Methods and systems for handling a timer in disaster conditions in a wireless communication system

Abstract

The disclosure relates to a 5G or 6G communication system for supporting a higher data transmission rate. A UE in case that determining that a disaster condition is ended, selects a first public land mobile network (PLMN), determines whether a disaster return wait range is provided by the selected first PLMN or a second PLMN providing a disaster roaming service, in case that determining that the disaster return wait range is provided by the first PLMN or the second PLMN, generates a random number within the disaster return wait range, and starts a timer with the generated random number.

Description

METHODS AND SYSTEMS FOR HANDLING A TIMER IN DISASTER CONDITIONS IN A WIRELESS COMMUNICATION SYSTEM

[0001] Embodiments disclosed herein relate to wireless communication networks, and more particularly to systems and methods for handling a wait timer during a disaster condition in a wireless communication network.

[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] In a first aspect of the disclosure, provided herein is a method performed by a user equipment (UE) in a wireless communication system, the method comprising: in case that determining that a disaster condition is ended, selecting a first public land mobile network (PLMN); determining whether a disaster return wait range is provided by the selected first PLMN or a second PLMN providing a disaster roaming service; in case that determining that the disaster return wait range is provided by the first PLMN or the second PLMN, generating a random number within the disaster return wait range; and starting a timer with the generated random number.

[0009] In a second aspect of the disclosure, provided herein a user equipment (UE) in a wireless communication system, the UE comprising: a transceiver; and at least one processor coupled to the transceiver and configured to: in case that determining that a disaster condition is ended, select a first public land mobile network (PLMN), determine whether a disaster return wait range is provided by the selected first PLMN or a second PLMN providing a disaster roaming service, in case that determining that the disaster return wait range is provided by the first PLMN or the second PLMN, generate a random number within the disaster return wait range, start a timer with the generated random number.

[0010] Embodiments herein 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 following illustrated drawings. Embodiments herein are illustrated by the way of examples in the accompanying drawings, and in which:

[0011] FIG. 1 shows an example sequence diagram depicting a method illustrating the problem related to the selection of PLMNs by the UE after end of the disaster condition, according to an embodiment of the disclosure;

[0012] FIG. 2 shows a block diagram shows a schematic overview of a wireless network with available PLMNs after the disaster condition ends, according to an embodiment of the disclosure;

[0013] FIG. 3A and 3B show example sequence diagrams for providing service by PLMN using wait timer during the disaster conditions, according to an embodiment of the disclosure;

[0014] FIG. 4 shows an example flowchart showing the UE has stored a Disaster Return Wait Range per PLMN or the Network has configured the Disaster Return Wait Range per PLMN, according to an embodiment of the disclosure;

[0015] FIG. 5 shows an example flowchart explaining the scenarios, if the UE or the network has stored the Disaster Return Wait Range not on a per PLMN basis or the UE or the network has stored only one value of Disaster Return Wait Range, according to an embodiment of the disclosure; and

[0016] FIG. 6 shows a flowchart for a method handling a timer in a disaster condition, according to an embodiment of the disclosure.

[0017] The embodiments herein and the various features and advantageous details thereof are explained more fully with reference to the non-limiting embodiments that are illustrated in the accompanying drawings and detailed in the following description. Descriptions of well-known components and processing techniques are omitted so as to not unnecessarily obscure the embodiments herein. The examples used herein are intended merely to facilitate an understanding of ways in which the embodiments herein may be practiced and to further enable those of skill in the art to practice the embodiments herein. Accordingly, the examples should not be construed as limiting the scope of the embodiments herein.

[0018] For the purposes of interpreting this specification, the definitions (as defined herein) will apply and whenever appropriate the terms used in singular will also include the plural and vice versa. It is to be understood that the terminology used herein is for the purposes of describing particular embodiments only and is not intended to be limiting. The terms "comprising", "having" and "including" are to be construed as open-ended terms unless otherwise noted.

[0019] The words / phrases "exemplary", "example", "illustration", "in an instance", "and the like", "and so on", "etc.", "etcetera", "e.g.,", "i.e.," are merely used herein to mean "serving as an example, instance, or illustration." Any embodiment or implementation of the subject matter described herein using the words / phrases "exemplary", "example", "illustration", "in an instance", "and the like", "and so on", "etc.", "etcetera", "e.g.,", "i.e.," is not necessarily to be construed as preferred or advantageous over other embodiments.

[0020] Embodiments herein may be described and illustrated in terms of blocks which carry out a described function or functions.　These blocks, which may be referred to herein as managers, units, modules, hardware components or the like, are physically implemented by analog and / or digital circuits such as logic gates, integrated circuits, microprocessors, microcontrollers, memory circuits, passive electronic components, active electronic components, optical components, hardwired circuits and the like, and may optionally be driven by a firmware. The circuits may, for example, be embodied in one or more semiconductor chips, or on substrate supports such as printed circuit boards and the like.　The circuits constituting a block may be implemented by dedicated hardware, or by a processor (e.g., one or more programmed microprocessors and associated circuitry), or by a combination of dedicated hardware to perform some functions of the block and a processor to perform other functions of the block.　Each block of the embodiments may be physically separated into two or more interacting and discrete blocks without departing from the scope of the disclosure. Likewise, the blocks of the embodiments may be physically combined into more complex blocks without departing from the scope of the disclosure.

[0021] It should be noted that elements in the drawings are illustrated for the purposes of this description and ease of understanding and may not have necessarily been drawn to scale. For example, the flowcharts / sequence diagrams illustrate the method in terms of the steps required for understanding of aspects of the embodiments as disclosed herein. Furthermore, in terms of the construction of the device, one or more components of the device may have been represented in the drawings by conventional symbols, and the drawings may show only those specific details that are pertinent to understanding the embodiments so as not to obscure the drawings with details that will be readily apparent to those of ordinary skill in the art having the benefit of the description herein. Furthermore, in terms of the system, one or more components / modules which comprise the system may have been represented in the drawings by conventional symbols, and the drawings may show only those specific details that are pertinent to understanding the embodiments so as not to obscure the drawings with details that will be readily apparent to those of ordinary skill in the art having the benefit of the description herein.

[0022] The accompanying drawings are used to help easily understand various technical features and it should be understood that the embodiments presented herein are not limited by the accompanying drawings. As such, the disclosure should be construed to extend to any modifications, equivalents, and substitutes in addition to those which are particularly set out in the accompanying drawings and the corresponding description. Usage of words such as first, second, third etc., to describe components / elements / steps is for the purposes of this description and should not be construed as sequential ordering / placement / occurrence unless specified otherwise.

[0023] A Public Land Mobile Network (PLMN) is an entire network of operators, where each Base Transceiver Station (BTS) is associated with a geographical cell covering a territory of the PLMN. The PLMNs are mobile wireless networks that use earth-based stations. Particularly, during a disaster condition, a user of a User Equipment (UE) may not get a service from the PLMN earlier providing services to the UE. The disaster condition is a condition that a government decides when to initiate and terminate the service; for e.g., a natural the disaster. Thus, when the disaster conditions occur or are applied by the government, the users may have the opportunity to mitigate service interruptions and failures. In that scenario, the UE associated with the user may be registered for the disaster roaming service. If the UE is registered with the disaster roaming services, then such UEs are allowed to register with other available PLMNs for which the disaster condition is not applied.

