set the 5GS registration type IE to "emergency registration" in the REGISTRATION REQUEST message and keep the timer running. Upon expiration of the timer, if the UE (102) does not have the emergency PDU session, the UE (102) shall perform a registration procedure for disaster roaming services as described in subclause 5.5.1 if still camped on the selected PLMN. If the UE (102) has the emergency PDU session when the timer expires, the registration procedure for disaster roaming services as described in subclause 5.5.1 shall be performed after the release of the emergency PDU session, if the UE (102) is still camped on the selected PLMN.

[0155] In an embodiment, after the disaster condition has occurred, if the UE (102) receives a REGISTRATION REJECT message while registering for disaster roaming services in a PLMN, the UE (102) shall not use the disaster roaming wait range value again upon selecting a PLMN for disaster roaming services after PLMN selection.

[0156] In an embodiment, after the disaster condition has occurred, if the UE (102) receives a REGISTRATION REJECT message while registering for disaster roaming services in a PLMN, the UE (102) shall not use the disaster roaming wait range value again, upon selecting a PLMN for disaster roaming services after PLMN selection as specified in 3GPP TS 23.122.

[0157] In an embodiment, upon expiry of the timer for disaster roaming wait range, the UE shall not start a timer with the disaster roaming wait range value again until disaster condition has ended.

[0158] In an embodiment, upon selecting a PLMN for disaster roaming as specified in 3GPP TS 23.122, if the UE (102) receives a REGISTRATION REJECT message while registering for disaster roaming services in the PLMN, the UE (102) shall not use the disaster roaming wait range value again, upon selecting a PLMN for disaster roaming services after PLMN selection.

[0159] In an embodiment, upon selecting a PLMN for disaster roaming as specified in 3GPP TS 23.122, if the UE (102) receives a REGISTRATION REJECT message while registering for disaster roaming services in the PLMN, the UE (102) shall not use the disaster roaming wait range value again, upon selecting a PLMN for disaster roaming services after PLMN selection as specified in 3GPP TS 23.122

[0160] In an embodiment, if the UE (102) receives a REGISTRATION REJECT message while registering for disaster roaming services in the PLMN, the UE (102) shall not use the disaster roaming wait range value again, upon selecting a PLMN for disaster roaming services as specified in 3GPP TS 23.122.

[0161] In an embodiment, upon selecting a PLMN for disaster roaming as specified in 3GPP TS 23.122 if the UE (102) has waited for the timer generated from the disaster roaming wait range (e.g., disaster roaming wait range duration) before registering on the selected PLMN (e.g., selected forbidden PLMN, PLMN-A1), if the UE (102) receives a REGISTRATION REJECT message while registering for disaster roaming services in a PLMN, the UE (102) shall not use the disaster roaming wait range value again upon selecting a PLMN for disaster roaming services after PLMN selection.

[0162] In an embodiment, if the UE (102) receives a REGISTRATION REJECT message while registering for disaster roaming services in the PLMN, the UE (102) shall not use the disaster roaming wait range value again, upon selecting a PLMN for disaster roaming as specified in 3GPP TS 23.122, if the UE (102) has waited for the timer generated from disaster roaming wait range (for e.g. disaster roaming wait range duration) before registering on the selected PLMN (for e.g. selected forbidden PLMN, PLMN-A1).

[0163] In an embodiment, upon selecting a PLMN for disaster roaming as specified in 3GPP TS 23.122, if the UE (102) has waited for the timer generated from the disaster roaming wait range (e.g., disaster roaming wait range duration) before registering on the selected PLMN (e.g., selected forbidden PLMN, PLMN-A1), if the UE (102) receives the REGISTRATION REJECT message while registering for disaster roaming services in a PLMN, the UE (102) shall not use the disaster roaming wait range value again upon selecting the same selected PLMN (e.g., selected forbidden PLMN, PLMN-A1) after PLMN selection.

[0164] In an embodiment, if the UE (102) receives a REGISTRATION REJECT message while registering for disaster roaming services in a PLMN (for e.g. PLMN-A1), the UE (102) shall not use the disaster roaming wait range value again, upon selecting same PLMN (for e.g. PLMN-A1) for disaster roaming as specified in 3GPP TS 23.122, if the UE (102) has waited for the timer generated from disaster roaming wait range (for e.g. disaster roaming wait range duration) before registering on the selected PLMN(for e.g. selected forbidden PLMN, PLMN-A1).

[0165] In an embodiment, upon selecting a PLMN for disaster roaming as specified in 3GPP TS 23.122, if the UE (102) has waited for the timer generated from the disaster roaming wait range (e.g., disaster roaming wait range duration) before registering on the selected PLMN (e.g., selected forbidden PLMN, PLMN-A1), if the UE (102) receives a REGISTRATION REJECT message while registering for disaster roaming services in a PLMN, the UE (102) shall not use the disaster roaming wait range value again upon selecting a PLMN (e.g., after PLMN selection) (e.g., forbidden PLMN PLMN-A2) other than or different from the previously selected PLMN (e.g., PLMN-A1) on which the UE (102) received the REGISTRATION REJECT message or the registration was not successful.

[0166] In an embodiment, if the UE (102) receives a REGISTRATION REJECT message while registering for disaster roaming services in a PLMN (for e.g. PLMN-A1), the UE (102) shall not use the disaster roaming wait range value again, upon selecting a PLMN (for e.g. PLMN-A2) for disaster roaming as specified in 3GPP TS 23.122, other than or different from the previously selected PLMN (for e.g. PLMN-A1) on which UE (102) received the REGISTRATION REJECT message or the registration was not successful and on which the UE (102) has waited for the timer generated from disaster roaming wait range (for e.g. disaster roaming wait range duration) before registering on the selected PLMN(for e.g. PLMN-A1).

[0167] In an embodiment, upon selecting a PLMN for disaster roaming as specified in 3GPP TS 23.122, if the UE (102) has waited for the timer generated from the disaster roaming wait range (e.g., disaster roaming wait range duration) before registering on the selected PLMN (e.g., selected forbidden PLMN, PLMN-A1), if the UE (102) receives a REGISTRATION REJECT message while registering for disaster roaming services in a PLMN, the UE (102) shall use the disaster roaming wait range value again and wait for the disaster roaming wait range duration upon selecting a PLMN (e.g., after PLMN selection) (e.g., forbidden PLMN PLMN-A2) other than or different from the previously selected PLMN (e.g., PLMN-A1) on which the UE (102) received the REGISTRATION REJECT message or the registration was not successful.

[0168] In an embodiment, if the UE (102) receives a REGISTRATION REJECT message while registering for disaster roaming services in a PLMN (for e.g. PLMN-A1), the UE (102) shall use the disaster roaming wait range value again and wait for the disaster roaming wait range duration, upon selecting a PLMN (for e.g. PLMN-A2) for disaster roaming as specified in 3GPP TS 23.122 other than or different from the previously selected PLMN (for e.g. PLMN-A1) on which the UE (102) received the REGISTRATION REJECT message or the registration was not successful and on which the UE has waited for the timer generated from disaster roaming wait range (for e.g. disaster roaming wait range duration) before registering on the selected PLMN(for e.g. PLMN-A1).

[0169] The term UE (102) performs PLMN selection refers to PLMN selection procedure as specified in 3GPP TS 23.122

[0170] The procedures and solutions defined in this embodiment for "after the disaster condition has occurred" are also applicable for "Upon selecting a PLMN for disaster roaming as specified in 3GPP TS 23.122".

[0171] The procedures and solutions defined in this embodiment for "Upon selecting a PLMN for disaster roaming as specified in 3GPP TS 23.122" are also applicable for "after the disaster condition has occurred".

[0172] The terms "MS Determined PLMN with disaster condition" and "UE determined PLMN with disaster condition" are used interchangeably and have the same meaning.

[0173] The solutions explained in this embodiment are explained using Registration Reject as an example. However, the solutions are not restricted to Registration Reject procedure and are also applicable for any procedure when the UE selects a PLMN for disaster roaming services or when the UE selects a PLMN for the normal services after disaster condition has ended.

[0174] The UE (102) shall perform the below steps in any order or combinations:

[0175] In an embodiment, upon selecting the PLMN for disaster roaming as specified in 3GPP TS 23.122, if the UE (102) has a stored disaster roaming wait range (for example, in USIM or ME) and it was not registered on the selected PLMN for disaster roaming service and not waited for the time duration of the generated random number within the disaster roaming wait range (for example, during a disaster condition / situation if the UE (102) was not registered on the selected PLMN for disaster roaming service (optionally not even once) and the UE (102) has not waited for the time duration of the generated random number within the disaster roaming wait range), the UE (102) shall generate a random number within the disaster roaming wait range and start a timer with the generated random number. While the timer is running, the UE (102) shall not initiate registration on the selected PLMN except if the UE (102) needs to request the emergency PDU session, in which case the UE (102) shall initiate the registration procedure for emergency services, set the 5GS registration type IE to "emergency registration" in the REGISTRATION REQUEST message or any NAS signaling message, and keep the timer running. Upon expiration of the timer, if the UE (102) does not have the emergency PDU session, the UE (102) shall perform a registration procedure for disaster roaming services if still camped on the selected PLMN. Upon expiration of the timer, if the UE (102) has the emergency PDU session when the timer expires, the UE (102) shall initiate the registration procedure after the release of the emergency PDU session if the UE is still camped on the selected PLMN.

[0176] In an embodiment, upon selecting the PLMN for the disaster roaming as specified in 3GPP TS 23.122, if the UE (102) has the stored disaster roaming wait range optionally for the selected PLMN (or optionally for the selected PLMN and RAT combination) and it was not registered on the selected PLMN (or optionally on the selected PLMN and RAT combination) for disaster roaming service and not waited for the time duration of the generated random number within the disaster roaming wait range optionally for / on the selected PLMN (or optionally for / on the selected PLMN and RAT combination) (for example, during a disaster condition / situation if the UE (102) was not registered on the selected PLMN or selected PLMN+RAT combination for disaster roaming service (optionally not even once) and the UE (102) has not waited for the time duration of the generated random number within the disaster roaming wait range for / on the selected PLMN or selected PLMN+RAT combination), the UE (102) shall generate a random number within the disaster roaming wait range and start a timer with the generated random number. While the timer is running, the UE (102) shall not initiate registration on the selected PLMN except if the UE (102) needs to request an emergency PDU session, in which case the UE (102) shall initiate the registration procedure for emergency services, set the 5GS registration type IE to "emergency registration" in the REGISTRATION REQUEST message or any NAS signaling message, and keep the timer running. Upon expiration of the timer, if the UE (102) does not have an emergency PDU session, the UE (102) shall perform the registration procedure for disaster roaming services if still camped on the selected PLMN. Upon expiration of the timer, if the UE (102) has an emergency PDU session when the timer expires, the UE (102) shall initiate the registration procedure after the release of the emergency PDU session if the UE (102) is still camped on the selected PLMN.

[0177] In an embodiment, upon selecting the PLMN for disaster roaming as specified in 3GPP TS 23.122, if the UE (102) has a stored disaster roaming wait range and it was not registered on the selected PLMN for disaster roaming service (for example, during a disaster condition / situation if the UE was not registered on the selected PLMN for disaster roaming service, optionally not even once), the UE (102) shall generate a random number within the disaster roaming wait range and start a timer with the generated random number. While the timer is running, the UE (102) shall not initiate registration on the selected PLMN except if the UE (102) needs to request an emergency PDU session, in which case the UE (102) shall initiate the registration procedure for emergency services, set the 5GS registration type IE to "emergency registration" in the REGISTRATION REQUEST message or any NAS signaling message, and keep the timer running. Upon expiration of the timer, if the UE (102) does not have an emergency PDU session, the UE (102) shall perform a registration procedure for disaster roaming services if still camped on the selected PLMN. Upon expiration of the timer, if the UE (102) has the emergency PDU session when the timer expires, the UE (102) shall initiate the registration procedure after the release of the emergency PDU session if the UE (102) is still camped on the selected PLMN.

[0178] In an embodiment, upon selecting a PLMN for disaster roaming as specified in 3GPP TS 23.122, if the UE (102) has a stored disaster roaming wait range and it was not registered on the selected PLMN for disaster roaming service, optionally for the MS determined PLMN with disaster condition (for example, PLMN-D) (for example, during a disaster condition / situation if the UE (102) was not registered on the selected PLMN for disaster roaming service, optionally not even once, for the MS determined PLMN with disaster condition (for example, PLMN-D)), the UE (102) shall generate a random number within the disaster roaming wait range and start a timer with the generated random number. While the timer is running, the UE (102) shall not initiate registration on the selected PLMN except if the UE needs to request an emergency PDU session, in which case the UE (102) shall initiate the registration procedure for emergency services, set the 5GS registration type IE to "emergency registration" in the REGISTRATION REQUEST message or any NAS signaling message, and keep the timer running. Upon expiration of the timer, if the UE (102) does not have an emergency PDU session, the UE (102) shall perform a registration procedure for disaster roaming services if still camped on the selected PLMN. Upon expiration of the timer, if the UE (102) has an emergency PDU session when the timer expires, the UE shall initiate the registration procedure after the release of the emergency PDU session if the UE (102) is still camped on the selected PLMN.