[0024] In existing systems, Minimization of Service Interruption (MINT) operates to minimize interruption of services faced by the users when a network entity to which the users are subscribed cannot provide the service due to the disaster such as e.g., a fire, by enabling the users to obtain the service on other networks, while at the same time protecting those other networks from congestion. Further, the MINT aims to enable the UE to obtain the service from the PLMN offering the disaster roaming services when the disaster condition applies to the UE's determined PLMN with the disaster conditions. Thereafter, if the UE supports the MINT, an indication of whether the disaster roaming is enabled in the UE, is determined. Upon determination, the network provides applicable lists of the PLMN(s) that can be used in the disaster conditions which may be provided by a Visited PLMN (VPLMN). The one or more lists of PLMN(s), that are provided, are used by the UE during the disaster condition. Also, the disaster roaming wait range and the disaster return wait range are provisioned by the network. Further, if the disaster roaming wait range and the disaster return wait range are available, then they are stored in a non-volatile memory in the UE as specified in annexure C and / or in Section 4.24 in 3GPP Specification: 24.501 and are kept when the UE enters 5th Generation Mobility Management (5GMM)-DEREGISTERED state. Annex C and / or in Section 4.24 in a 3GPP Specification: 24.501 specifies condition under which the indication of whether the disaster roaming is enabled in the UE, the indication of 'applicability of "lists of PLMN(s) to be used in the disaster condition" provided by the VPLMN', the one or more "lists of PLMN(s) to be used in the disaster condition", the disaster roaming wait range and the disaster return wait range stored in the UE are deleted.

[0025] FIG. 1 shows an example sequence diagram depicting a method illustrating the problem related to the selection of the PLMNs by the UE (102) after end of the disaster condition, according to an embodiment of the disclosure. For example, at step 110, consider that the UE (102) may be initially registered or camped to a first PLMN (104) for normal services. At step 112, the UE (102) is configured with the Disaster Roaming Wait Range and the Disaster Return Wait Range by the first PLMN (104). At step 114, in uncertain situations, consider that the disaster condition has occurred at the first PLMN (104). At step 116, when the disaster condition was triggered, the UE (102) selects a second PLMN (106) (for providing the disaster roaming services on behalf of first PLMN, for e.g., first PLMN (104) is the UE determined PLMN with the disaster condition) to camp on for the disaster roaming services. At step 118, the UE (102) starts the wait timer for a random time between '0' and 'Disaster Roaming Wait Range', and registers on the second PLMN (206) after the expiry of the wait timer.

[0026] At step 120, when the UE (102) determines that the disaster condition is ended, the UE (102) may return to the non-disaster / allowable PLMN by performing a PLMN selection. When the UE (102) performs the PLMN search after exiting the disaster condition, the UE (102) may find multiple allowable PLMNs to camp / register upon. The UE (102) selects the PLMN (for e.g., a third PLMN (108)) other than the first PLMN (104) and applies the Disaster Return Wait Range timer. The UE (102) generates the random number value within the disaster return wait range and starts the timer set to the generated random number value before registering on the selected PLMN (for e.g., third PLMN (108)). However, the UE (102) unnecessarily waits for the Disaster Return Wait Range Timer to expire before registering to the PLMN (i.e., selected PLMN, for e.g., third PLMN (108)) which is different from the PLMN (for e.g., first PLMN (104)) that configured the Disaster Return Wait Range for the UE (102).

[0027] In another scenario, the first PLMN (104) (i.e., the UE (102) determined PLMN with the disaster condition) may not have configured any Disaster Return Wait Range for / in the UE (102). The Disaster Return Wait Range may have been configured by any PLMN (for e.g., the third PLMN (108)) other than UE determined PLMN with the disaster condition (i.e., first PLMN (104) or the PLMN with the disaster condition). The UE (102) may have been selected registered to the second PLMN (106) for the disaster roaming services on behalf of the first PLMN (104) (for e.g., the UE determined PLMN with the disaster condition is the first PLMN (104)). When the UE (102) determines that the disaster condition has ended, the UE (102) may select the first PLMN (104) (i.e., the PLMN previous with the disaster condition or the UE (102) determined PLMN with the disaster condition). The UE (102) may apply Disaster Return Wait Range timer (i.e., the UE (102) generates the random number value within the disaster return wait range and starts the timer set to the generated random number value) before registering on the selected PLMN (for e.g., the first PLMN (104)). However, the UE (102) unnecessarily waits for the Disaster Return Wait Range Timer to expire before registering to the PLMN (i.e., selected PLMN, for e.g. the first PLMN (104)) which may be different from the PLMN (for e.g., the third PLMN (108)) which configured the Disaster Return Wait Range for the UE (102).

[0028] Hence, there is a need for an improved system and method for selecting for applying the disaster return wait range, particularly when the UE (102) wants to return to the desired PLMN after the end of the disaster condition. Therefore, there is a need in the art for solutions which will overcome the above-mentioned drawback(s), among others.

[0029] The principal object of embodiments herein is to disclose methods and systems for handling a timer in the disaster conditions in a wireless communication system.

[0030] Another object of embodiments herein is to select a PLMN, upon determining the disaster condition has ended and the UE has a stored a disaster return wait range.

[0031] Another object of embodiments herein is to determine whether the disaster return wait range is configured by at least one of a first PLMN providing the disaster roaming services, and the selected PLMN.

[0032] Another object of embodiments herein is to generate a random number value within the disaster return wait range on determining the disaster return wait range is configured by at least one of the first PLMN providing the disaster roaming services, and the selected PLMN.

[0033] Another object of embodiments herein is to start a timer with the generated random number value.

[0034] Another object of embodiments herein is to initiate the registration procedure on the selected PLMN, if the timer has expired, or the timer has not started.

[0035] Another object of embodiments herein is to stop or not initiate or block a registration procedure on the selected PLMN while the timer is running.

[0036] Another object of embodiments herein is to initiate the registration procedure on the selected PLMN immediately upon determining the disaster return wait range is configured by a PLMN other than the at least one of the first PLMN providing the disaster roaming services, and the selected PLMN.

[0037] Another object of embodiments herein is to initiate a registration procedure on the selected PLMN immediately upon determining the disaster return wait range is not configured.

[0038] Another object of embodiments herein is to set a fifth-generation services (5GS) registration type information element (IE) to "emergency registration" in a registration request message when the UE has to request the emergency PDU session.

[0039] Another object of embodiments herein is to continue the timer running without interruption during the registration procedure for the emergency PDU session.

[0040] Another object of embodiments herein is to initiate the registration procedure for the emergency PDU session when the timer is running.

[0041] Another object of embodiments herein is to determine whether the UE has an ongoing emergency PDU session when the timer expires.

[0042] Another object of embodiments herein is to initiate the registration procedure for the selected PLMN after release of the emergency PDU session, if the UE is still camped on the selected PLMN, on determining the UE has the ongoing emergency PDU session when the timer expires.

[0043] Accordingly, the embodiments herein provide a method for handling a timer in a disaster condition. The method includes selecting by a User Equipment (UE), a Public Land Mobile Network (PLMN), upon determining a disaster condition has ended, wherein the UE has a stored disaster return wait range. The method further includes determining by the UE, whether the disaster return wait range is configured by at least one of a second PLMN providing disaster roaming services, and the selected PLMN. The method further includes generating, by the UE, a random number value within the disaster return wait range on determining the disaster return wait range is configured by at least one of the second PLMN providing disaster roaming services, and the selected PLMN. The method further includes starting by the UE, a timer with the generated random number value.

[0044] Accordingly, the embodiments herein provide a UE including at least one timer handling controller coupled with a transceiver and a processor. The at least one timer handling controller selects a PLMN, upon determining that a disaster condition has ended. The UE has a stored disaster return wait range. The at least one timer handling controller further determines whether the disaster return wait range is configured by at least one of a second PLMN providing disaster roaming services and the selected PLMN. The at least one timer handling controller further generates a random number value within the disaster return wait range on determining the disaster return wait range is configured by at least one of the second PLMN providing disaster roaming services and the selected PLMN. The at least one timer handling controller further starts a timer with the generated random number value.

[0045] 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 at least one embodiment 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 without departing from the spirit thereof, and the embodiments herein include all such modifications.

[0046] The embodiments herein achieve methods and systems for handling a timer in the disaster conditions in wireless communication.

[0047] The proposed method will help the UE to decide whether to run or not run the Disaster Return Wait Range / Timer after the disaster condition has ended and accordingly proceed for registration with the selected PLMN with / without waiting for the timer to expire. Consider, the disaster occurred at 10 o'clock on a first PLMN, thus the UE selected, at 10:01, a second PLMN to receive the disaster roaming service and disaster ends at 11 o'clock. At 11 o'clock i.e. after disaster has ended, if the UE selects the first PLMN, and if the first PLMN has configured disaster return wait range then UE applies disaster return waiting. If the UE selects the PLMN-X and if the PLMN-X has configured disaster return wait range then UE applies disaster return waiting. If the UE selects the PLMN-X or the first PLMN but the PLMN-X or the PLMN-1 has not configured disaster return wait range but the second PLMN has configured the disaster return wait range then the UE applies disaster roaming waiting. Otherwise, the UE does not apply the disaster return wait range.

[0048] Referring now to the drawings, and more particularly to FIGS. 2 through 6, where similar reference characters denote corresponding features consistently throughout the figures, there are shown embodiments.

[0049] The following definitions, terms, and abbreviations have been referred to herein:

[0050] 3GPP: Third Generation Partnership Project

[0051] 5GC: 5G Core

[0052] 5GCN: 5G Core Network

[0053] 5G-GUTI: 5G-Globally Unique Temporary Identifier

[0054] 5GMM: 5G Mobility Management

[0055] 5GS: 5G System

[0056] 5GSM: 5GS Session Management

[0057] AMF: Access and Mobility Management Function

[0058] AS: Access Stratum

[0059] DL: Downlink

[0060] EHPLMN: Equivalent Home Public Land Mobile Network

[0061] EMM: EUTRA Mobility Management

[0062] eNB: Evolved Node-B

[0063] EPLMN: Equivalent Public Land Mobile Network

[0064] EPS: Evolved Packet System

[0065] E-UTRA: Evolved Universal Mobile Telecommunication Access

[0066] EUTRAN: Evolved Universal Mobile Telecommunication Access Network

[0067] FPLMN: Forbidden Public Land Mobile Network

[0068] gNB: Next generation Node-B

[0069] GPRS: General Packet Radio Service

[0070] HPLMN: Home Public Land Mobile Network

[0071] MCC: Mobile Country Code

[0072] ME: Mobile Equipment

[0073] MINT: Minimization of service interruption

[0074] MME: Mobility Management Entity

[0075] MNC: Mobile Network Code

[0076] NAS: Non-Access Stratum

[0077] NG-RAN: Next Generation Radio Access Network

[0078] NPN: Non-Public Networks

[0079] NR: New Radio

[0080] OOS: Out of Service

[0081] PDU: Packet Data Unit

[0082] PLMN ID: Public Land Mobile Network Identity

[0083] QoS: Quality Of Service

[0084] RAT: Radio Access Technology

[0085] RPLMN: Registered Public Land Mobile Network

[0086] SIM: Subscriber Identity Module

[0087] TAC: Tracking Area Code

[0088] TAI: Tracking Area Identity

[0089] TAU: Tracking Area Update

[0090] UDM: Unified Data Management Function

[0091] UE: User Equipment

[0092] MS: Mobile station

[0093] UL: Uplink

[0094] UPU: UE Parameters Update

[0095] USIM: Universal Subscriber Identification Module

[0096] VPLMN: Visited Public Land Mobile Network

[0097] Visited PLMN (VPLMN): This is a PLMN different from the HPLMN (if the EHPLMN list is not present or is empty) or different from an EHPLMN (if the EHPLMN list is present).

[0098] 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 GPRS service" in the MS.

[0099] Available PLMN: PLMN(s) in the given area which is / are broadcasting capability to provide wireless communication services to the UE.

[0100] Camped on a cell: The MS (ME if there is no SIM) has completed the cell selection / reselection process and has chosen a cell from which it plans to receive all available services. Note that the services may be limited, and that the PLMN or the Standalone Non-Public Network (SNPN) may not be aware of the existence of the MS (ME) within the chosen cell.

[0101] EHPLMN: Any of the PLMN entries contained in the Equivalent HPLMN list.

[0102] Home PLMN: This is the PLMN where the MCC and MNC of the PLMN identity match the MCC and MNC of the International Mobile Subscriber Identity (IMSI).

[0103] Registered PLMN (RPLMN): This is the PLMN on which certain LR (location registration which is also called as registration procedure) outcomes have occurred. In the shared network, the RPLMN is the PLMN defined by the PLMN identity of the CN operator that has accepted the LR.

[0104] Registration: This is the process of camping on a cell of the PLMN or the SNPN and doing any necessary LRs.

[0105] Disaster Condition: This is the condition that a government decides when to initiate and terminate, e.g. the natural the disaster. When this condition applies, users may have the opportunity to mitigate service interruptions and failures.

[0106] 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 the Disaster Condition, and (b) is able to register with other PLMNs.

[0107] Disaster Roaming: This is the special roaming policy that applies during the Disaster Condition.

[0108] PLMN with Disaster Condition: A PLMN to which the Disaster Condition applies.

[0109] Registered for the disaster roaming services: A UE is considered as "registered for the disaster roaming services" when it has successfully completed initial registration or mobility registration for the disaster roaming services.

[0110] Example list of NAS messages may include but are not limited to a REGISTRATION REQUEST message; DEREGISTRATION REQUEST message; a SERVICE REQUEST message; CONTROL PLANE SERVICE REQUEST; IDENTITY REQUEST; AUTHENTICATION REQUEST; AUTHENTICATION RESULT; AUTHENTICATION REJECT; REGISTRATION REJECT; DEREGISTRATION ACCEPT; SERVICE REJECT; SERVICE ACCEPT; UE CONFIGURATION UPDATE command; UE PARAMETERS UPDATE command; and so on.

[0111] The term RAT as defined in an embodiment may be one of the following: NG-RAN, 5G, 4G, 3G, 2G, EPS, 5GS, NR, NR in unlicensed bands, NR (LEO) satellite access, NR (MEO) satellite access, NR(GEO) satellite access, NR (OTHERSAT) satellite access, NR RedCap, E-UTRA, E-UTRA in unlicensed bands, NB-IoT, WB-IoT, LTE-M, and so on.