[0179] In an embodiment, upon selecting a PLMN for disaster roaming as specified in 3GPP TS 23.122, if the UE (102) has a stored disaster roaming wait range, optionally for the selected PLMN (or optionally for the selected PLMN and RAT combination), and it was not registered on the selected PLMN (or optionally on the selected PLMN and RAT combination) for disaster roaming service, optionally for the MS determined PLMN with disaster condition (for example, PLMN-D), and not waited for the time duration of the generated random number within the disaster roaming wait range, optionally for / on the selected PLMN (or optionally for / on the selected PLMN and RAT combination), optionally for the MS determined PLMN with disaster condition (for example, PLMN-D) (for example, during a disaster condition / situation if the UE (102) was not registered on the selected PLMN or selected PLMN+RAT combination for disaster roaming service, optionally not even once, for the MS determined PLMN with disaster condition (for example, PLMN-D), and the UE (102) has not waited for the time duration of the generated random number within the disaster roaming wait range for / on the selected PLMN or selected PLMN+RAT combination (for example, PLMN-A1) for the MS determined PLMN with disaster condition (for example, PLMN-D)), the UE (102) shall generate a random number within the disaster roaming wait range and start a timer with the generated random number. While the timer is running, the UE (102) shall not initiate registration on the selected PLMN except if the UE (102) needs to request an emergency PDU session, in which case the UE (102) shall initiate the registration procedure for emergency services, set the 5GS registration type IE to "emergency registration" in the REGISTRATION REQUEST message or any NAS signaling message, and keep the timer running. Upon expiration of the timer, if the UE (102) does not have an emergency PDU session, the UE (102) shall perform a registration procedure for disaster roaming services if still camped on the selected PLMN. Upon expiration of the timer, if the UE (102) has an emergency PDU session when the timer expires, the UE (102) shall initiate the registration procedure after the release of the emergency PDU session if the UE (102) is still camped on the selected PLMN.

[0180] In an embodiment, upon selecting a PLMN for disaster roaming as specified in 3GPP TS 23.122, if the UE (102) has a stored disaster roaming wait range and the UE (102) was previously registered for the normal services (for example, UE (102) was not registered for disaster roaming services on any PLMN or PLMN and RAT combination, optionally for the MS determined PLMN with disaster condition (for example, PLMN-D)) (for example, UE (102) is / was not registered for disaster roaming services even once during disaster condition / situation, optionally for the MS determined PLMN with disaster condition (for example, PLMN-D)), the UE (102) shall generate a random number within the disaster roaming wait range and start a timer with the generated random number. While the timer is running, the UE (102) shall not initiate registration on the selected PLMN except if the UE (102) needs to request an emergency PDU session, in which case the UE (102) shall initiate the registration procedure for emergency services, set the 5GS registration type IE to "emergency registration" in the REGISTRATION REQUEST message or any NAS signaling message, and keep the timer running. Upon expiration of the timer, if the UE (102) does not have an emergency PDU session, the UE (102) shall perform a registration procedure for disaster roaming services if still camped on the selected PLMN. Upon expiration of the timer, if the UE (102) has an emergency PDU session when the timer expires, the UE (102) shall initiate the registration procedure after the release of the emergency PDU session if the UE (102) is still camped on the selected PLMN.

[0181] In an embodiment, upon selecting a PLMN for disaster roaming as specified in 3GPP TS 23.122, if the UE (102) has a stored disaster roaming wait range and the UE (102) was previously not registered for disaster roaming services, optionally on any PLMN or optionally on any PLMN and RAT combination (for example, UE (102) was not registered for disaster roaming services on any PLMN or PLMN and RAT combination, optionally for the MS determined PLMN with disaster condition (for example, PLMN-D)) (for example, the UE (102) is / was not registered for disaster roaming services even once during disaster condition / situation, optionally for the MS determined PLMN with disaster condition (for example, PLMN-D)), the UE (102) shall generate a random number within the disaster roaming wait range and start a timer with the generated random number. While the timer is running, the UE (102) shall not initiate registration on the selected PLMN except if the UE (102) needs to request an emergency PDU session, in which case the UE (102) shall initiate the registration procedure for emergency services, set the 5GS registration type IE to "emergency registration" in the REGISTRATION REQUEST message or any NAS signaling message, and keep the timer running. Upon expiration of the timer, if the UE (102) does not have an emergency PDU session, the UE (102) shall perform a registration procedure for disaster roaming services if still camped on the selected PLMN. Upon expiration of the timer, if the UE (102) has an emergency PDU session when the timer expires, the UE (102) shall initiate the registration procedure after the release of the emergency PDU session if the UE (102) is still camped on the selected PLMN.

[0182] In an embodiment, upon selecting a PLMN for disaster roaming as specified in 3GPP TS 23.122, if the UE (102) has a stored disaster roaming wait range and the UE (102) was previously not registered for disaster roaming services, optionally on any PLMN (or optionally on any PLMN and RAT combination), optionally for the MS determined PLMN with disaster condition (for example, the UE (102) was not registered for disaster roaming services on any PLMN or PLMN and RAT combination, optionally for the MS determined PLMN with disaster condition (for example, PLMN-D)) (for example, the UE (102) is / was not registered for disaster roaming services even once during disaster condition / situation, optionally for the MS determined PLMN with disaster condition (for example, PLMN-D)), the UE (102) shall generate a random number within the disaster roaming wait range and start a timer with the generated random number. While the timer is running, the UE (102) shall not initiate registration on the selected PLMN except if the UE (102) needs to request the emergency PDU session, in which case the UE (102) shall initiate the registration procedure for emergency services, set the 5GS registration type IE to "emergency registration" in the REGISTRATION REQUEST message or any NAS signaling message, and keep the timer running. Upon expiration of the timer, if the UE (102) does not have an emergency PDU session, the UE (102) shall perform a registration procedure for disaster roaming services if still camped on the selected PLMN. Upon expiration of the timer, if the UE (102) has an emergency PDU session when the timer expires, the UE (102) shall initiate the registration procedure after the release of the emergency PDU session if the UE (102) is still camped on the selected PLMN.

[0183] In an embodiment, upon selecting a PLMN for disaster roaming as specified in 3GPP TS 23.122, if the UE has a stored disaster roaming wait range and the UE (102) was previously registered for disaster roaming services, optionally on any PLMN (or optionally any PLMN and RAT combination) different / other than the selected PLMN (optionally different / other than the selected PLMN and RAT combination), optionally for the MS determined PLMN with disaster condition (for example, the UE (102) was not registered for disaster roaming services on the selected PLMN or PLMN and RAT combination (for example, PLMN-A1) and may be previously registered for disaster roaming services on any other PLMN (or PLMN and RAT combination) (for example, PLMN-A2) other than the selected PLMN, optionally for the MS determined PLMN with disaster condition (for example, PLMN-D)) (for example, the UE (102) was previously registered for disaster roaming services on PLMN-A2 and has now selected PLMN-A1 for disaster roaming services during a disaster condition / situation, optionally for the MS determined PLMN with disaster condition (for example, PLMN-D)), the UE (102) shall generate a random number within the disaster roaming wait range and start a timer with the generated random number. While the timer is running, the UE (102) shall not initiate registration on the selected PLMN except if the UE (102) needs to request an emergency PDU session, in which case the UE (102) shall initiate the registration procedure for emergency services, set the 5GS registration type IE to "emergency registration" in the REGISTRATION REQUEST message or any NAS signaling message, and keep the timer running. Upon expiration of the timer, if the UE (102) does not have an emergency PDU session, the UE (102) shall perform a registration procedure for disaster roaming services if still camped on the selected PLMN. Upon expiration of the timer, if the UE (102) has an emergency PDU session when the timer expires, the UE (102) shall initiate the registration procedure after the release of the emergency PDU session if the UE (102) is still camped on the selected PLMN.

[0184] In an embodiment, upon selecting the PLMN for disaster roaming as specified in 3GPP TS 23.122, if the UE (102) has a stored disaster roaming wait range and the UE (102) has not started / run the timer / time duration (for ex- the Disaster roaming wait timer) of the generated random number within the disaster roaming wait range for / on the selected PLMN (or optionally selected PLMN and RAT combination) at least once, optionally for the MS determined PLMN with disaster condition, optionally after the disaster condition / situation has occurred (for ex- during disaster condition / situation if the UE (102) has not started / run the time duration of the generated random number within the disaster roaming wait range for / on the selected PLMN or selected PLMN+RAT combination (for example PLMN-A1) even once, optionally for the MS determined PLMN with disaster condition (for example PLMN-D)), the UE (102) shall generate a random number within the disaster roaming wait range and start a timer with the generated random number. While the timer is running, the UE (102) shall not initiate registration on the selected PLMN except if the UE (102) needs to request an emergency PDU session, in which case the UE (102) shall initiate the registration procedure for emergency services, set the 5GS registration type IE to "emergency registration" in the REGISTRATION REQUEST message or any NAS signalling message, and keep the timer running. Upon expiration of the timer, if the UE (102) does not have the emergency PDU session, the UE (102) shall perform a registration procedure for disaster roaming services if still camped on the selected PLMN. Upon expiration of the timer, if the UE (102) has an emergency PDU session when the timer expires, the UE (102) shall initiate the registration procedure after the release of the emergency PDU session if the UE (102) is still camped on the selected PLMN.

[0185] In an embodiment, upon selecting the PLMN for disaster roaming as specified in 3GPP TS 23.122, if the UE (102) has a stored disaster roaming wait range and the UE (102) has not started / run the timer / time duration (for ex- the Disaster roaming wait timer) of the generated random number within the disaster roaming wait range for / on any PLMN (or optionally for / on any PLMN and RAT combination) at least once, optionally for the MS determined PLMN with disaster condition, optionally after the disaster condition / situation has occurred (for ex- during disaster condition / situation if the UE (102) has not started / run the time duration of the generated random number within the disaster roaming wait range for / on any PLMN (or PLMN and RAT combination) even once, optionally for the MS determined PLMN with disaster condition (for example PLMN-D)), the UE shall generate a random number within the disaster roaming wait range and start a timer with the generated random number. While the timer is running, the UE (102) shall not initiate registration on the selected PLMN except if the UE (102) needs to request an emergency PDU session, in which case the UE (102) shall initiate the registration procedure for emergency services, set the 5GS registration type IE to "emergency registration" in the REGISTRATION REQUEST message or any NAS signaling message, and keep the timer running. Upon expiration of the timer, if the UE (102) does not have an emergency PDU session, the UE (102) shall perform a registration procedure for disaster roaming services if still camped on the selected PLMN. Upon expiration of the timer, if the UE (102) has the emergency PDU session when the timer expires, the UE (102) shall initiate the registration procedure after the release of the emergency PDU session if the UE (102) is still camped on the selected PLMN.

[0186] In an embodiment, upon selecting a PLMN for disaster roaming as specified in 3GPP TS 23.122, if the UE (102) has a stored disaster roaming wait range and the UE (102) has not waited for the timer / time duration (for ex- the Disaster roaming wait timer) (for example UE (102) has not waited for the timer to expire or the UE (102) has not executed the full wait timer / time duration) of the generated random number within the disaster roaming wait range to expire for / on the selected PLMN (or optionally selected PLMN and RAT combination) not even once, optionally for the MS determined PLMN with disaster condition, optionally after the disaster condition / situation has occurred (for ex- during disaster condition / situation if the UE (102) has not waited for the time duration of the generated random number within the disaster roaming wait range to expire for / on the selected PLMN or selected PLMN+RAT combination (for example PLMN-A1) at least once, optionally for the MS determined PLMN with disaster condition (for example PLMN-D)), the UE (102) shall generate a random number within the disaster roaming wait range and start a timer with the generated random number. While the timer is running, the UE (102) shall not initiate registration on the selected PLMN except if the UE (102) needs to request an emergency PDU session, in which case the UE (102) shall initiate the registration procedure for emergency services, set the 5GS registration type IE to "emergency registration" in the REGISTRATION REQUEST message or any NAS signalling message, and keep the timer running. Upon expiration of the timer, if the UE (102) does not have an emergency PDU session, the UE (102) shall perform a registration procedure for disaster roaming services if still camped on the selected PLMN. Upon expiration of the timer, if the UE (102) has an emergency PDU session when the timer expires, the UE (102) shall initiate the registration procedure after the release of the emergency PDU session if the UE (102) is still camped on the selected PLMN.

[0187] In an embodiment, upon selecting the PLMN for disaster roaming as specified in 3GPP TS 23.122, if the UE has a stored disaster roaming wait range and the UE (102) has not waited for the timer / time duration (for example, the Disaster roaming wait timer) (for example, the UE (102) has not waited for the timer to expire or the UE (102) has not executed the full wait timer / time duration) of the generated random number within the disaster roaming wait range to expire for / on any PLMN (or optionally for / on any PLMN and RAT combination) not even once, optionally for the MS determined PLMN with disaster condition, optionally after the disaster condition / situation has occurred (for example, during the disaster condition / situation if the UE (102) has not waited for the time duration of the generated random number within the disaster roaming wait range to expire for / on any PLMN (or PLMN and RAT combination) at least once, optionally for the MS determined PLMN with disaster condition (for example, PLMN-D)), the UE (102) shall generate a random number within the disaster roaming wait range and start the timer with the generated random number. While the timer is running, the UE (102) shall not initiate registration on the selected PLMN except if the UE (102) needs to request an emergency PDU session, in which case the UE (102) shall initiate the registration procedure for emergency services, set the 5GS registration type IE to "emergency registration" in the REGISTRATION REQUEST message or any NAS signaling message, and keep the timer running. Upon expiration of the timer, if the UE (102) does not have an emergency PDU session, the UE shall perform a registration procedure for disaster roaming services if still camped on the selected PLMN. Upon expiration of the timer, if the UE (102) has the emergency PDU session when the timer expires, the UE (102) shall initiate the registration procedure after the release of the emergency PDU session if the UE is still camped on the selected PLMN.

[0188] In an embodiment, upon selecting a PLMN for disaster roaming as specified in 3GPP TS 23.122, if the UE (102) has a stored disaster roaming wait range and the UE (102) is not running any other timers for the selected PLMN (optionally selected PLMN + RAT combination) due to any of the 5GMM or 5GS Session Management (5GSM) reject causes as mentioned in 3GPP TS 24.501, the UE (102) shall generate a random number within the disaster roaming wait range and start a timer with the generated random number. While the timer is running, the UE (102) shall not initiate registration on the selected PLMN except if the UE (102) needs to request an emergency PDU session, in which case the UE (102) shall initiate the registration procedure for emergency services, set the 5GS registration type IE to "emergency registration" in the REGISTRATION REQUEST message or any NAS signaling message and keep the timer running. Upon expiration of the timer, if the UE (102) does not have an emergency PDU session, the UE (102) shall perform a registration procedure for disaster roaming services if still camped on the selected PLMN. Upon expiration of the timer, if the UE (102) has an emergency PDU session when the timer expires, the UE (102) shall initiate registration procedure after the release of the emergency PDU session, if the UE (102) is still camped on the selected PLMN.