[0112] The term 5GMM sublayer states in the embodiment are at least one of the below:

[0113] 1. 5GMM-NULL

[0114] 2. 5GMM-DEREGISTERED

[0115] a. 5GMM-DEREGISTERED.NORMAL-SERVICE

[0116] b. 5GMM-DEREGISTERED.LIMITED-SERVICE

[0117] c. 5GMM-DEREGISTERED.ATTEMPTING-REGISTRATION

[0118] d. 5GMM-DEREGISTERED.PLMN-SEARCH

[0119] e. 5GMM-DEREGISTERED.NO-SUPI

[0120] f. 5GMM-DEREGISTERED.NO-CELL-AVAILABLE

[0121] g. 5GMM-DEREGISTERED.eCALL-INACTIVE

[0122] h. 5GMM-DEREGISTERED. INITIAL-REGISTRATION-NEEDED

[0123] 3. 5GMM-REGISTERED-INITIATED

[0124] 4. 5GMM-REGISTERED

[0125] a. 5GMM-REGISTERED.NORMAL-SERVICE

[0126] b. 5GMM-REGISTERED.NON-ALLOWED-SERVICE

[0127] c. 5GMM-REGISTERED.ATTEMPTING-REGISTRATION-UPDATE

[0128] d. 5GMM-REGISTERED.LIMITED-SERVICE

[0129] e. 5GMM-REGISTERED.PLMN-SEARCH

[0130] f. 5GMM-REGISTERED.NO-CELL-AVAILABLE

[0131] g. 5GMM-REGISTERED.UPDATE-NEEDED

[0132] 5. 5GMM-DEREGISTERED-INITIATED

[0133] 6. 5GMM-SERVICE-REQUEST-INITIATED

[0134] In an embodiment herein, the term EMM sublayer states are at least one of the below:

[0135] 1) EMM-NULL

[0136] 2) EMM-DEREGISTERED

[0137] a) EMM-DEREGISTERED.NORMAL-SERVICE

[0138] b) EMM-DEREGISTERED.LIMITED-SERVICE

[0139] c) EMM-DEREGISTERED.ATTEMPTING-TO-ATTACH

[0140] d) EMM-DEREGISTERED.PLMN-SEARCH

[0141] e) EMM-DEREGISTERED.NO-IMSI

[0142] f) EMM-DEREGISTERED.ATTACH-NEEDED

[0143] g) EMM-DEREGISTERED.NO-CELL-AVAILABLE

[0144] h) EMM-DEREGISTERED.eCALL-INACTIVE

[0145] 3) EMM-REGISTERED-INITIATED

[0146] 4) EMM-REGISTERED

[0147] a) EMM-REGISTERED.NORMAL-SERVICE

[0148] b) EMM-REGISTERED.ATTEMPTING-TO-UPDATE

[0149] c) EMM-REGISTERED.LIMITED-SERVICE

[0150] d) EMM-REGISTERED.PLMN-SEARCH

[0151] e) EMM-REGISTERED.UPDATE-NEEDED

[0152] f) EMM-REGISTERED.NO-CELL-AVAILABLE

[0153] g) EMM-REGISTERED.ATTEMPTING-TO-UPDATE-MM

[0154] h) EMM-REGISTERED.IMSI-DETACH-INITIATED

[0155] 5) EMM-DEREGISTERED-INITIATED

[0156] 6) EMM-TRACKING-AREA-UPDATING-INITIATED

[0157] 7) EMM-SERVICE-REQUEST-INITIATED

[0158] The solutions which are defined for NR (5GC) in the disclosure are also applicable to legacy Radio Access Technology (RAT) like E-UTRA / LTE, the corresponding CN entities needs to be replaced by Long Term Evolution (LTE) entities for e.g. Access and Mobility Management Function (AMF) with Mobility Management Entity (MME), Next generation Node-B (gnodeB) with evolved-nodeB (e-nodeB), UDM with HSS etc. But principles of the solution remain same. An example list of NAS messages can be, but not limited to, REGISTRATION REQUEST message; DEREGISTRATION REQUEST message; SERVICE REQUEST message; CONTROL PLANE SERVICE REQUEST; IDENTITY REQUEST; AUTHENTICATION REQUEST; AUTHENTICATION RESULT; AUTHENTICATION REJECT; REGISTRATION REJECT; DEREGISTRATION ACCEPT; SERVICE REJECT; SERVICE ACCEPT, and so on.

[0159] The Network used in an embodiment of the disclosure is explained using any 5G Core Network Function for e.g. AMF. However, the network could be any 5G / EUTRAN Core Network Entities like AMF / SMF / MME / UPF or the Network could be any 5G / EUTRAN RAN Entity like eNodeB (eNB) or gNodeB (gNB) or NG-RAN etc. The messages used or indicated in an embodiment of the disclosure are shown as an example. The messages could be any signaling messages between the UE and the Network Functions / Entities or between different Network functions / entities. The term area / location / geographical area are used in an embodiment may refer to any of cell / cell ID, Tracking Are Code (TAC) / Tracking Are Identity (TAI), Public Land Mobile Network (PLMN), Mobile Country Code (MCC) / Mobile Network Code (MNC), Latitude / longitude, CAG cell or any geographical location / coordinate.

[0160] The terms camp and register are used interchangeably and have the same meaning. The term area as used in an 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.

[0161] The terms wait timer, timer, random timer, the disaster return wait range timer and the disaster return wait timer are used interchangeably and have the same meaning.

[0162] For the list of possible NAS messages, refer to 3GPP TS 24.501 or 3GPP TS 24.301, for list of AS messages refer to 3GPP TS 38.331 or 3GPP TS 36.331. The cause names in an embodiment are for illustration purpose and it can have any name. The Non-Access Stratum (NAS) messages and Access Stratum (AS) messages described in an embodiment is only for illustration purpose it can be any NAS or AS messages as per defined protocol between UE and AMF / MME or UE and gNB (NG-RAN / any RAN node) / eNB.

[0163] In an embodiment of the disclosure, the terms the disaster-based service, the disaster roaming service and the disaster inbound roaming are used interchangeably and have the same meaning.

[0164] In an embodiment of the disclosure, the terms the disaster situation and the disaster condition are used interchangeably and have the same meaning.

[0165] In an embodiment of the disclosure, the terms PLMN D and PLMN-D are used interchangeably and have the same meaning.

[0166] In an embodiment of the disclosure, the terms PLMN A and PLMN-A are used interchangeably and have the same meaning.

[0167] In an embodiment of the disclosure, the terms UE and MS are used interchangeably and have the same meaning.

[0168] In an embodiment of the disclosure, the terms the disaster return wait range and the disaster return wait timer are used interchangeably.

[0169] In an embodiment of the disclosure, 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 the 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 the "the disaster roaming initial registration" and the "the disaster roaming mobility registration updating" in the REGISTRATION REQUEST message.

[0170] In an embodiment of the disclosure, the term area / location / geographical area may refer to any of cell / cell ID, TAC / TAI, PLMN, MCC / MNC, latitude / longitude, CAG cell or any geographical location / coordinate.

[0171] In an embodiment of the disclosure, the disclosure may be applicable to any (but not limited to) Radio Access Technology (RATs).

[0172] In an embodiment of the disclosure, the network used may be any, but not limited to, 5G / EUTRAN core network entities like AMF / SMF / 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.

[0173] FIG. 2 shows a block diagram shows a schematic overview of a wireless network 200 with available PLMNs after the disaster condition ends, according to an embodiment of the disclosure. The wireless network (200) can be, for example, but not limited to a fourth-generation wireless network, a fifth-generation wireless network, Open Radio Access Network (ORAN), a 6G network or the like. The wireless network (200) includes one or more UEs (202) and one or more network entities (NE). The network entity may be a PLMN or an SNPN. The UE (202) may be, for example, but not limited to a laptop, a smart phone, a desktop computer, a notebook, a Device-to-Device (D2D) device, a vehicle to everything (V2X) device, a foldable phone, a smart TV, a tablet, a television, a connected car, an immersive device, an internet of things (IOT) device, or any other device that can communicate using the wireless network.