[0189] In an embodiment, if the UE (102) was previously registered for disaster roaming services on the selected PLMN / PLMN+RAT combination or any of the PLMN / PLMN+RAT combinations, or if the UE (102) needs to start / run the disaster roaming wait range / timer for the selected PLMN (optionally selected PLMN + RAT combination) or any of the PLMN(s) (optionally selected PLMN + RAT combination) providing disaster roaming services any time after the disaster condition has occurred, the UE (102) may optionally start a disaster roaming wait range / timer with a random value generated between 0 and the difference (i.e., remaining time) of the value between the previously run timer and the current value of the disaster roaming wait range / timer. if the previously run timer value is more than the current disaster roaming wait range / timer or if the difference (i.e., remaining time) between the previously run timer and the current disaster roaming wait range is less than 0, the UE (102) may optionally not start any timer or may start a wait timer with a random value between 0 and not exceeding the disaster roaming wait range. For example, if the UE (102) performs PLMN selection and selects another forbidden PLMN for disaster roaming services when the timer for the disaster roaming wait range is running or has already run once, the UE (102) shall behave as:

[0190] Let t1 be the time remaining for the timer for disaster roaming wait range timeout when the UE (102) performed PLMN selection for disaster roaming services, and let t be the time elapsed between when the UE (102) performed PLMN selection and selected another forbidden PLMN for disaster roaming services. if t1 is greater than t, then the timer shall be restarted with the value t1 - t. if t1 is equal to or less than t, then the timer need not be restarted. if the UE is not capable of determining t, then the UE (102) shall restart the timer with the value t1.

[0191] In an embodiment, upon selecting a PLMN for disaster roaming as specified in 3GPP TS 23.122, If the UE has a stored disaster roaming wait range and it was registered on the selected PLMN for disaster roaming service and / or the UE (102) has waited for the time duration of the generated random number within the disaster roaming wait range (for example, during a disaster condition / situation if the UE (102) was registered on the selected PLMN for disaster roaming service (optionally at least once) or the UE (102) has waited for the time duration of the generated random number within the disaster roaming wait range), the UE (102) shall NOT generate a random number within the disaster roaming wait range and shall NOT start a timer with the generated random number. The UE (102) shall perform registration or any NAS / AS signaling procedure on the selected PLMN.

[0192] In an embodiment, upon selecting the PLMN for disaster roaming as specified in 3GPP TS 23.122, If the UE (102) has a stored disaster roaming wait range optionally for the selected PLMN (or optionally for the selected PLMN and RAT combination) and it was registered on the selected PLMN (or optionally on the selected PLMN and RAT combination) for disaster roaming service and / or the UE (102) has waited for the time duration of the generated random number within the disaster roaming wait range optionally for / on the selected PLMN (or optionally for / on the selected PLMN and RAT combination) (for example, during a disaster condition / situation if the UE (102) was registered on the selected PLMN or selected PLMN+RAT combination for disaster roaming service (optionally at least once) and / or the UE (102) has waited for the time duration of the generated random number within the disaster roaming wait range for / on the selected PLMN or selected PLMN+RAT combination), the UE (102) shall NOT generate a random number within the disaster roaming wait range and shall NOT start a timer with the generated random number. The UE (102) shall perform registration or any NAS / AS signaling procedure on the selected PLMN.

[0193] In an embodiment, upon selecting a PLMN for disaster roaming as specified in 3GPP TS 23.122, If the UE (102) has a stored disaster roaming wait range and it was registered on the selected PLMN for disaster roaming service (for example, during a disaster condition / situation if the UE (102) was registered on the selected PLMN for disaster roaming service (optionally at least once)), the UE (102) shall NOT generate a random number within the disaster roaming wait range and shall NOT start a timer with the generated random number. The UE (102) shall perform registration on the selected PLMN.

[0194] In an embodiment, upon selecting a PLMN for disaster roaming as specified in 3GPP TS 23.122, If the UE (102) has a stored disaster roaming wait range and it was registered on the selected PLMN for disaster roaming service, optionally for the MS determined PLMN with disaster condition (for example, PLMN-D) (for example, during disaster condition / situation if the UE was registered on the selected PLMN for disaster roaming service (optionally at least once) for the MS determined PLMN with disaster condition (for example, PLMN-D)), the UE (102) shall NOT generate a random number within the disaster roaming wait range and shall NOT start a timer with the generated random number. The UE (102) shall perform registration or any NAS / AS signaling procedure on the selected PLMN.

[0195] In an embodiment, upon selecting the PLMN for disaster roaming as specified in 3GPP TS 23.122, If the UE (102) has the stored disaster roaming wait range optionally for the selected PLMN (or optionally for the selected PLMN and RAT combination) and it was registered on the selected PLMN (or optionally on the selected PLMN and RAT combination) for disaster roaming service optionally for the MS determined PLMN with disaster condition (for example, PLMN-D) and / or the UE (102) has waited for the time duration of the generated random number within the disaster roaming wait range optionally for / on the selected PLMN (or optionally for / on the selected PLMN and RAT combination) optionally for the MS determined PLMN with disaster condition (for example, PLMN-D) (for example, during disaster condition / situation if the UE (102) was registered on the selected PLMN or selected PLMN+RAT combination for disaster roaming service (optionally at least once) for the MS determined PLMN with disaster condition (for example, PLMN-D) and / or the UE (102) has waited for the time duration of the generated random number within the disaster roaming wait range for / on the selected PLMN or selected PLMN+RAT combination (for example, PLMN-A1) for the MS determined PLMN with disaster condition (for example, PLMN-D)), the UE (102) shall NOT generate a random number within the disaster roaming wait range and shall NOT start a timer with the generated random number. The UE (102) shall perform registration or any NAS / AS signalling procedure on the selected PLMN.

[0196] In an embodiment, upon selecting the PLMN for disaster roaming as specified in 3GPP TS 23.122, if the UE (102) has a stored disaster roaming wait range and the UE (102) was previously NOT registered for the normal services (for example, the UE (102) was registered for disaster roaming services on any PLMN or PLMN and RAT combination optionally for the MS determined PLMN with disaster condition (for example, PLMN-D)) (for example, the UE (102) is / was registered for disaster roaming services at least once during disaster condition / situation optionally for the MS determined PLMN with disaster condition (for example, PLMN-D)), the UE (102) shall NOT generate a random number within the disaster roaming wait range and shall NOT start a timer with the generated random number. The UE (102) shall perform registration or any NAS / AS signalling procedure on the selected PLMN.

[0197] In an embodiment, upon selecting the PLMN for disaster roaming as specified in 3GPP TS 23.122, if the UE (102) has the stored disaster roaming wait range and the UE (102) was previously registered for disaster roaming services, optionally on any PLMN or optionally on any PLMN and RAT combination (for example, the UE (102) was registered for disaster roaming services on any PLMN or PLMN and RAT combination optionally for the MS determined PLMN with disaster condition (for example, PLMN-D)) (for example, the UE (102) is / was registered for disaster roaming services at least once during disaster condition / situation optionally for the MS determined PLMN with disaster condition (for example, PLMN-D)), the UE (102) shall NOT generate a random number within the disaster roaming wait range and shall NOT start a timer with the generated random number. The UE (102) shall perform registration or any NAS / AS signaling procedure on the selected PLMN.

[0198] In an embodiment, upon selecting a PLMN for disaster roaming as specified in 3GPP TS 23.122, if the UE (102) has a stored disaster roaming wait range and the UE was previously registered for disaster roaming services, optionally on any PLMN (or optionally on any PLMN and RAT combination), optionally for the MS determined PLMN with disaster condition (for example, the UE (102) was registered for disaster roaming services on any PLMN or PLMN and RAT combination, optionally for the MS determined PLMN with disaster condition (for example, PLMN-D)) (for example, the UE (102) is / was registered for disaster roaming services even once during disaster condition / situation, optionally for the MS determined PLMN with disaster condition (for example, PLMN-D)), the UE (102) shall NOT generate a random number within the disaster roaming wait range and shall NOT start a timer with the generated random number. The UE (102) shall perform registration or any NAS / AS signalling procedure on the selected PLMN.

[0199] In an embodiment, upon selecting a PLMN for disaster roaming as specified in 3GPP TS 23.122, if the UE (102) has a stored disaster roaming wait range and the UE (102) has started / run the timer / time duration (for example, the Disaster roaming wait timer) of the generated random number within the disaster roaming wait range for / on the selected PLMN (or optionally selected PLMN and RAT combination) at least once, optionally for the MS determined PLMN with disaster condition, optionally after the disaster condition / situation has occurred (for example, during disaster condition / situation if the UE (102) has started / run the time duration of the generated random number within the disaster roaming wait range for / on the selected PLMN or selected PLMN+RAT combination (for example, PLMN-A1) at least once, optionally for the MS determined PLMN with disaster condition (for example, PLMN-D)), the UE (102) shall NOT generate a random number within the disaster roaming wait range and shall NOT start a timer with the generated random number. The UE (102) shall perform registration or any NAS / AS signalling procedure on the selected PLMN.

[0200] In an embodiment, upon selecting a PLMN for disaster roaming as specified in 3GPP TS 23.122, if the UE (102) has a stored disaster roaming wait range and the UE (102) has started / run the timer / time duration (for example, the Disaster roaming wait timer) of the generated random number within the disaster roaming wait range for / on any PLMN (or optionally for / on any PLMN and RAT combination) at least once, optionally for the MS determined PLMN with disaster condition, optionally after the disaster condition / situation has occurred (for example, during the disaster condition / situation if the UE (102) has started / run the time duration of the generated random number within the disaster roaming wait range for / on any PLMN (or PLMN and RAT combination) at least once, optionally for the MS determined PLMN with disaster condition (for example, PLMN-D)), the UE (102) shall NOT generate a random number within the disaster roaming wait range and shall NOT start a timer with the generated random number. The UE (102) shall perform registration or any NAS / AS signalling procedure on the selected PLMN.

[0201] In an embodiment, upon selecting a PLMN for disaster roaming as specified in 3GPP TS 23.122, if the UE (102) has a stored disaster roaming wait range and the UE (102) has waited for the timer / time duration (for example, the Disaster roaming wait timer) (for example, the UE has waited for the timer to expire or the UE (102) has executed the full wait timer / time duration) of the generated random number within the disaster roaming wait range to expire for / on the selected PLMN (or optionally selected PLMN and RAT combination) at least once, optionally for the MS determined PLMN with disaster condition, optionally after the disaster condition / situation has occurred (for example, during the disaster condition / situation if the UE (102) has waited for the time duration of the generated random number within the disaster roaming wait range to expire for / on the selected PLMN or selected PLMN+RAT combination (for example, PLMN-A1) at least once, optionally for the MS determined PLMN with disaster condition (for example, PLMN-D)), the UE (102) shall NOT generate a random number within the disaster roaming wait range and shall NOT start a timer with the generated random number. The UE (102) shall perform registration or any NAS / AS signalling procedure on the selected PLMN.

[0202] In an embodiment, upon selecting the PLMN for disaster roaming as specified in 3GPP TS 23.122, if the UE (102) has the stored disaster roaming wait range and the UE (102) has waited for the timer / time duration (for example, the Disaster roaming wait timer) (for example, the UE (102) has waited for the timer to expire or the UE (102) has executed the full wait timer / time duration) of the generated random number within the disaster roaming wait range to expire for / on any PLMN (or optionally for / on any PLMN and RAT combination) at least once, optionally for the MS determined PLMN with disaster condition, optionally after the disaster condition / situation has occurred (for example, during the disaster condition / situation if the UE (102) has waited for the time duration of the generated random number within the disaster roaming wait range to expire for / on any PLMN (or PLMN and RAT combination) at least once, optionally for the MS determined PLMN with disaster condition (for example, PLMN-D)), the UE (102) shall NOT generate a random number within the disaster roaming wait range and shall NOT start a timer with the generated random number. The UE (102) shall perform registration or any NAS / AS signalling procedure on the selected PLMN.

[0203] In an embodiment, upon selecting the PLMN for disaster roaming as specified in 3GPP TS 23.122, if the UE (102) has a stored disaster roaming wait range and the UE (102) is running any other timers for the selected PLMN (optionally selected PLMN + RAT combination) due to any of the 5GMM or 5GSM reject causes as mentioned in 3GPP TS 24.501, the UE (102) shall NOT generate a random number within the disaster roaming wait range and shall NOT start a timer with the generated random number. The UE (102) shall perform registration or any NAS / AS signalling procedure on the selected PLMN.

[0204] FIG. 2A is a sequence diagram that illustrates the existing method where the UE (102) starts a timer for disaster return wait range again and waits for disaster return wait range duration or waits for timer to expire again, even if the timer has already expired once or when UE (102) has already waited once for the disaster return wait range duration, optionally after the disaster condition has ended, according to prior art.

[0205] Upon determining that a disaster condition has ended as specified in 3GPP TS 23.122: a) the UE (102) shall stop the timer started with a generated random number within the disaster roaming wait range, if running; b) the UE (102) shall perform PLMN selection as specified in 3GPP TS 23.122 [5], except if the UE (102) already selected an allowable PLMN as specified in 3GPP TS 23.122 [6]; and c) if the UE (102) selects the determined PLMN with disaster condition and has a stored disaster return wait range, which is 1) provided by the PLMN providing disaster roaming services; or 2) provided by the selected PLMN, the UE (102) shall generate a random number within the disaster return wait range, start a timer with the generated random number value and enter 5GMM-DEREGISTERED.ATTEMPTING-REGISTRATION state or 5GMM-REGISTERED.ATTEMPTING-REGISTRATION-UPDATE state, if registered.

[0206] While the timer is running, the UE (102) shall not initiate registration on the selected PLMN except if the UE (102) needs to request an emergency PDU session, in which case the UE (102) shall initiate the registration procedure, set the 5GS registration type IE to "emergency registration" in the REGISTRATION REQUEST message, and keep the timer running. Upon expiration of the timer, if the UE (102) does not have an emergency PDU session, the UE shall perform a registration procedure if still camped on the selected PLMN. If the UE (102) has an emergency PDU session when the timer expires, the registration procedure as described in subclause 5.5.1 shall be performed after the release of the emergency PDU session if the UE (102) is still camped on the selected PLMN. Otherwise, the UE shall perform registration procedure in the selected PLMN.

[0207] The UE (102) was registered / camped to PLMN-A1 for disaster roaming services. The UE (102) was configured with Disaster Roaming Return Range optionally by the PLMN-D1 or the registered PLMN or the Home PLMN (HPLMN) of the UE (102). Disaster condition ends and the UE (102) determines the disaster condition has ended.

[0208] Upon determining that a disaster condition has ended and selecting an allowable PLMN (for ex- PLMN-D1) optionally previously with disaster condition (for ex- PLMN-D1) or the UE (102) determined PLMN with disaster condition, if there is a disaster return wait range stored in the ME optionally provided by the PLMN providing disaster roaming services or provided by the selected PLMN, the UE (102) shall generate a random number within the disaster return wait range and start a timer set to the generated random number. While the timer is running, the UE (102) shall not initiate registration on the selected PLMN except if the UE (102) needs to request an emergency PDU session, in which case the UE (102) shall initiate the registration procedure, set the 5GS registration type IE to "emergency registration" in the REGISTRATION REQUEST message, and keep the timer running. Upon expiration of the timer, if the UE (102) does not have an emergency PDU session, the UE shall perform a registration procedure if still camped on the selected PLMN. If the UE has an emergency PDU session when the timer expires, the registration procedure as described in subclause 5.5.1 shall be performed after the release of the emergency PDU session, if the UE (102) is still camped on the selected PLMN.

[0209] However, there may be situations where, after the UE (102) has waited for the timer generated from the disaster return wait range (for example, disaster return wait range duration) or after the expiry of the timer for disaster return wait range, before registering on the UE determined PLMN with disaster condition or the selected allowable PLMN (PLMN-D1), the UE (102) may have to perform PLMN selection again to select another allowable PLMN (for example, PLMN-D2) for the normal services. Some examples of the situations (but not restricted to these examples) are: 1) when the UE (102) gets a registration reject or any reject cause on the first selected allowable PLMN (i.e., PLMN-D1) or the UE (102) determined PLMN with disaster condition and selects another allowable PLMN (i.e., PLMN-D2); or 2) when the UE (102) faces Out-of-service (OOS) or Radio-Link-Failure (RLF) or No-Service or lack of coverage on the selected PLMN and selects another PLMN; or 3) when the UE (102) loses the services of the first selected allowable PLMN (for example, PLMN-D1) or the UE (102) determined PLMN with disaster condition and selects / camps on another selected allowable PLMN (for example, PLMN-D2), etc.

[0210] Similarly, there may be situations, for example: 1) when the UE (102) may select / move from the first selected allowable PLMN (i.e., PLMN-D1) or the UE determined PLMN with disaster condition to another selected allowable PLMN (for example, PLMN-D2) for normal service and may select the first selected allowable PLMN (i.e., PLMN-D1) again (for example, PLMN-D1 to PLMN-D2 to PLMN-D1); or 2) when the UE may select the first selected allowable PLMN (for example, PLMN-D1), start a timer with a generated random number within the disaster return wait range, and on expiry of the timer, the UE (102) is not able to find coverage of the selected PLMN. After some time, the UE (102) selects the same PLMN (for example, PLMN-D1) again.

[0211] In an embodiment, there may be a situation where once the UE (102) has waited for disaster return wait range duration optionally before registering on the UE (102) determined PLMN with disaster condition or the selected allowable PLMN (for example, PLMN-D1) or after the expiry of the timer for disaster return wait range, the UE attempts registration on the selected PLMN or UE (102) determined PLMN with disaster condition for normal services and the registration is rejected or the registration is not successful due to any reasons. The UE (102) may perform PLMN Selection again to select another PLMN (for e.g. PLMN-D2) for normal services.

[0212] In these situations, if there is a disaster return wait range stored in the ME / UE (102) optionally for the selected PLMN (for example, PLMN-D1 or PLMN-D2) optionally provided by the PLMN providing disaster roaming services or provided by the selected PLMN, the UE (102) shall generate a random number within the disaster return wait range and start a timer (for example, disaster return wait timer) set to the generated random number. While the timer is running, the MS shall not initiate registration with the exception of performing an initial registration for emergency services in the selected PLMN (i.e., PLMN-D1 or PLMN-D2). The UE (102) shall start the timer every time and the UE (102) selects the PLMN until the UE (102) is registered for the normal services. For example, UE (102) shall start a timer (for example, disaster return wait timer) for the first selected PLMN (for example, PLMN-D1). If the UE (102) selects another PLMN (for example, PLMN-D2) or if the UE (102) selects the same PLMN (for example, PLMN-D1) again, the UE (102) shall again start a timer (for example, disaster return wait timer) for the selected PLMN (for example, PLMN-D1 or PLMN-D2).

[0213] However, the UE (102) has already started or run the disaster return wait range timer once for the UE (102) determined PLMN with disaster condition or the previously selected allowable PLMN for normal services (for example, PLMN-D1) or the timer for disaster return wait range has already expired once. If the UE (102) shall start / run the disaster return wait range timer for current selected PLMN (for e.g. PLMN-D2) or any other selected PLMN(s) providing normal services to the UE optionally before triggering registration on the selected PLMN, it may lead to a delay in the normal services for the UE (102). Currently, there is no way for the UE (102) to handle this situation and a method needs to be defined.

[0214] As illustrated in FIG 2A, at step 1, disaster condition occurs on the second PLMN (104b) (for example, UE (102) determined PLMN with disaster condition is the second PLMN (104b)). At step 2, the UE (102) is registered to the first PLMN (104a) for disaster roaming services. At step 3, disaster condition ends on the second PLMN (104b). At step 4, upon determining that a disaster condition has ended as specified in 3GPP TS 23.122, the UE (102) performs the PLMN selection and selects UE (102) determined PLMN with disaster condition (for example, the second PLMN (104b)) or any allowable PLMN for normal services. The UE (102) starts a timer generated from disaster return wait range optionally provided by the PLMN providing disaster roaming services (for example, the first PLMN (104a)) or provided by the selected PLMN (for example, the second PLMN (104b)). The UE (102) waits for disaster return wait range duration. At step 5, after the UE (102) has waited for disaster return wait range duration or upon expiry of the timer for disaster return wait range, the UE (102) registers on the second PLMN (104b) for normal services. At step 6, the UE (102) receives a registration reject from the second PLMN (104b) or the registration is not successful on the second PLMN (104b) due to any reasons. At step 7, the UE performs PLMN selection as specified in 3GPP TS 23.122 and selects same or another allowable PLMN (for example, third PLMN (104c)) for normal services. In an embodiment, the UE (102) may select the second PLMN (104b) again for normal services. At step 8, the UE (102) again runs / starts a timer value set to a random number within the disaster return wait range and UE (102) waits for the timer (for example, disaster return wait range duration) to expire to perform registration on the selected PLMN (for example, third PLMN (104c)). At step 9, after the UE (102) has waited for disaster return wait range duration, the UE (102) registers on the third PLMN (104c) for normal services. At step 8, the UE (102) again runs and waits for disaster return wait range duration even when the UE (102) has already waited once for the disaster return wait range duration optionally after the disaster condition has ended. This leads to a delay in getting normal services for the UE (102).

[0215] FIG. 2B is a sequence diagram that illustrates the proposed method where upon expiry of the timer for disaster return wait range, the UE shall not start a timer with the disaster return wait range value again until the UE selects a PLMN for disaster roaming services, according to embodiments as disclosed herein.

[0216] In an embodiment, at step 1, disaster condition occurs on the second PLMN (104b) (for example, UE (102) determined PLMN with disaster condition is the second PLMN (104b)). At step 2, the UE (102) is registered to the first PLMN (104a) for disaster roaming services. At step 3, disaster condition ends on the second PLMN (104b). At step 4, upon determining that the disaster condition has ended as specified in 3GPP TS 23.122, the UE (102) performs the PLMN selection as specified in 3GPP TS 23.122 and selects UE determined PLMN with disaster condition (for example, the second PLMN (104b)) or any allowable PLMN for normal services. The UE (102) starts a timer generated from disaster return wait range optionally provided by the PLMN providing disaster roaming services (for example, the first PLMN (104a)) or provided by the selected PLMN (for example, the second PLMN (104b)). The UE (102) waits for the expiry of the timer for disaster return wait range. At step 5, after the UE (102) has waited for disaster return wait range duration or upon the expiry of the timer for disaster return wait range, the UE (102) registers on the second PLMN (104b) for the normal services. At step 6, the UE receives a registration reject from the second PLMN (104b) or the registration is not successful on the second PLMN (104b) due to any reasons. At step 7, the UE (102) performs the PLMN selection as specified in 3GPP TS 23.122 and selects same or another allowable PLMN (for example, third PLMN (104c)) for normal services. In an embodiment, the UE (102) may select the second PLMN (104b) again for normal services. At step 8, UE shall not start a timer with the disaster return wait range value again until the UE selects a PLMN for disaster roaming services. For e.g. upon determining that a disaster condition has ended as specified in 3GPP TS 23.122, if the UE (102) receives the REGISTRATION REJECT message while registering for normal services in the UE (102) determined PLMN with disaster condition, the UE shall not use the disaster return wait range value again upon selecting the PLMN after PLMN selection. Upon expiry of the timer for disaster return wait range, the UE shall not start a timer with the disaster return wait range value again until the UE selects a PLMN for disaster roaming services. At step 9, without waiting for the disaster return wait range duration again or without running the timer for the disaster return wait range again, the UE (102) shall immediately perform the registration procedure in the selected PLMN (for example, third PLMN (104c)) for normal services.

[0217] The UE (102) shall perform the below steps in any order or combinations:

[0218] In an embodiment, Upon determining that a disaster condition has ended as specified in 3GPP TS 23.122, If the UE (102) selects the UE-determined PLMN with disaster condition and has a stored disaster return wait range, which is provided by the PLMN providing disaster roaming services or provided by the selected PLMN, the UE (102) shall generate the random number within the disaster return wait range, start a timer with the generated random number value, and enter 5GMM-DEREGISTERED.ATTEMPTING-REGISTRATION state or 5GMM-REGISTERED-ATTEMPTING-REGISTRATION-UPDATE state if registered. While the timer is running, the UE (102) shall not initiate registration on the selected PLMN except if the UE (102) needs to request an emergency PDU session, in which case the UE (102) shall initiate the registration procedure, set the 5GS registration type IE to "emergency registration" in the REGISTRATION REQUEST message, and keep the timer running. Upon expiration of the timer, if the UE (102) does not have an emergency PDU session, the UE shall perform a registration procedure if still camped on the selected PLMN. If the UE (102) has an emergency PDU session when the timer expires, the registration procedure as described in subclause 5.5.1 shall be performed after the release of the emergency PDU session if the UE (102) is still camped on the selected PLMN. Otherwise, the UE (102) shall perform the registration procedure in the selected PLMN.

[0219] In an embodiment, after the disaster condition has ended, if the UE (102) receives the REGISTRATION REJECT message while registering for normal services in the MS determined PLMN with disaster condition, the UE (102) shall not use the disaster return wait range value again upon selecting a PLMN after PLMN selection.

[0220] In an embodiment, after the disaster condition has ended, if the UE (102) receives the REGISTRATION REJECT message while registering for normal services in the UE determined PLMN with disaster condition, the UE (102) shall not use the disaster return wait range value again, upon selecting a PLMN after PLMN selection as specified in 3GPP TS 23.122.

[0221] Upon determining that a disaster condition has ended as specified in 3GPP TS 23.122, if the UE (102) receives a REGISTRATION REJECT message while registering for normal services in the UE determined PLMN with disaster condition, the UE (102) shall not use the disaster return wait range value again, upon selecting a PLMN, after PLMN selection.

[0222] Upon determining that a disaster condition has ended as specified in 3GPP TS 23.122, if the UE receives a REGISTRATION REJECT message while registering for normal services in the UE (102) determined PLMN with disaster condition, the UE (102) shall not use the disaster return wait range value again, upon selecting a PLMN, after PLMN selection as specified in 3GPP TS 23.122.

[0223] Upon expiry of the timer for disaster return wait range, the UE shall not start a timer with the disaster return wait range value again until the UE selects a PLMN for disaster roaming services.

[0224] If the UE (102) receives a REGISTRATION REJECT message while registering for normal services in the UE determined PLMN with disaster condition, the UE (102) shall not use the disaster return wait range value again, upon selecting a PLMN, after PLMN selection, upon determining that a disaster condition has ended as specified in 3GPP TS 23.122.

[0225] In an embodiment, after the disaster condition has ended, if the UE (102) has waited for the timer generated from disaster return wait range (for example, disaster return wait range duration) before registering on the UE determined PLMN with disaster condition or the selected allowable PLMN (PLMN-D1), if the UE (102) receives the REGISTRATION REJECT message while registering for normal services in the UE determined PLMN with disaster condition or in the selected PLMN, the UE (102) shall not use the disaster return wait range value again upon selecting a PLMN after PLMN selection.

[0226] In an embodiment, after the disaster condition has ended, if the UE (102) has waited for the timer generated from disaster return wait range (for e.g. disaster return wait range duration) before registering on the UE (102) determined PLMN with disaster condition or the selected allowable PLMN(PLMN-D1), if the UE (102) receives a REGISTRATION REJECT message while registering for normal services in the UE determined PLMN with disaster condition or in the selected PLMN, the UE (102) shall not use the disaster return wait range value again, upon selecting a PLMN after PLMN selection as specified in 3GPP TS 23.122.