[0174] In an embodiment of the disclosure, the UE (202) comprises a processor (212), a timer handling controller (214), a transceiver (210), and a memory (216). In an embodiment of the disclosure, the timer handling controller (214) is a part of the processor (212), where the timer handling controller (214) communicates with the network entities (PLMN) through the transceiver (210). In an embodiment of the disclosure, the timer handling controller (214) is outside the processor (212) but the timer handling controller (214) is in communication with the processor (212), where the timer handling controller (214) communicates with the PLMNs through the transceiver (210). In an embodiment of the disclosure, the timer handling controller (214) is outside the processor (212), and the timer handling controller (214) works separately from the processor (212), where the timer handling controller (214) communicates with the PLMNs through the transceiver (210).

[0175] In an embodiment of the disclosure, the memory (216) is configured to store instructions to be executed by the processor (212). The memory (216) can include non-volatile storage elements. Examples of such non-volatile storage elements may include magnetic hard discs, optical discs, floppy discs, flash memories, or forms of electrically programmable memories (EPROM) or electrically erasable and programmable (EEPROM) memories. In addition, the memory (216) 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 an embodiment of the disclosure, the memory (216) is configured to store larger amounts of information. In an embodiment of the disclosure, a non-transitory storage medium may store data that can, over time, change (e.g., in Random Access Memory (RAM) or cache).

[0176] The processor (212) may include one or a plurality of processors. The one or the plurality of processors may be a general-purpose processor, such as a central processing unit (CPU), an application processor (AP), or the like, a graphics-only processing unit such as a graphics processing unit (GPU), a visual processing unit (VPU), and / or an AI-dedicated processor such as a neural processing unit (NPU). The processor (212) may include multiple cores and is configured to execute the instructions stored in the memory (216).

[0177] In an embodiment of the disclosure, the transceiver (210) includes an electronic circuit specific to a standard that enables wired or wireless communication. The transceiver (210) is configured to communicate internally between internal hardware components of the UE (202) and with external devices via one or more networks.

[0178] Embodiments herein disclose systems and methods for providing service by the PLMN using the wait timer idea during the disaster conditions. In an embodiment of the disclosure, initially, consider the user equipment (UE) (202) is registered with the first PLMN (204) for normal services. Further, the network configures the disaster roaming wait range and the disaster return wait range. Thereafter, when the disaster condition hits the first PLMN (204), the UE (202) may wait for a disaster roaming wait timer duration for getting registered with an alternate PLMN, say for example a second PLMN (206). Furthermore, when the disaster condition ends, the UE (202) may perform the PLMN search and finds or selects the first PLMN (204) again. Further, the UE (202) may determine whether the disaster return wait range is configured by at least one of the second PLMN (206) providing the disaster roaming services and the selected PLMN (in this case the first PLMN (204)). The UE (202) may generate a random number value within the disaster return wait range, on determining the disaster return wait range is configured by at least one of the second PLMN (206) providing the disaster roaming services and the selected PLMN. Upon selecting the first PLMN (204), the UE (202) starts wait timer with the generated random number value (any value between 0 and Disaster return wait range) for the first PLMN (204) before registering on the first PLMN (204) if the first PLMN (204) has configured the UE with a Disaster Return Wait Range or there is a Disaster Return Wait Range stored in the UE (202) for the first PLMN (204). Once the timer expires, the UE (202) registers with the first PLMN (204).

[0179] In an embodiment of the disclosure, when the disaster condition occurred at the first PLMN (204) which is servicing the UE (202), and when the disaster condition has ended, then the UE (202) performs PLMN search and finds a third PLMN (208) for providing the service. In such scenarios, the UE (202) does not need to start the wait timer. The UE (202) may immediately camp or register on the third PLMN (208) to receive further services. Hence, in the subject matter, the unnecessary waiting time by the UE (202) is reduced for receiving service from the PLMN which was not facing the disaster condition. Thus, the enablement of providing the services by the PLMN to the UE during the disaster condition is enhanced.

[0180] In an embodiment of the disclosure, the disaster return wait range is the range used to generate the random number value for which the UE (202) waits before attempting to initiate the registration procedure on any of the PLMN. The disaster return wait range includes a minimum wait time, and a maximum wait time.

[0181] In an embodiment of the disclosure, the first PLMN (204) is subject to the disaster that is the first PLMN (204) is the PLMN with the disaster condition, and the second PLMN (206) is alive and not subject to the disaster. The second PLMN (206) may provide the disaster roaming service to the users of the first PLMN (204) (i.e., to the Disaster Inbound roamers of the first PLMN (204)).

[0182] In an embodiment of the disclosure, the UE (202) determines that there is no disaster return wait range that is configured for the selected PLMN or the PLMN providing the disaster roaming services. Based on the determination, the UE (202) initiates the registration procedure on the selected PLMN immediately after the disaster condition has ended. If there is no disaster wait range configured, the timer is not started as no random number value is generated by the UE (202).

[0183] In an embodiment of the disclosure, the UE (202) determines that the UE (202) has to request the emergency PDU session, when the disaster wait range timer is running. The UE (202) sets a fifth-generation services (5GS) registration type information element (IE) to an "emergency registration" in the registration request message. The UE (202) initiates the registration procedure for the emergency PDU session on the selected PLMN. The UE (202) continues the timer running without interruption during the registration procedure for the emergency PDU session.

[0184] In an embodiment of the disclosure, the UE (202) shall wait until the release of the emergency PDU session, if the UE (202) determines that there is the ongoing emergency PDU session on the selected PLMN when the disaster wait range timer expires. The UE (202) shall initiate the registration procedure for the selected PLMN after release of the emergency PDU session, if the UE (202) is still camped on the selected PLMN.

[0185] FIG. 3A and 3B show example sequence diagrams for providing service by the PLMN using the wait timer during the disaster conditions, according to an embodiment of the disclosure.

[0186] The disclosure describes a system and a method for providing service by PLMN using the wait timer during the disaster conditions. For example, as shown in FIG. 3A and FIG. 3B, at step 302, initially, the UE (202) may be registered with the first PLMN (204) for the normal services. Further, at step 304, the network (for example the first PLMN (204)) may configure the disaster roaming wait range and the disaster return wait range for the UE (202).

[0187] In an embodiment of the disclosure, the network may be required to configure Disaster Return Wait Timer for the UE (202) per PLMN. Optionally, the configuration can be performed on the per PLMN and optionally per RAT basis as well. In an embodiment of the disclosure, the UE (202) may receive the "Disaster Return Wait Timer" in the NAS message like registration accept or the UE configuration update message or any other AS / NAS signaling message. Thereafter, the UE (202) may store the Disaster Return Wait Timer / Disaster Return Wait range along with associated PLMN ID (optionally per PLMN-ID+RAT combination). The number of such entries in the UE (202) may be configured by the UE implementation or can be configured by the network.

[0188] In an embodiment of the disclosure, the network may configure the disaster roaming wait range on per PLMN basis and optionally combination of per PLMN and RAT basis. At step 306, in the uncertain situations, consider that the disaster condition has occurred at the first PLMN (204). At step 308, when the disaster condition ends, and the UE (202) selects the PLMN, it applies the timer (the disaster roaming wait range) configured for / by the selected PLMN (optionally PLMN+RAT combination). If the timer was not configured per PLMN basis, then UE (202) applies the default (the disaster roaming wait range) timer value if configured by the network.