[0227] In an embodiment, Upon determining that a disaster condition has ended as specified in 3GPP TS 23.122, if the UE (102) has waited for the timer generated from disaster return wait range (for e.g. disaster return wait range duration) before registering on the UE (102) determined PLMN with disaster condition or the selected allowable PLMN(PLMN-D1), if the UE (102) receives the REGISTRATION REJECT message while registering for normal services in the UE determined PLMN with disaster condition or in the selected PLMN, the UE (102) shall not use the disaster return wait range value again, upon selecting a PLMN after PLMN selection.

[0228] In an embodiment, after the disaster condition has ended, if the UE (102) has waited for the timer generated from disaster return wait range (for example, disaster return wait range duration) before registering on the UE determined PLMN with disaster condition or the selected allowable PLMN (PLMN-D1), if the UE (102) receives a REGISTRATION REJECT message while registering for normal services in the UE determined PLMN with disaster condition or in the selected PLMN, the UE (102) shall not use the disaster return wait range value again upon selecting the same UE determined PLMN with disaster condition after PLMN selection.

[0229] In an embodiment, after the disaster condition has ended, if the UE (102) has waited for the timer generated from disaster return wait range (for e.g. disaster return wait range duration) before registering on the UE determined PLMN with disaster condition or the selected allowable PLMN(PLMN-D1), if the UE (102) receives a REGISTRATION REJECT message while registering for normal services in the UE determined PLMN with disaster condition or in the selected PLMN, the UE (102) shall not use the disaster return wait range value again, upon selecting the same UE determined PLMN with disaster condition after PLMN selection as specified in 3GPP TS 23.122.

[0230] In an embodiment, upon determining that a disaster condition has ended as specified in 3GPP TS 23.122, if the UE (102) has waited for the timer generated from disaster return wait range (for e.g. disaster return wait range duration) before registering on the UE determined PLMN with disaster condition or the selected allowable PLMN(PLMN-D1), if the UE (102) receives a REGISTRATION REJECT message while registering for normal services in the UE determined PLMN with disaster condition or in the selected PLMN, the UE (102) shall not use the disaster return wait range value again, upon selecting the same UE determined PLMN with disaster condition after PLMN selection as specified in 3GPP TS 23.122.

[0231] In an embodiment, after the disaster condition has ended, optionally if the UE (102) has waited for the timer generated from disaster return wait range (for example, disaster return wait range duration) before registering on the UE determined PLMN with disaster condition or the selected allowable PLMN (PLMN-D1), if the UE (102) receives the REGISTRATION REJECT message while registering for normal services in the UE determined PLMN with disaster condition or in the selected PLMN, the UE shall not use the disaster return wait range value again upon selecting a PLMN (for example, after PLMN selection) other than or different from the UE determined PLMN with disaster condition or the selected PLMN on which UE received the REGISTRATION REJECT message or the registration was not successful.

[0232] In an embodiment, after the disaster condition has ended, if the UE (102) has waited for the timer generated from disaster return wait range (for e.g. disaster return wait range duration) before registering on the UE determined PLMN with disaster condition or the selected allowable PLMN(PLMN-D1), if the UE (102) receives a REGISTRATION REJECT message while registering for normal services in the UE determined PLMN with disaster condition or in the selected PLMN, the UE (102) shall not use the disaster return wait range value again, upon selecting a PLMN (for e.g. after PLMN selection) as specified in 3GPP TS 23.122 other than or different from the UE determined PLMN with disaster condition or the selected PLMN on which UE (102) received the REGISTRATION REJECT message or the registration was not successful.

[0233] In an embodiment, upon determining that a disaster condition has ended as specified in 3GPP TS 23.122, if the UE (102) has waited for the timer generated from disaster return wait range (for e.g. disaster return wait range duration) before registering on the UE (102) determined PLMN with disaster condition or the selected allowable PLMN(PLMN-D1), if the UE (102) receives the REGISTRATION REJECT message while registering for normal services in the UE (102) determined PLMN with disaster condition or in the selected PLMN, the UE (102) shall not use the disaster return wait range value again, upon selecting a PLMN (for e.g. after PLMN selection) other than or different from the UE (102) determined PLMN with disaster condition or the selected PLMN on which UE received the REGISTRATION REJECT message or the registration was not successful.

[0234] In an embodiment, after the disaster condition has ended, optionally if the UE (102) has waited for the timer generated from disaster return wait range (for example, disaster return wait range duration) before registering on the UE (102) determined PLMN with disaster condition or the selected allowable PLMN (PLMN-D1), if the UE (102) receives the REGISTRATION REJECT message while registering for normal services in the UE determined PLMN with disaster condition or in the selected PLMN, the UE (102) shall use the disaster return wait range value again and wait for the disaster return wait range duration upon selecting the PLMN (for example, after PLMN selection) other than or different from the UE (102) determined PLMN with disaster condition or the selected PLMN on which UE (102) received the REGISTRATION REJECT message or the registration was not successful.

[0235] In an embodiment, after the disaster condition has ended, if the UE (102) has waited for the timer generated from disaster return wait range (for e.g. disaster return wait range duration) before registering on the UE determined PLMN with disaster condition or the selected allowable PLMN(PLMN-D1), if the UE (102) receives a REGISTRATION REJECT message while registering for normal services in the UE determined PLMN with disaster condition or in the selected PLMN, the UE (102) shall use the disaster return wait range value again and wait for the disaster return wait range duration, upon selecting a PLMN (for e.g. after PLMN selection) as specified in 3GPP TS 23.122 other than or different from the UE determined PLMN with disaster condition or the selected PLMN on which UE (102) received the REGISTRATION REJECT message or the registration was not successful.

[0236] In an embodiment, upon determining that a disaster condition has ended as specified in 3GPP TS 23.122,if the UE (102) has waited for the timer generated from disaster return wait range (for e.g. disaster return wait range duration) before registering on the UE (102) determined PLMN with disaster condition or the selected allowable PLMN(PLMN-D1), if the UE (102) receives the REGISTRATION REJECT message while registering for normal services in the UE (102) determined PLMN with disaster condition or in the selected PLMN, the UE (102) shall use the disaster return wait range value again and wait for the disaster return wait range duration, upon selecting the PLMN (for e.g. after PLMN selection) other than or different from the UE (102) determined PLMN with disaster condition or the selected PLMN on which UE received the REGISTRATION REJECT message or the registration was not successful.

[0237] The term UE (102) performs PLMN selection refers to PLMN selection procedure as specified in 3GPP TS 23.122

[0238] The procedures and solutions defined in this embodiment for "After the disaster condition has ended" are also applicable for "Upon determining that a disaster condition has ended as specified in 3GPP TS 23.122".

[0239] The procedures and solutions defined in this embodiment for "Upon determining that a disaster condition has ended as specified in 3GPP TS 23.122" are also applicable for " After the disaster condition has ended"

[0240] The terms "MS Determined PLMN with disaster condition" and "UE determined PLMN with disaster condition" are used interchangeably and have the same meaning.

[0241] The solutions explained in this embodiment are explained using Registration Reject as an example. However, the solutions are not restricted to Registration Reject procedure and are also applicable for any procedure when the UE selects a PLMN for disaster roaming services or when the UE selects a PLMN for normal services after disaster condition has ended.

[0242] In an embodiment, upon determining that a disaster condition has ended and that the UE (102) shall perform PLMN selection as specified in 3GPP TS 23.122, if the UE (102) has a stored disaster return wait range and it was not registered on the selected PLMN for normal service and not waited for the time duration of the generated random number within the disaster return wait range (for example, after the disaster condition / situation had ended if the UE (102) was not registered on the selected PLMN for normal service (optionally not even once) and the UE (102) has not waited for the time duration of the generated random number within the disaster return wait range), the UE (102) shall generate a random number within the disaster return wait range and start a timer with the generated random number value. While the timer is running, the UE (102) shall not initiate registration on the selected PLMN except if the UE needs to request an emergency PDU session, in which case the UE (102) shall initiate the registration procedure for emergency services, set the 5GS registration type IE to "emergency registration" in the REGISTRATION REQUEST message or any NAS signaling message, and keep the timer running. Upon expiration of the timer, if the UE (102) does not have an emergency PDU session, the UE (102) shall perform a registration procedure for disaster roaming services if still camped on the selected PLMN. Upon expiration of the timer, if the UE (102) has the emergency PDU session when the timer expires, the UE (102) shall initiate the registration procedure after the release of the emergency PDU session if the UE is still camped on the selected PLMN.

[0243] In an embodiment, upon determining that a disaster condition has ended and that the UE (102) shall perform PLMN selection as specified in 3GPP TS 23.122, if the UE (102) has the stored disaster return wait range optionally for the selected PLMN (or optionally for the selected PLMN and RAT combination) and it was not registered on the selected PLMN (or optionally on the selected PLMN and RAT combination) for the normal service and not waited for the time duration of the generated random number within the disaster return wait range optionally for / on the selected PLMN (or optionally for / on the selected PLMN and RAT combination) (for example, after the disaster condition / situation had ended if the UE (102) was not registered on the selected PLMN or selected PLMN+RAT combination for normal service (optionally not even once) and the UE (102) has not waited for the time duration of the generated random number within the disaster return wait range for / on the selected PLMN or selected PLMN+RAT combination), the UE (102) shall generate the random number within the disaster return wait range and start a timer with the generated random number value.

[0244] While the timer is running, the UE (102) shall not initiate registration on the selected PLMN except if the UE (102) needs to request an emergency PDU session, in which case the UE (102) shall initiate the registration procedure for emergency services, set the 5GS registration type IE to "emergency registration" in the REGISTRATION REQUEST message or any NAS signalling message, and keep the timer running. Upon expiration of the timer, if the UE (102) does not have an emergency PDU session, the UE (102) shall perform a registration procedure for disaster roaming services if still camped on the selected PLMN. Upon expiration of the timer, if the UE (102) has the emergency PDU session when the timer expires, the UE (102) shall initiate the registration procedure after the release of the emergency PDU session if the UE is still camped on the selected PLMN.

[0245] In an embodiment, upon determining that a disaster condition has ended and that the UE (102) shall perform PLMN selection as specified in 3GPP TS 23.122, if the UE (102) has a stored disaster return wait range and it was not registered on the selected PLMN for normal service (for example, after the disaster condition / situation had ended if the UE (102) was not registered on the selected PLMN for normal service, optionally not even once), the UE (102) shall generate a random number within the disaster return wait range and start a timer with the generated random number value. While the timer is running, the UE (102) shall not initiate registration on the selected PLMN except if the UE needs to request an emergency PDU session, in which case the UE (102) shall initiate the registration procedure for emergency services, set the 5GS registration type IE to "emergency registration" in the REGISTRATION REQUEST message or any NAS signalling message, and keep the timer running.

[0246] Upon expiration of the timer, if the UE (102) does not have an emergency PDU session, the UE (102) shall perform a registration procedure for disaster roaming services if still camped on the selected PLMN. Upon expiration of the timer, if the UE (102) has an emergency PDU session when the timer expires, the UE shall initiate the registration procedure after the release of the emergency PDU session if the UE (102) is still camped on the selected PLMN.

[0247] In an embodiment, upon determining that the disaster condition has ended and that the UE (102) shall perform PLMN selection as specified in 3GPP TS 23.122, if the UE (102) has a stored disaster return wait range and it was not registered on the selected PLMN for normal service, optionally if the selected PLMN is MS determined PLMN with disaster condition (for example, PLMN-D) or the PLMN previously with disaster condition (for example, after disaster condition / situation had ended), if the UE (102) was not registered on the selected PLMN for disaster roaming service (optionally not even once) and / or optionally if the selected PLMN is MS determined PLMN with disaster condition (for example, PLMN-D) or the PLMN previously with disaster condition, the UE (102) shall generate a random number within the disaster return wait range and start a timer with the generated random number value. While the timer is running, the UE (102) shall not initiate registration on the selected PLMN except if the UE (102) needs to request an emergency PDU session, in which case the UE (102) shall initiate the registration procedure for emergency services, set the 5GS registration type IE to "emergency registration" in the REGISTRATION REQUEST message or any NAS signaling message, and keep the timer running. Upon expiration of the timer, if the UE does not have an emergency PDU session, the UE (102) shall perform a registration procedure for disaster roaming services if still camped on the selected PLMN. Upon expiration of the timer, if the UE (102) has an emergency PDU session when the timer expires, the UE (102) shall initiate registration procedure after the release of the emergency PDU session if the UE (102) is still camped on the selected PLMN.

[0248] In an embodiment, upon determining that a disaster condition has ended and that the UE (102) shall perform PLMN selection as specified in 3GPP TS 23.122, if the UE (102) has a stored disaster return wait range and UE was previously registered for disaster roaming services (for example, UE (102) is / was not registered for normal services on any PLMN or PLMN and RAT combination) (for example, UE (102) is / was not registered for normal services even once after disaster condition / situation had ended), the UE (102) shall generate a random number within the disaster return wait range and start a timer with the generated random number value. While the timer is running, the UE (102) shall not initiate registration on the selected PLMN except if the UE (102) needs to request an emergency PDU session, in which case the UE (102) shall initiate the registration procedure for emergency services, set the 5GS registration type IE to "emergency registration" in the REGISTRATION REQUEST message or any NAS signaling message, and keep the timer running. Upon expiration of the timer, if the UE (102) does not have an emergency PDU session, the UE (102) shall perform a registration procedure for disaster roaming services if still camped on the selected PLMN. Upon expiration of the timer, if the UE (102) has an emergency PDU session when the timer expires, the UE (102) shall initiate registration procedure after the release of the emergency PDU session if the UE (102) is still camped on the selected PLMN.

[0249] In an embodiment, upon determining that a disaster condition has ended and that the UE (102) shall perform PLMN selection as specified in 3GPP TS 23.122, if the UE (102) has a stored disaster return wait range and UE (102) was previously not registered for normal services, optionally on any PLMN or optionally on any PLMN and RAT combination (for example, UE (102) was not registered for normal services on any PLMN or PLMN and RAT combination) (for example, UE (102) is / was not registered for normal services even once after disaster condition / situation had ended), the UE (102) shall generate a random number within the disaster return wait range and start a timer with the generated random number value. While the timer is running, the UE (102) shall not initiate registration on the selected PLMN except if the UE needs to request an emergency PDU session, in which case the UE (102) shall initiate the registration procedure for emergency services, set the 5GS registration type IE to "emergency registration" in the REGISTRATION REQUEST message or any NAS signalling message, and keep the timer running. Upon expiration of the timer, if the UE (102) does not have an emergency PDU session, the UE (102) shall perform a registration procedure for disaster roaming services if still camped on the selected PLMN. Upon expiration of the timer, if the UE (102) has the emergency PDU session when the timer expires, the UE (102) shall initiate registration procedure after the release of the emergency PDU session if the UE (102) is still camped on the selected PLMN.

[0250] In an embodiment, upon determining that a disaster condition has ended and that the UE (102) shall perform PLMN selection as specified in 3GPP TS 23.122, if the UE (102) has a stored disaster return wait range and UE (102) has not started / run the timer / time duration (for example, the Disaster return wait timer) of generated random number within the disaster return wait range for / on the selected PLMN (or optionally selected PLMN and RAT combination) at least once, optionally after the disaster condition / situation has ended (for example, after disaster condition / situation had ended if the UE (102) has not started / run the time duration of generated random number within the disaster return wait range for / on the selected PLMN or selected PLMN+RAT combination (for example, PLMN-D) even once), the UE (102) shall generate a random number within the disaster return wait range and start a timer with the generated random number value. While the timer is running, the UE (102) shall not initiate registration on the selected PLMN except if the UE (102) needs to request an emergency PDU session, in which case the UE (102) shall initiate the registration procedure for emergency services, set the 5GS registration type IE to "emergency registration" in the REGISTRATION REQUEST message or any NAS signaling message, and keep the timer running. Upon expiration of the timer, if the UE (102) does not have an emergency PDU session, the UE (102) shall perform a registration procedure for disaster roaming services if still camped on the selected PLMN. Upon expiration of the timer, if the UE (102) has an emergency PDU session when the timer expires, the UE (102) shall initiate registration procedure after the release of the emergency PDU session if the UE (102) is still camped on the selected PLMN.

[0251] In an embodiment, upon determining that a disaster condition has ended and that the UE (102) shall perform PLMN selection as specified in 3GPP TS 23.122, if the UE (102) has a stored disaster return wait range and the UE (102) has not started / run the timer / time duration (for example, the Disaster return wait timer) of the generated random number within the disaster return wait range for / on any PLMN (or optionally for / on any PLMN and RAT combination) at least once, optionally after the disaster condition / situation has ended (for example, after the disaster condition / situation had ended if the UE (102) has not started / run the time duration of the generated random number within the disaster return wait range for / on any PLMN (or PLMN and RAT combination) even once), the UE (102) shall generate a random number within the disaster return wait range and start a timer with the generated random number value. While the timer is running, the UE (102) shall not initiate registration on the selected PLMN except if the UE needs to request an emergency PDU session, in which case the UE (102) shall initiate the registration procedure for emergency services, set the 5GS registration type IE to "emergency registration" in the REGISTRATION REQUEST message or any NAS signaling message, and keep the timer running. Upon expiration of the timer, if the UE does not have an emergency PDU session, the UE (102) shall perform a registration procedure for disaster roaming services if still camped on the selected PLMN. Upon expiration of the timer, if the UE (102) has the emergency PDU session when the timer expires, the UE (102) shall initiate the registration procedure after the release of the emergency PDU session if the UE is still camped on the selected PLMN.

[0252] In an embodiment, upon determining that the disaster condition has ended and that the UE (102) shall perform PLMN selection as specified in 3GPP TS 23.122, if the UE (102) has a stored disaster return wait range and the UE has not waited for the timer / time duration (for example, the Disaster return wait timer) (for example, the UE has not waited for the timer to expire or the UE has not executed the full wait timer / time duration) of the generated random number within the disaster return wait range to expire for / on the selected PLMN (or optionally selected PLMN and RAT combination) not even once, optionally after the disaster condition / situation has ended (for example, after the disaster condition / situation had ended if the UE has not waited for the time duration of the generated random number within the disaster return wait range to expire for / on the selected PLMN or selected PLMN+RAT combination (for example, PLMN-D) at least once), the UE shall generate a random number within the disaster return wait range and start a timer with the generated random number value. While the timer is running, the UE shall not initiate registration on the selected PLMN except if the UE needs to request an emergency PDU session, in which case the UE shall initiate the registration procedure for emergency services, set the 5GS registration type IE to "emergency registration" in the REGISTRATION REQUEST message or any NAS signaling message, and keep the timer running. Upon expiration of the timer, if the UE (102) does not have an emergency PDU session, the UE (102) shall perform a registration procedure for disaster roaming services if still camped on the selected PLMN. Upon expiration of the timer, if the UE (102) has the emergency PDU session when the timer expires, the UE shall initiate the registration procedure after the release of the emergency PDU session if the UE (102) is still camped on the selected PLMN.

[0253] In an embodiment, upon determining that a disaster condition has ended and that the UE (102) shall perform PLMN selection as specified in 3GPP TS 23.122, if the UE (102) has the stored disaster return wait range and the UE has not waited for the timer / time duration (for example, the Disaster return wait timer) (for example, the UE has not waited for the timer to expire or the UE (102) has not executed the full wait timer / time duration) of the generated random number within the disaster return wait range to expire for / on any PLMN (or optionally for / on any PLMN and RAT combination) not even once, optionally after the disaster condition / situation has ended (for example, after the disaster condition / situation had ended if the UE has not waited for the time duration of the generated random number within the disaster return wait range to expire for / on any PLMN (or PLMN and RAT combination) at least once), the UE shall generate a random number within the disaster return wait range and start a timer with the generated random number value. While the timer is running, the UE shall not initiate registration on the selected PLMN except if the UE (102) needs to request an emergency PDU session, in which case the UE (102) shall initiate the registration procedure for emergency services, set the 5GS registration type IE to "emergency registration" in the REGISTRATION REQUEST message or any NAS signaling message, and keep the timer running. Upon expiration of the timer, if the UE (102) does not have an emergency PDU session, the UE shall perform a registration procedure for disaster roaming services if still camped on the selected PLMN. Upon expiration of the timer, if the UE (102) has the emergency PDU session when the timer expires, the UE (102) shall initiate the registration procedure after the release of the emergency PDU session if the UE is still camped on the selected PLMN.

[0254] In an embodiment, upon determining that the disaster condition has ended and that the UE (102) shall perform PLMN selection as specified in 3GPP TS 23.122, if the UE (102) has the stored disaster return wait range and the UE is not running any other timers for the selected PLMN (optionally selected PLMN + RAT combination) due to any of the 5GMM or 5GSM reject causes as mentioned in 3GPP TS 24.501, the UE (102) shall generate the random number within the disaster return wait range and start a timer with the generated random number value. While the timer is running, the UE (102) shall not initiate registration on the selected PLMN except if the UE needs to request an emergency PDU session, in which case the UE (102) shall initiate the registration procedure for emergency services, set the 5GS registration type IE to "emergency registration" in the REGISTRATION REQUEST message or any NAS signaling message, and keep the timer running. Upon expiration of the timer, if the UE (102) does not have an emergency PDU session, the UE shall perform a registration procedure for disaster roaming services if still camped on the selected PLMN. Upon expiration of the timer, if the UE (102) has the emergency PDU session when the timer expires, the UE (102) shall initiate the registration procedure after the release of the emergency PDU session if the UE (102) is still camped on the selected PLMN.

[0255] In an embodiment, if the UE (102) was previously camped for normal services on the selected PLMN / PLMN+RAT combination or any of the PLMN / PLMN+RAT combination, or if the UE (102) needs to start / run the disaster return wait range / timer for the selected PLMN (optionally selected PLMN + RAT combination) or any of the PLMN(s) (optionally selected PLMN + RAT combination) after the disaster condition has ended, the UE (102) may optionally start a disaster return wait range / timer with a random value generated between 0 and the difference (i.e., remaining time) of the value between the previously run timer and the current value of the disaster return wait range / timer. if the previously run timer value is more than the current disaster return wait range / timer, or if the difference (i.e., remaining time) between the previously run timer and the current disaster return wait range is less than 0, the UE may optionally not start any timer or may start a wait timer with a random value between 0 and not exceeding the disaster return wait range. For example, if the UE (102) performs PLMN selection and selects another allowable PLMN for normal services when the timer for the disaster return wait range is running or has already run once, the UE (102) shall behave as:

[0256] Let t1 be the time remaining for the timer for disaster return wait range timeout when the UE (102) performed PLMN selection for normal services, and let t be the time elapsed between when the UE performed PLMN selection and selected another allowable PLMN. if t1 is greater than t, then the timer shall be restarted with the value t1 - t. if t1 is equal to or less than t, then the timer need not be restarted. if the UE is not capable of determining t, then the UE shall restart the timer with the value t1.

[0257] In an embodiment, upon determining that a disaster condition has ended and that the UE (102) shall perform PLMN selection as specified in 3GPP TS 23.122, if the UE (102) has a stored disaster return wait range and it was registered on the selected PLMN for normal service and / or the UE has waited for the time duration of the generated random number within the disaster return wait range (for example, after the disaster condition / situation had ended, if the UE was registered on the selected PLMN for normal service (optionally even once) and / or the UE has waited for the time duration of the generated random number within the disaster return wait range), the UE (102) shall NOT generate a random number within the disaster return wait range and shall NOT start a timer with the generated random number value. The UE shall perform a registration procedure or any NAS / AS signaling procedure on the selected PLMN.

[0258] In an embodiment, upon determining that a disaster condition has ended and that the UE (102) shall perform PLMN selection as specified in 3GPP TS 23.122, if the UE (102) has a stored disaster return wait range optionally for the selected PLMN (or optionally for the selected PLMN and RAT combination) and it was registered on the selected PLMN (or optionally on the selected PLMN and RAT combination) for normal service and / or the UE has waited for the time duration of the generated random number within the disaster return wait range optionally for / on the selected PLMN (or optionally for / on the selected PLMN and RAT combination) (for example, after the disaster condition / situation had ended, if the UE was registered on the selected PLMN or selected PLMN+RAT combination for normal service (optionally even once) and / or the UE (102) has waited for the time duration of the generated random number within the disaster return wait range for / on the selected PLMN or selected PLMN+RAT combination), the UE shall NOT generate a random number within the disaster return wait range and shall NOT start a timer with the generated random number value. The UE shall perform a registration procedure or any NAS / AS signaling procedure on the selected PLMN.

[0259] In an embodiment, upon determining that a disaster condition has ended and that the UE (102) shall perform PLMN selection as specified in 3GPP TS 23.122, if the UE (102) has a stored disaster return wait range and it was registered on the selected PLMN for normal service (for example, after the disaster condition / situation had ended, if the UE was registered on the selected PLMN for normal service (optionally even once)), the UE (102) shall NOT generate a random number within the disaster return wait range and shall NOT start a timer with the generated random number value. The UE (102) shall perform a registration procedure or any NAS / AS signaling procedure on the selected PLMN.

[0260] In an embodiment, upon determining that a disaster condition has ended and that the UE (102) shall perform PLMN selection as specified in 3GPP TS 23.122, if the UE (102) has a stored disaster return wait range and it was registered on the selected PLMN for normal service, optionally if the selected PLMN is MS determined PLMN with disaster condition (for example, PLMN-D) or the PLMN previously with disaster condition (for example, after the disaster condition / situation had ended, if the UE was registered on the selected PLMN for disaster roaming service (optionally even once) and / or optionally if the selected PLMN is MS determined PLMN with disaster condition (for example, PLMN-D) or the PLMN previously with disaster condition), the UE shall NOT generate a random number within the disaster return wait range and shall NOT start a timer with the generated random number value. The UE (102) shall perform a registration procedure or any NAS / AS signaling procedure on the selected PLMN.

[0261] In an embodiment, upon determining that a disaster condition has ended and that the UE (102) shall perform PLMN selection as specified in 3GPP TS 23.122, if the UE (102) has a stored disaster return wait range and the UE was previously not registered for disaster roaming services (for example, UE is / was registered for normal services on any PLMN or PLMN and RAT combination) (for example, UE is / was registered for normal services even once after the disaster condition / situation had ended), the UE shall NOT generate a random number within the disaster return wait range and shall NOT start a timer with the generated random number value. The UE (102) shall perform a registration procedure or any NAS / AS signaling procedure on the selected PLMN.

[0262] In an embodiment, upon determining that a disaster condition has ended and that the UE shall perform PLMN selection as specified in 3GPP TS 23.122, if the UE has a stored disaster return wait range and the UE was previously registered for normal services, optionally on any PLMN or optionally on any PLMN and RAT combination (for example, UE was registered for normal services on any PLMN or PLMN and RAT combination) (for example, UE is / was registered for normal services even once after the disaster condition / situation had ended), the UE (102) shall NOT generate a random number within the disaster return wait range and shall NOT start a timer with the generated random number value. The UE (102) shall perform a registration procedure or any NAS / AS signaling procedure on the selected PLMN.

[0263] In an embodiment, upon determining that a disaster condition has ended and that the UE shall perform PLMN selection as specified in 3GPP TS 23.122, if the UE has a stored disaster return wait range and the UE has started / run the timer / time duration (for example, the Disaster return wait timer) of the generated random number within the disaster return wait range for / on the selected PLMN (or optionally selected PLMN and RAT combination) at least once, optionally after the disaster condition / situation has ended (for example, after the disaster condition / situation had ended if the UE (102) has started / run the time duration of the generated random number within the disaster return wait range for / on the selected PLMN or selected PLMN+RAT combination (for example, PLMN-D) even once), the UE shall NOT generate a random number within the disaster return wait range and shall NOT start a timer with the generated random number value. The UE (102) shall perform a registration procedure or any NAS / AS signaling procedure on the selected PLMN.