[0189] In an embodiment of the disclosure, consider, when the first PLMN (204) faces the disaster condition, then the UE (202) may wait for the disaster roaming wait time duration. After the disaster condition ends, when the UE (202) finds and selects any PLMN (and optionally respective RAT) after performing PLMN search, the UE (202) may apply respective Disaster Return Wait Range value stored for that PLMN or PLMN+RAT combination, and start the timer based on the disaster return wait range value. Also, the network may optionally provide the default Disaster Return Wait Range value, which may be applicable to all PLMNs for which the Disaster Return Wait Range may not be configured by the network. From the selected the disaster return wait range value / the disaster return wait timer value, the UE (202) may select or generate the random value between zero and the disaster return wait range value and starts the wait timer with that value. At step 310, upon the expiry of the wait time duration, the UE (202) may register with the selected PLMN.

[0190] For example, the UE (202) may select and register with the second PLMN (206) for receiving the services during the disaster at the first PLMN (204). Once the disaster ends, the UE (202) may select an appropriate PLMN for getting the service. The UE (202) selects the PLMN after returning from the disaster condition, and checks whether the PLMN ID or PLMN+RAT combination which configured the Disaster Return Wait Range to the UE (202). In an embodiment of the disclosure, if the PLMN ID or PLMN+RAT combination of selected PLMN is same as the PLMN which configured the Disaster Return Wait Range, then the UE (202) may generate the random timer value between 0 and Disaster Return Wait Range. Further, the UE (202) may trigger Non-Access Stratum (NAS) signaling for e.g., registration message on the PLMN on expiration of the timer.

[0191] In an embodiment of the disclosure, referring to FIG. 3B, at step 312, upon determining that the disaster condition has ended and the UE (202) selects the PLMN, the UE (202) doesn't select the PLMN previously with the disaster condition that is the UE (202) does not select the UE (202) determined PLMN with the disaster condition (for e.g., the first PLMN (204)) and the UE (202) selects any PLMN (for e.g., the third PLMN (208)) other than the UE determined PLMN with the disaster condition). At step 314, on determining that the selected PLMN (for e.g., the third PLMN (208)) had NOT configured the disaster return wait range then the UE (202) shall not generate the random number value within the disaster return wait range and shall not start the timer with the generated random number value. The UE (202) shall not wait for any timer and initiate the registration procedure immediately.

[0192] In an embodiment of the disclosure, consider if the selected PLMN or PLMN+RAT combination after returning from the disaster condition is different from the PLMN or PLMN+RAT combination which configured the Disaster Return Wait Timer, i.e., there is no configuration available with the UE (202) for the selected PLMN or PLMN+RAT combination. Then, the UE (202) may not start the timer based on Disaster Return Wait Range. The UE (202) may trigger registration to the selected PLMN immediately. Since the wait timer is configured by different PLMN or PLMN+RAT combination (and not configured by selected PLMN or PLMN+RAT combination) other than the PLMN providing the disaster roaming services and the selected PLMN, the timer value may not be applicable to the selected PLMN (or current / selected PLMN+RAT combination) or it may be considered as value ZERO (0). Hence, the unnecessary waiting time by the UE (202) is reduced and the PLMN is immediately assigned to the UE (202). Furthermore, in an embodiment of the disclosure, the above timer can be optionally started by UE (202) per RAT. Particularly, the timer may be applicable only when the selected PLMN and RAT is same as the PLMN and RAT which configured in Disaster Roaming Wait Range and Disaster Return Wait Range values by the UE (202). In an embodiment of the disclosure, after the disaster condition has ended, the UE (202) selects the UE determined PLMN with the disaster condition. If UE determined PLMN with the disaster condition had configured the disaster return wait range then the UE (202) shall generate the random number value within the disaster return wait range and start the timer with the generated random number value.

[0193] In an embodiment of the disclosure, after the disaster condition has ended, the UE (202) selects the UE determined PLMN with the disaster condition and if the UE determined PLMN with the disaster condition had NOT configured the disaster return wait range then, the UE (202) shall NOT generate the random number value within the disaster return wait range and shall NOT start the timer with the generated random number value.

[0194] In an embodiment of the disclosure, after the disaster condition has ended, the UE (202) does not select the UE determined PLMN with the disaster condition. If the UE determined PLMN with the disaster condition had configured the disaster return wait range then the UE (202) shall not generate the random number value within the disaster return wait range and shall not start the timer with the generated random number value.

[0195] In an embodiment of the disclosure, after the disaster condition has ended, the UE (202) does not select the UE determined PLMN with the disaster condition. If the UE determined PLMN with the disaster condition had NOT configured the disaster return wait range then the UE (202) shall generate the random number value within the disaster return wait range. The UE (202) shall start the timer with the generated random number value if the UE (202) selects the same PLMN which had actually configured in the UE the disaster return wait range.

[0196] The UE (202) shall perform any of the above steps in any order or combinations: Therefore, for example, the UE (202) is configured or has the stored value of the disaster return wait range from the PLMN-X then after the disaster condition has ended, if the UE (202) selects the PLMN-X then UE shall generate the random number value within the disaster return wait range and start the timer with the generated random number value. Otherwise, the UE (202) does not generate the random number value within the disaster return wait range and does not start the timer with the generated random number value.

[0197] In an embodiment of the disclosure, the disaster return wait range is configured or stored in the PLMN, implies that the UE (202) received the disaster return wait range from the PLMN in one of the NAS message like registration accept or UE configuration command etc., or the AS message.

[0198] In an embodiment of the disclosure, the UE (202), upon determining that the disaster condition has ended and selecting the PLMN, the UE (202) selects the PLMN previously with the disaster condition (for e.g., the first PLMN (204)) (i.e., the UE determined PLMN with the disaster condition for e.g., the first PLMN (204)).If the UE determined PLMN with the disaster condition had configured the disaster return wait range then the UE (202) shall generate the random number value within the disaster return wait range and start the timer with the generated random number value.

[0199] In an embodiment of the disclosure, the UE (202), upon determining that the disaster condition has ended and selecting the PLMN, if the UE selects the PLMN previously with the disaster condition (for e.g., the first PLMN (204) that is the UE determined PLMN with the disaster condition. If the UE determined PLMN with the disaster condition had NOT configured the disaster return wait range then the UE (202) shall NOT generate the random number value within the disaster return wait range and shall NOT start the timer with the generated random number value.

[0200] In an embodiment of the disclosure, the UE (202), upon determining that the disaster condition has ended and selecting the PLMN, the UE (202) doesn't select the PLMN previously with the disaster condition that is the UE (202) does not select the UE determined PLMN with the disaster condition (for e.g., the first PLMN (204)) and the UE (202) selects any PLMN (for e.g., the third PLMN (208)) other than the UE determined PLMN with the disaster condition. On determining that the selected PLMN (for e.g., the third PLMN (208)) had NOT configured the disaster return wait range then the UE (202) shall not generate the random number value within the disaster return wait range and shall not start the timer with the generated random number value.

[0201] In an embodiment of the disclosure, the UE (202), upon determining that the disaster condition has ended and selecting the PLMN, the UE (202) doesn't select the PLMN previously with the disaster condition (i.e., the UE doesn't select the UE determined PLMN with the disaster condition (for e.g., the first PLMN (204)) and the UE selects any PLMN (for e.g., the third PLMN (208)) other than the UE determined PLMN with the disaster condition). On determining the selected PLMN (for e.g., the third PLMN (208)) had configured the disaster return wait range then the UE (202) shall generate the random number value within the disaster return wait range and shall start the timer with the generated random number value if the UE selects the same PLMN which had previously configured the disaster return wait range in the UE (202).