[0264] In an embodiment, upon determining that a disaster condition has ended and that the UE shall perform PLMN selection as specified in 3GPP TS 23.122, if the UE has a stored disaster return wait range and the UE (102) has started / run the timer / time duration (for example, the Disaster return wait timer) of the generated random number within the disaster return wait range for / on any PLMN (or optionally for / on any PLMN and RAT combination) at least once, optionally after the disaster condition / situation has ended (for example, after the disaster condition / situation had ended if the UE (102) has started / run the time duration of the generated random number within the disaster return wait range for / on any PLMN (or PLMN and RAT combination) even once), the UE (102) shall NOT generate a random number within the disaster return wait range and shall NOT start a timer with the generated random number value. The UE (102) shall perform a registration procedure or any NAS / AS signaling procedure on the selected PLMN.

[0265] In an embodiment, upon determining that a disaster condition has ended and that the UE shall perform PLMN selection as specified in 3GPP TS 23.122, if the UE (102) has a stored disaster return wait range and the UE has waited for the timer / time duration (for example, the Disaster return wait timer) (for example, UE has waited for the timer to expire or UE has executed the full wait timer / time duration) of the generated random number within the disaster return wait range to expire for / on the selected PLMN (or optionally selected PLMN and RAT combination) even once, optionally after the disaster condition / situation has ended (for example, after the disaster condition / situation had ended if the UE has waited for the time duration of the generated random number within the disaster return wait range to expire for / on the selected PLMN or selected PLMN+RAT combination (for example, PLMN-D) at least once), the UE shall NOT generate a random number within the disaster return wait range and shall NOT start a timer with the generated random number value. The UE (102) shall perform a registration procedure or any NAS / AS signalling procedure on the selected PLMN.

[0266] In an embodiment, upon determining that a disaster condition has ended and that the UE (102) shall perform PLMN selection as specified in 3GPP TS 23.122, if the UE (102) has a stored disaster return wait range and the UE has waited for the timer / time duration (for example, the Disaster return wait timer) (for example, the UE (102) has waited for the timer to expire or UE has executed the full wait timer / time duration) of the generated random number within the disaster return wait range to expire for / on any PLMN (or optionally for / on any PLMN and RAT combination) even once, optionally after the disaster condition / situation has ended (for example, after the disaster condition / situation had ended if the UE (102) has waited for the time duration of the generated random number within the disaster return wait range to expire for / on any PLMN (or PLMN and RAT combination) at least once), the UE (102) shall NOT generate a random number within the disaster return wait range and shall NOT start a timer with the generated random number value. The UE (102) shall perform a registration procedure or any NAS / AS signalling procedure on the selected PLMN.

[0267] In an embodiment, upon determining that a disaster condition has ended and that the UE (102) shall perform PLMN selection as specified in 3GPP TS 23.122, if the UE (102) has a stored disaster return wait range and the UE is running any other timers for the selected PLMN (optionally selected PLMN + RAT combination) due to any of the 5GMM or 5GSM reject causes as mentioned in 3GPP TS 24.501, the UE shall NOT generate a random number within the disaster return wait range and shall NOT start a timer with the generated random number value. The UE (102) shall perform a registration procedure or any NAS / AS signalling procedure on the selected PLMN.

[0268] In an embodiment, the terms UE (102) shall not generate a random number, the UE shall not run the timer (for example, any timer such as disaster roaming wait timer or disaster return wait timer), the UE shall not wait for the timer to expire, and the UE (102) shall consider the timer value as Zero (0) are used interchangeably and have the same meaning.

[0269] The solution defined in this embodiment is explained using Switch OFF and Switch ON as an example. The solution is applicable to all / other cases such as when UE is Switched OFF and / or Switch ON, or when UE is switched ON, or when USIM is removed, or when USIM is removed and / or (re)-inserted, or when USIM is inserted, or when the UE (102) is recovering from lack of coverage, and other such cases. The disaster roaming / return wait range stored in the UE (102) as explained in this embodiment can be stored in USIM / ME.

[0270] In an embodiment, the PLMN selected by the UE (102) can be at least one of forbidden PLMN of the UE, allowable PLMN of the UE, registered PLMN (RPLMN) of the UE, MS determined PLMN with disaster condition, and / or PLMN previously with disaster condition. The terms UE determined PLMN with disaster condition and MS determined PLMN with disaster condition are used interchangeably and have the same meaning. The terms disaster return wait range and disaster return wait timer are used interchangeably and have the same meaning. The term disaster return wait timer refers to a random number generated by the UE (102) within the disaster return wait range and a timer which is started with the generated random number value. The terms disaster roaming wait range and disaster roaming wait timer are used interchangeably and have the same meaning. The term disaster roaming wait timer refers to a random number generated by the UE within the disaster roaming wait range and a timer which is started with the generated random number value.

[0271] In an embodiment, the terms UE (102) shall not generate a random number, the UE shall not run the timer (for example, any timer such as disaster roaming wait timer or disaster return wait timer), the UE (102) shall not wait for the timer to expire, and the UE (102) shall consider the timer value as Zero (0) are used interchangeably and have the same meaning.

[0272] The solution defined in this embodiment is explained using Switch OFF and Switch ON as an example. The solution is applicable to other cases such as when USIM is removed, USIM is removed and / or (re)-inserted, USIM is inserted, the UE (102) is recovering from lack of coverage, and other such cases.

[0273] FIG. 3 illustrates a block diagram of the UE (102) in the telecommunication network (100), according to one or more embodiments.

[0274] Examples of the telecommunication network (100) include, but are not limited to, Public Land Mobile Networks (PLMNs) supporting radio access technologies such as 2G, 3G, 4G, 5G, and beyond-5G / 6G, and may further include non-terrestrial network (NTN) access via satellite systems. In addition, the telecommunication network (100) may include, in combination or alternatively, wireless local area networks and machine-type communication networks, wherein the UE (102) performs NAS procedures and associated signaling over one or more access technologies.

[0275] Examples of the UE (102) include, but are not limited to, mobile phones, smartphones, tablets, wearable devices, computing devices, Internet-of-Things (IoT) devices, vehicular platforms supporting vehicle-to-everything (V2X) communications, public safety devices, medical devices, and other equipment capable of executing NAS procedures.

[0276] In an embodiment, the UE (102) comprises a MINT wait timer handling controller (310), a processor (320), a memory (330), and a communicator (340). The processor (320) is operatively coupled to the MINT wait timer handling controller (310), the memory (330), and the communicator (340). The communicator (340) is configured to transmit and receive control-plane signaling including NAS signaling and to support at least one of terrestrial radio access and satellite radio access.

[0277] The UE (102) is configured to communicate, depending on coverage and connectivity, with at least one satellite-based network entity (e.g., an onboard network node or function) and at least one ground-based network entity (e.g., a ground-based core network node or function).

[0278] The MINT wait timer handling controller (310) is implemented as a microcontroller-based circuit arranged to control MINT timer behavior. In one embodiment, the MINT wait timer handling controller (310) comprises a microcontroller core including an instruction decoder and an arithmetic logic unit (ALU), coupled with a non-transitory controller memory storing timer-control firmware, and further coupled with a hardware timer peripheral including at least one programmable counter / tick generator and an interrupt generation circuit. The MINT wait timer handling controller (310) further includes a memory-mapped timer-parameter register set configured to store one or more MINT timer duration values and associated mode / selection parameters, and an interface circuit configured to receive at least an indication and / or a satellite-to-ground connectivity status indication and to provide a timer expiry indication to the processor (320). In operation, the microcontroller executes the timer-control firmware to program the hardware timer peripheral and to control at least one MINT timer by starting, inhibiting, suspending, resuming, or restarting the at least one MINT timer based on the indication and the connectivity status indication, while maintaining protocol-compliant NAS behavior under intermittent connectivity associated with satellite access and telecommunication operation.

[0279] The MINT wait timer handling controller (310) detects the disaster condition. The MINT wait timer handling controller (310) runs the timer for at least one of: the disaster roaming wait range and the disaster return wait range stored at the UE (102). In an embodiment, the MINT wait timer handling controller (310) generates the random number within one of the disaster roaming wait range or the disaster return wait range. In another embodiment, the MINT wait timer handling controller (310) initiates the timer for the time duration corresponding to the generated random number. the timer is started or run upon selecting a PLMN or a combination of PLMN and RAT for disaster roaming or upon determining that the disaster condition has ended in the PLMN or the combination of PLMN and RAT.

[0280] The MINT wait timer handling controller (310) determines whether the timer has expired at least once after at least one of: the disaster condition has started and the disaster condition has ended. In an embodiment, the MINT wait timer handling controller (310) refrains from starting or running the timer within the disaster roaming wait range again until the disaster condition has ended, when the timer for disaster roaming wait range has expired. In an embodiment, the MINT wait timer handling controller (310) prevents generation of another random number within the disaster roaming wait range. In another embodiment, the MINT wait timer handling controller (310) prevents from starting or running the timer with the random number within the disaster roaming wait range until the disaster condition has ended.

[0281] In an embodiment, the MINT wait timer handling controller (310) refrains from starting or running the timer within the disaster return wait range again until the UE (102) selects the PLMN for the disaster roaming service, when the timer for disaster return wait range has expired. In an embodiment, the MINT wait timer handling controller (310) prevents generation of another random number within the disaster return wait range. In another embodiment, the MINT wait timer handling controller (310) prevents from starting or running the timer with the random number within the disaster return wait range until the UE (102) selects the PLMN for the disaster roaming service.

[0282] The MINT wait timer handling controller (310) performs at least one of: the registration procedure, the NAS signaling procedure, and the AS signaling procedure on the selected PLMN without waiting for the duration / timer of the disaster roaming wait range or the disaster return wait range, after the timer has expired at least once.

[0283] The MINT wait timer handling controller (310) is implemented by processing circuitry such as logic gates, integrated circuits, microprocessors, microcontrollers, memory circuits, passive electronic components, active electronic components, optical components, hardwired circuits, or the like. The circuits may, for example, be embodied in one or more semiconductors. The MINT wait timer handling controller (310) implements the solution as described above with respect to FIG. 4.

[0284] The memory (330) stores one of a disaster roaming wait range or a disaster return wait range. The memory (330) is configured to store instructions to be executed by the processor (320). The memory (330) may include non-volatile storage elements. Examples of such non-volatile storage elements may include magnetic hard disks, optical disks, floppy disks, flash memories, or forms of electrically programmable memories (EPROM) or electrically erasable and programmable (EEPROM) memories. In addition, the memory may in some examples be considered a non-transitory storage medium. The term non-transitory may indicate that the storage medium is not embodied in a carrier wave or a propagated signal. However, the term non-transitory should not be interpreted that the memory is non-movable. In some examples, the memory (330) can be configured to store larger amounts of information. In certain examples, a non-transitory storage medium may store data that can over time change (e.g., in Random Access Memory (RAM) or cache).

[0285] The processor (320) communicates with the memory (330), the communicator, and the controller (310). The processor (320) is configured to execute instructions stored in the memory (330) and to perform various processes. The processor (320) may include one or a plurality of processors, 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). The communicator (340) includes an electronic circuit specific to a standard that enables wired or wireless communication. The communicator (340) is configured to communicate internally between internal hardware components of the network system and with external devices via one or more networks.

[0286] FIG. 4 is a flow chart (400) illustrating a method for handling the timer in the telecommunication network (100), according to embodiments as disclosed herein.

[0287] At 402, the method includes detecting the disaster condition. At 404, the method includes running the timer for at least one of: the disaster roaming wait range and the disaster return wait range stored at the UE (100). At 406, the method includes determining whether the timer has expired at least once after at least one of: the disaster condition has started and the disaster condition has ended.

[0288] In an embodiment, at 408, the method includes refraining from starting or running the timer within the disaster roaming wait range again until the disaster condition has ended, when the timer for disaster roaming wait range has expired. In another embodiment, at 410, the method includes refraining, by the UE, from starting or running a timer within the disaster return wait range again until the UE (100) selects the PLMN for the disaster roaming service, when the timer for disaster return wait range has expired.

[0289] At 412, the method includes performing at least one of: the registration procedure, the NAS signaling procedure, and the AS signaling procedure on the selected PLMN without waiting for the duration of the disaster roaming wait range or the disaster return wait range.

[0290] In an embodiment, upon expiry of the timer for the disaster roaming wait range, the UE (102) shall not start the timer with the disaster roaming wait range value again until disaster condition has ended. In another embodiment, upon expiry of the timer for disaster return wait range, the UE (102) shall not start the timer with the disaster return wait range value again until the UE (102) selects the PLMN for disaster roaming services. Hence, the UE (102) gets the disaster roaming / normal services to improve the user experience of the UE without wasting the resource (e.g., signalling resource, bandwidth resource or the like).

[0291] FIG. 5 is a block diagram of a terminal or user equipment (UE) 500 according to an embodiment of the disclosure.

[0292] The terminal is an electronic device capable of wireless communication and having various form factors, examples of the terminal may include a UE, a mobile station (MS), a cellular phone, a smartphone, a computer, a tablet, a wearable device, an Internet of Things (IoT) device, or any other device / system capable of performing wireless communication with a base station (BS) and / or another terminal through a wireless channel.

[0293] Referring to FIG. 5, the UE 500 may include at least one transceiver (hereinafter, referred to as simply "transceiver") 501, at least one processor (hereinafter, referred to as simply "processor") 502, and at least one memory (hereinafter, referred to as simply "memory") 503. According to at least one or a combination of methods corresponding to the embodiments described in the present disclosure, the transceiver 501, the processor 502, and the memory 503 of the UE 500 may operate. However, components of the UE 500 are not limited to the example components illustrated in FIG. 5. In another embodiment, the UE 500 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 501, the processor 502, or the memory 503 may be integrated in the form of one component.

[0294] The transceiver 501 may be a communication circuit or communication circuitry that enables the UE 500 to perform wireless communication with a node or an entity of a network. For example, the transceiver 501 may enable the UE 500 to transmit or receive a signal to or from a BS through cellular communication, or to transmit or receive a signal to or from another UE through cellular communication. For example, the transceiver 501 may support at least one of various cellular communication technologies including 3rd generation (3G), 4th generation (4G), long term evolution (LTE), 5th generation (5G) NR, 6th generation (6G), and various cellular wireless communication technologies supported by the transceiver (501) may include all subsequent generations of evolved wireless communications.

[0295] According to an embodiment, the UE 500 may include a plurality of transceivers. For example, in the case of supporting evolved-universal terrestrial radio access-new radio (E-UTRA-NR) dual connectivity (EN-DC), the UE 500 may include a first transceiver supporting the 4G LTE wireless communication and a second transceiver supporting the 5G NR wireless communication. According to another embodiment, in the case of supporting NR-dual connectivity (NR-DC), the UE 500 may include a plurality of transceivers supporting the 5G NR wireless communication. According to still another embodiment, in the case of supporting near field wireless communication, the UE 500 may separately include a transceiver supporting at least one standard in the group of wireless communication protocol standards as defined in the protocol standards for Bluetooth®, wireless local area network (WLAN) network (including institute of electrical and electronics engineers (IEEE) 802.11-2016 standard or its amendments, e.g., 802.11ah, 802.11ad, 802.11ay, 802.11ax, 802.11az, 802.11ba, and 802.11be, without being limited thereto).

[0296] According to an embodiment, the transceiver 501 may include various circuit structures used to transmit or receive signals to or from a BS through a wireless channel. The signals may include control information and data. For example, the transceiver 501 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 501 may output a signal received through a wireless channel to the processor 502 and may transmit, through a wireless channel, a signal output from the processor 502.

[0297] The processor 502 may control general operations of the UE 500 according to embodiments of the disclosure. The processor 502 may be implemented by one or more integrated circuit (or circuitry) (IC) chips and may execute various data processing operations. The processor 502 may include at least one electric circuit, and may execute instructions (or a program, codes, data, etc.) stored in the memory 503, individually, collectively or in any combination thereof. Further, the processor 502 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.

[0298] The processor 502 may be electrically, operatively, and / or communicatively coupled to the transceiver 501 to control the transceiver 501.

[0299] The processor 502 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. For example, the processor 502 may include a communication processor (CP) configured to control communication operations and an application processor (AP) configured to control execution of an upper layer (for example, an application layer). In a specific embodiment, at least a part of the processor 502 may be included in one chip (or IC) and the other part of the processor 502 may be included in another chip (or IC). Otherwise, at least one processor may be included in another component, for example, the transceiver 501 or the memory 503.

[0300] The processor 502 may perform or control or cause an operation of the UE 500 for executing at least one or a combination of methods according to embodiments of the disclosure. For example, the processor 502 may control operations of the UE 500 for processing a downlink signal received from a BS or generating and transmitting an uplink signal to a BS. To this end, the processor 502 may execute a computer program, codes, or instructions stored in the memory 503, so as to control other components of the UE 500 to enable execution of various operations.

[0301] The memory 503 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 503 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.

[0302] The memory 503 may be electrically, operatively, and / or communicatively coupled to the processor 502 and may be accessed by the processor 502.

[0303] The memory 503 may store a computer program, codes, or instructions executable by the processor 502. According to an embodiment, a computer program, codes, or instructions executable by the processor 502 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 503, the processor 502 may perform various functions according to an embodiment of the disclosure.

[0304] According to an embodiment of the disclosure, operations of the UE 500 may be caused to be performed based on execution of instructions (or a computer program or codes) stored in the memory 503 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.

[0305] FIG. 6 is a block diagram of a base station (BS) 600 according to an embodiment of the disclosure.

[0306] The BS 600 may perform wireless communication with at least one user equipment (UE) located within the area of the BS 600 through a wireless channel. The BS 600 may perform communication with a node or an entity of a network through wired or wireless communication.

[0307] Referring to FIG. 6, the BS 600 may include at least one transceiver (hereinafter, referred to as simply "transceiver") 601, at least one processor (hereinafter, referred to as simply "processor") 602, and at least one memory (hereinafter, referred to as simply "memory") 603. According to at least one or a combination of methods corresponding to the embodiments described in the present disclosure, the transceiver 601, the processor 602, and the memory 603 of the BS 600 may operate. However, components of the BS 600 are not limited to the example components illustrated in FIG. 6. In another embodiment, the BS 600 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 601, the processor 602, or the memory 603 may be integrated in the form of one component.

[0308] The transceiver 601 may be a communication circuit or communication circuitry that enables the BS 600 to perform wireless communication with a node or an entity of a network. For example, the transceiver 601 may enable the BS 600 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 601 may support various cellular communication technologies including 3rd generation (3G), 4th generation (4G), long term evolution (LTE), 5th generation (5G) NR, 6th generation (6G), and various cellular wireless communication technologies supported by the transceiver (601) may include all subsequent generations of evolved wireless communications.. According to an embodiment, the transceiver 601 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 601 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 601 may output a signal received through a wireless channel to the processor 602 and may transmit, through a wireless channel, a signal output from the processor 602.

[0309] Meanwhile, according to an embodiment of the present disclosure, the BS 600 may perform communication with a node or an entity of a network through wired or wireless communication. For example, the BS 600 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. 6, when the BS 600 performs wired communication, the BS 600 may further include a separate network interface for wired communication in addition to the transceiver 601. The network interface may be referred to as network interface circuitry or communication interface circuitry.

[0310] The processor 602 may control general operations of the BS 600 according to embodiments of the disclosure. The processor 602 may be implemented by one or more integrated circuit (or circuitry) (IC) chips and may execute various data processing operations. The processor 602 may include at least one electric circuit, and may execute instructions (or a program, codes, data, etc.) stored in the memory 603, individually, collectively or in any combination thereof. Further, the processor 602 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.

[0311] The processor 602 may be electrically, operatively, and / or communicatively coupled to the transceiver 601 to control the transceiver 601.

[0312] The processor 602 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 602 may be included in one chip (or IC) and the other part of the processor 602 may be included in another chip (or IC). Otherwise, at least one processor may be included in another component, for example, the transceiver 601 or the memory 603.

[0313] The processor 602 may perform or control or cause an operation of the BS 600 for executing at least one or a combination of methods according to embodiments of the disclosure. For example, the processor 602 may control operations of the BS 600 for generating and transmitting a downlink signal to a UE or processing an uplink signal received from a UE. Otherwise, the BS 600 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 602 may execute a computer program, codes, or instructions stored in the memory 603, so as to control other components of the BS 600 to enable execution of various operations.

[0314] The memory 603 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 603 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.

[0315] The memory 603 may be electrically, operatively, and / or communicatively coupled to the processor 602 and may be accessed by the processor 602.

[0316] The memory 603 may store a computer program, codes, or instructions executable by the processor 602. According to an embodiment, a computer program, codes, or instructions executable by the processor 602 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 603, the processor 602 may perform various functions according to an embodiment of the disclosure.

[0317] According to an embodiment of the disclosure, operations of the BS 600 may be caused to be performed based on execution of instructions (or a computer program or codes) stored in the memory 603 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.

[0318] 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.

[0319] The structure of the above-described network entity will be described in more detail with reference to the drawings.

[0320] FIG. 7 is a block diagram of a network entity 700 according to an embodiment of the disclosure.

[0321] The network entity 700 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 700.

[0322] 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.

[0323] 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), etc.

[0324] Referring to FIG. 7, the network entity 700 may include at least one network interface 701, at least one processor 702 (hereinafter, "processor"), and at least one memory 703 (hereinafter, "memory"). As described above, a NF may be implemented in the form of a physical device such as the network entity 700, 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. 7. In such a case, the instance may be logically represented as comprising one or more logical functional elements.

[0325] According to at least one or a combination of methods corresponding to the embodiments described in the present disclosure, the network interface 701, the processor 702, and the memory 703 of the network entity 700 may operate. However, components of the network entity 700 are not limited to the example components illustrated in FIG. 7. In another embodiment, the network entity 700 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 701, the processor 702, or the memory 703 may be integrated in the form of one component.

[0326] The network interface 701 is a collective term for a transmitter part of the network entity 700 and a receiver part of the network entity 700, 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 701 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 701 may operate using various protocols (e.g., non-access stratum (NAS) protocol). The network interface 701 may also be referred to, for convenience of description or depending on implementation, as communication circuitry, network interface circuitry, or a communication interface circuitry.

[0327] The processor 702 may control general operations of the network entity 700 according to embodiments of the disclosure. The processor 702 may be implemented by one or more integrated circuit (or circuitry) (IC) chips and may execute various data processing operations. The processor 702 may include at least one electric circuit, and may execute instructions (or a program, codes, data, etc.) stored in the memory 703, individually, collectively or in any combination thereof. Further, the processor 702 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.

[0328] According to an embodiment, the processor 702 may be electrically, operatively, and / or communicatively coupled to the network interface 701 to control the network interface 701.

[0329] The processor 702 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 702 may be included in one chip (or IC) and the other part of the processor 702 may be included in another chip (or IC). Otherwise, at least one processor may be included in another component, for example, the network interface 701 or the memory 703.

[0330] The processor 702 may perform or control or cause an operation of the network entity 700 for executing at least one or a combination of methods according to embodiments of the disclosure. For example, the processor 702 may control operations of the network entity 700 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 702 may execute a computer program, codes, or instructions stored in the memory 703, so as to control other components of the network entity 700 to enable execution of various operations.

[0331] The memory 703 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 703 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.

[0332] The memory 703 may be electrically, operatively, and / or communicatively coupled to the processor 702 and may be accessed by the processor 702.

[0333] The memory 703 may store a computer program, codes, or instructions executable by the processor 702. According to an embodiment, a computer program, codes, or instructions executable by the processor 702 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 703, the processor 702 may perform various functions according to an embodiment of the disclosure.

[0334] According to an embodiment of the disclosure, operations of the network entity 700 may be caused to be performed based on execution of instructions (or a computer program or codes) stored in the memory 703 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.

[0335] Meanwhile, although specific embodiments of the present disclosure have been described in detail, various modifications may be made without departing from the scope of the present disclosure. Therefore, the scope of the present disclosure should not be limited to the described embodiments, but should be defined by the claims and equivalents thereof.

Claims

A method performed by a user equipment (UE) in a wireless communication, the method comprising:selecting a first public land mobile network (PLMN) for disaster roaming;upon selecting the first PLMN, in case that the UE has stored a disaster roaming wait range, generating a random number within the disaster roaming wait range; andstarting a first timer with the generated random number within the disaster roaming wait range,wherein, while the first timer is running, a registration on the first PLMN is not initiated, except in case that the UE needs to request an emergency PDU session,wherein, in case that the first timer expires, a timer with a value based on the disaster roaming wait range is not started.The method of claim 1,wherein, in case that the first timer expires, a timer with a value based on the disaster roaming wait range is not started, until a disaster condition has ended.The method of claim 1, further comprising:upon determining that a disaster condition has ended, determining a second PLMN;in case that the UE has stored a disaster return wait range, generating a random number within the disaster return wait range; andstarting a second timer with the generated random number within the disaster return wait range,wherein, while the second timer is running, a registration on the second PLMN is not initiated, except in case that the UE needs to request the emergency PDU session,wherein, in case that the second timer expires, a timer with a value based on the disaster return wait range is not started.The method of claim 3,wherein, in case that the second timer expires, a timer with a value based on the disaster return wait range is not started, until the UE selects a third PLMN for disaster roaming services.The method of claim 1,wherein, in the case that the UE needs to request the emergency PDU session while the first timer is running, the UE initiates a registration procedure, sets a 5th generation system (5GS) registration type information element (IE) to emergency registration in a REGISTRATION REQUEST message, and keeps the first timer running.The method of claim 1,wherein, upon expiration of the first timer, in case that the UE does not have the emergency PDU session, a registration procedure for disaster roaming services is performed.The method of claim 1,wherein, in case that the UE has the emergency PDU session when the first timer expires, a registration procedure for disaster roaming services is performed after release of the emergency PDU session.A user equipment (UE) in a wireless communication, the UE comprising:at least one transceiver;at least one processor communicatively coupled to the at least one transceiver; andat least one memory, communicatively coupled to the at least one processor, storing instructions executable by the at least one processor individually or in any combination to cause the UE to:select a first public land mobile network (PLMN) for disaster roaming,upon selecting the first PLMN, in case that the UE has stored a disaster roaming wait range, generate a random number within the disaster roaming wait range, andstart a first timer with the generated random number within the disaster roaming wait range,wherein, while the first timer is running, a registration on the first PLMN is not initiated, except in case that the UE needs to request an emergency PDU session,wherein, in case that the first timer expires, a timer with a value based on the disaster roaming wait range is not started.The UE of claim 8,wherein, in case that the first timer expires, a timer with a value based on the disaster roaming wait range is not started, until a disaster condition has ended.The UE of claim 8, wherein the instructions further cause the UE to:upon determining that a disaster condition has ended, determine a second PLMN,in case that the UE has stored a disaster return wait range, generate a random number within the disaster return wait range, andstart a second timer with the generated random number within the disaster return wait range,wherein, while the second timer is running, a registration on the second PLMN is not initiated, except in case that the UE needs to request the emergency PDU session,wherein, in case that the second timer expires, a timer with a value based on the disaster return wait range is not started.The UE of claim 10,wherein, in case that the second timer expires, a timer with a value based on the disaster return wait range is not started, until the UE selects a third PLMN for disaster roaming services.The UE of claim 8,wherein, in the case that the UE needs to request the emergency PDU session while the first timer is running, the UE initiates a registration procedure, sets a 5th generation system (5GS) registration type information element (IE) to emergency registration in a REGISTRATION REQUEST message, and keeps the first timer running.The UE of claim 8,wherein, upon expiration of the first timer, in case that the UE does not have the emergency PDU session, a registration procedure for disaster roaming services is performed.The UE of claim 8,wherein, in case that the UE has the emergency PDU session when the first timer expires, a registration procedure for disaster roaming services is performed after release of the emergency PDU session.

Images