[0202] In summary, the UE (202), upon determining that the disaster condition has ended and selecting the PLMN (the third PLMN (208)), shall check if the UE (202) is configured or has the stored value of the disaster return wait range from the third PLMN (208) or not. On determining the UE (202) is configured or has the stored value of the disaster return wait range from the third PLMN (208), then UE (202) shall generate the random number value within the disaster return wait range. The UE (202) shall start the timer with the generated random number value. While the timer is running, the UE (202) shall not initiate registration with the exception of performing an initial registration for emergency services, in the selected PLMN. If performing an initial registration for emergency services in the selected PLMN, the UE (202) shall keep the timer running. Upon expiration of the timer, if the UE (202) does not have an emergency PDU session, the UE (202) may initiate registration, if the UE (202) is still camped on the selected PLMN. Upon expiration of the timer, if the UE (202) has the emergency PDU session, the UE (202) shall initiate registration after release of the emergency PDU session, if the UE (202) is still camped on the selected PLMN.

[0203] In an embodiment of the disclosure, the UE (202), upon determining that the disaster condition has ended and selecting the PLMN (the third PLMN (208)), shall check if the UE (202) is configured or has the stored value of the disaster return wait range from the third PLMN (208) or not. If the UE (202) is not configured or doesn't have the stored value of the disaster return wait range from the third PLMN (208), then the UE (202) does not generate the random number value within the disaster return wait range. Then the UE (202) does not start the timer with the generated random number value. The UE (202) shall perform registration on the selected PLMN.

[0204] In an embodiment of the disclosure, when the registered PLMN Network or the Home PLMN (HPLMN) (for example, any Network Function or Entity) includes Disaster return wait range in any of the NAS signaling message (for example, Registration Accept, UE CONFIGURATION UPDATE, DEREGISTRATION Request etc.) to the UE (202), the registered PLMN may also include the PLMN-ID or the list of the PLMN-ID(s) for which the Disaster Return Wait Range is applicable. The UE (202) may store, update, or replace the Disaster return wait range for the indicated or included PLMN(s). For example, if UE (202) is storing the Disaster Return Wait range per PLMN. In an embodiment of the disclosure, the UE (202) may store or update the Disaster return wait range value stored in the UE (ME / USIM), in general, for example, not specific to the PLMN. The UE (202) may store the PLMN-ID or the list of PLMN-ID(s), as indicated by the Network, for which the Disaster Return wait range is applicable and apply the Disaster Return Wait Range for the indicated or included PLMN-ID(s) only. The UE (202) shall not apply Disaster Return Wait Range if the selected PLMN after the disaster condition has ended is not same / present in the indicated / included PLMN-ID(s) or the list of PLMN-ID(s).

[0205] In an embodiment of the disclosure, upon determining that the disaster condition has ended and that the UE (202) shall perform PLMN selection as specified in 3GPP TS 23.122, and the UE (202) selecting the PLMN and the UE (202) has the stored the disaster return wait range, the UE (202) shall perform any of the below steps in any order or combinations.

[0206] FIG. 4 shows an example flowchart showing the UE (202) has stored the Disaster Return Wait Range per PLMN or the Network has configured the Disaster Return Wait Range per PLMN, according to an embodiment of the disclosure. At block 402, if the UE (202) has stored the Disaster Return Wait Range per PLMN (or PLMN-ID) (or optionally per PLMN and RAT combination) or if the Network (HPLMN or the Registered PLMN (RPLMN)) has configured the Disaster Return Wait Range per PLMN (or PLMN-ID) (or optionally per PLMN and RAT combination).

[0207] At block 404, if the UE (202) initiates registration for disaster roaming service optionally including the UE Determined PLMN with Disaster Condition IE in any of the AS / NAS signaling message (for example, REGISTRATION REQUEST message), while registering for Disaster roaming services (for example, on the second PLMN (206)). Then at block 406, if the registered PLMN (for example, the PLMN on which UE (202) has registered for the disaster roaming before the disaster condition ended (for example, the second PLMN (206))) had configured / indicated / included Disaster Return Wait range in any of AS / NAS signaling message, then the UE (202) shall generate the random number value within the disaster return wait range and the UE (202) shall start the timer with the generated random number value. While the timer is running, the UE (202) shall not initiate registration on the selected PLMN except if the UE (202) needs to request the emergency PDU session. That is in this case the UE (202) will assume the configured the disaster return wait range is applicable to at least one of all the allowable and forbidden PLMNs. At block 408, if the registered PLMN (for example, the PLMN on which UE (202) has registered for the disaster roaming before the disaster condition ended (for example, the second PLMN (206))) had not configured / indicated / included Disaster Return Wait range in any of AS / NAS signaling message, then the UE (202) shall not generate the random number value within the disaster return wait range. The UE (202) shall not start the timer with the generated random number value. The UE (202) shall perform the registration procedure or any NAS / AS signaling procedure on the selected PLMN. At block 410, if the registered PLMN / Network (for example, the PLMN on which UE (202) has registered for the disaster roaming before the disaster condition ended (for example, the second PLMN (206))) had configured / indicated / included Disaster Return Wait range in any of AS / NAS signaling message and also included the PLMN-ID or the list of PLMN-ID(s) for which the Disaster Return Wait Range is applicable, then if the selected PLMN is same as the PLMN-ID or present in the list of PLMN-ID(s) indicated / included by the Network. The UE (202) shall generate the random number value within the disaster return wait range and the UE (202) shall start the timer with the generated random number value. While the timer is running, the UE (202) shall not initiate registration on the selected PLMN except if the UE needs to request the emergency PDU session. At block 412, if the registered PLMN / Network (for example, the PLMN on which UE (202) has registered for the disaster roaming before the disaster condition ended (for example, the second PLMN (206))) had configured / indicated / included Disaster Return Wait range in any of AS / NAS signaling message and also included the PLMN-ID or the list of PLMN-ID(s) for which the Disaster Return Wait Range is applicable, then if the selected PLMN is different / not same as the PLMN-ID or not present in the list of PLMN-ID(s) indicated / included by the Network, then the UE (202) shall not generate the random number within the disaster return wait range and the UE (202) shall not start the timer with the generated random number value. The UE (202) shall perform the registration procedure or any NAS / AS signaling procedure on the selected PLMN. At block 414, if the registered PLMN (for example, the PLMN on which UE (202) has registered for the disaster roaming before the disaster condition ended (for example, the second PLMN (206))) had configured / indicated / included Disaster Return Wait range in any of AS / NAS signaling message and optionally not included / indicated any PLMN-ID for which the disaster return wait range is applicable, then the UE (202) shall generate the random number value within the disaster return wait range and the UE (202) shall start the timer with the generated random number value when the UE determined PLMN with the disaster condition is selected after the disaster condition has ended. While the timer is running, the UE (202) shall not initiate registration on the selected PLMN except if the UE (202) needs to request the emergency PDU session. That is in this case the UE (202) will assume the configured the disaster return wait range is applicable to the UE determined PLMN with the disaster condition. If the UE (202) selects the PLMN other than UE determined PLMN with the disaster condition the UE (202) shall not generate the random number value within the disaster return wait range and the UE (202) shall not start the timer with the generated random number value.

[0208] At block 416, if the UE Determined PLMN with Disaster Condition IE was not included by the UE (202) in any of the AS / NAS signaling message (for example, REGISTRATION REQUEST message), optionally while registering for Disaster roaming services (for example, on the second PLMN (206)). Then at block 418, if the UE (202) selects any PLMN (optionally any PLMN and RAT combination), then the UE (202) shall generate the random number value within the disaster return wait range and the UE (202) shall start the timer with the generated random number value. While the timer is running, the UE (202) shall not initiate registration on the selected PLMN except if the UE (202) needs to request the emergency PDU session. If condition of block 416 is satisfied then at block 420, if the registered PLMN / Network (for example, the PLMN on which UE (202) has registered for the disaster roaming before the disaster condition ended (for example, the second PLMN (206))) had configured / indicated / included Disaster Return Wait range in any of AS / NAS signaling message and also included the PLMN-ID or the list of PLMN-ID(s) for which the Disaster Return Wait Range is applicable, then if the selected PLMN is same as the PLMN-ID or present in the list of PLMN-ID(s) indicated / included by the Network, then then the UE (202) shall generate the random number value within the disaster return wait range and the UE (202) shall start the timer with the generated random number value. While the timer is running, the UE (202) shall not initiate registration on the selected PLMN except if the UE (202) needs to request the emergency PDU session. If condition of block 416 is satisfied then at block 422, if the registered PLMN / Network (for example, the PLMN on which UE (202) has registered for the disaster roaming before the disaster condition ended (for example, the second PLMN (206))) had configured / indicated / included Disaster Return Wait range in any of AS / NAS signaling message and also included the PLMN-ID or the list of PLMN-ID(s) for which the Disaster Return Wait Range is applicable, then if the selected PLMN is different / not same as the PLMN-ID or not present in the list of PLMN-ID(s) indicated / included by the Network, then the UE (202) shall not generate the random number value within the disaster return wait range and the UE (202) shall not start the timer with the generated random number value. The UE (202) shall perform the registration procedure or any NAS / AS signaling procedure on the selected PLMN. If condition of block 416 is satisfied then at block 424, if the registered PLMN / Network (for example, the PLMN on which UE (202) has registered for the disaster roaming before the disaster condition ended (for example, the second PLMN (206))) had configured / indicated / included the PLMN with the disaster condition (for example, the first PLMN (204)) or the UE determined PLMN with the disaster condition in any IE or in any AS / NAS signaling message, then if the selected PLMN is same as the PLMN with the disaster condition or the UE determined PLMN with the disaster condition indicated / included by the Network, then the UE (202) shall generate the random number value within the disaster return wait range and the UE (202) start the timer with the generated random number value. While the timer is running, the UE (202) shall not initiate registration on the selected PLMN except if the UE (202) needs to request the emergency PDU session. If condition of block 416 is satisfied then at block 426, if the registered PLMN / Network (for example, the PLMN on which UE has registered for the disaster roaming before the disaster condition ended (for example, the second PLMN (206))) had configured / indicated / included the PLMN with the disaster condition (for example, the first PLMN (204)) or the UE determined PLMN with the disaster condition in any IE or in any AS / NAS signaling message, then if the selected PLMN is different / not same as the PLMN with the disaster condition or the UE determined PLMN with the disaster condition indicated / included by the Network, then the UE (202) shall not generate the random number value within the disaster return wait range and the UE (202) shall not start the timer with the generated random number value. The UE (202) shall perform the registration procedure or any NAS / AS signaling procedure on the selected PLMN.

[0209] At block 428, if the UE (202) has stored / updated (in ME / USIM) the Disaster Return Wait Range per PLMN or per PLMN-ID(s), and if there is the stored the disaster return wait range for the selected PLMN, then the UE (202) shall generate the random number value within the disaster return wait range and the UE (202) start the timer with the generated random number value. While the timer is running, the UE (202) shall not initiate registration on the selected PLMN except if the UE needs to request the emergency PDU session.

[0210] At block 430, if the UE (202) has stored / updated (in ME / USIM) the Disaster Return Wait Range per PLMN or per PLMN-ID(s), and if there is no stored the disaster return wait range for the selected PLMN, then the UE (202) shall not generate the random number value within the disaster return wait range and the UE (202) shall not start the timer with the generated random number value. The UE (202) shall perform the registration procedure or any NAS / AS signaling procedure on the selected PLMN.

[0211] At block 432, if the registered PLMN (for example, the PLMN on which UE (202) has registered for the disaster roaming before the disaster condition ended (for example, the second PLMN (206))) had not configured / indicated / included Disaster Return Wait range in any of AS / NAS signaling message, and if the UE 202 has stored Disaster Return Wait Range from some other PLMN (for example, the third PLMN (208)), if the selected PLMN is same as PLMN which has configured the Disaster Return Wait Range (for example, the third PLMN (208)) or if the selected PLMN is same as the PLMN for which the Disaster Return Wait Range has been configured in the UE (202), then the UE (202) shall generate the random number value within the disaster return wait range and the UE (202) start the timer with the generated random number value. While the timer is running, the UE (202) shall not initiate registration on the selected PLMN except if the UE (202) needs to request the emergency PDU session.

[0212] At block 434, if the registered PLMN (for example, the PLMN on which UE (202) has registered for the disaster roaming before the disaster condition ended (for example, the second PLMN (206))) had not configured / indicated / included Disaster Return Wait range in any of AS / NAS signaling message, and if the UE (202) has stored Disaster Return Wait Range from some other PLMN (for example, the third PLMN (208)), if the selected PLMN is different / not same as PLMN which has configured the Disaster Return Wait Range or if the selected PLMN is different / not same as the PLMN for which the Disaster Return Wait Range has been configured in the UE (202), then the UE (202) shall not generate the random number value within the disaster return wait range and the UE (202) shall not start the timer. The UE (202) shall perform the registration procedure or any NAS / AS signaling procedure on the selected PLMN.

[0213] FIG. 5 shows an example flowchart explaining the scenarios, whether the UE (202) or the network has stored the Disaster Return Wait Range not on a per PLMN basis or the UE (202) or the network has stored only one value of Disaster Return Wait Range, according to an embodiment of the disclosure. At block 502, if the UE (202) has stored the Disaster Return Wait Range not on the per PLMN (or PLMN-ID) basis (or optionally per PLMN and RAT combination) (for example, UE (202) has stored only one value of Disaster Return Wait Range) or if the Network (HPLMN or the Registered PLMN (RPLMN)) has not configured the Disaster Return Wait Range on per PLMN (or PLMN-ID) basis (or optionally per PLMN and RAT combination) (for example, Network has configured only one value of Disaster Return Wait Range). Further, at block 504, if the UE Determined PLMN with Disaster Condition IE was included by the UE (202) in any of the AS / NAS signaling message (for example, REGISTRATION REQUEST message), optionally while registering for Disaster roaming services (for example, on the second PLMN (206)), then, at block 506, if the registered PLMN (for example, the PLMN on which the UE (202) has registered for the disaster roaming before the disaster condition ended (for example, the second PLMN (206))) had configured / indicated / included Disaster Return Wait range in any of AS / NAS signaling message, then the UE (202) shall generate the random number value within the disaster return wait range and the UE (202) shall start the timer with the generated random number value. While the timer is running, the UE (202) shall not initiate registration on the selected PLMN except if the UE (202) needs to request the emergency PDU session. At block 508, if the registered PLMN (for example, the PLMN on which the UE (202) has registered for the disaster roaming before the disaster condition ended (for example, the second PLMN (206))) had not configured / indicated / included Disaster Return Wait range in any of AS / NAS signaling message, then the UE (202) shall not generate the random number value within the disaster return wait range and the UE (202) shall not start the timer with the generated random number value. The UE (202) shall perform the registration procedure or any NAS / AS signaling procedure on the selected PLMN. At block 510, if the registered PLMN / Network (for example, the PLMN on which UE (202) has registered for the disaster roaming before the disaster condition ended (for example, the second PLMN (206))) had configured / indicated / included Disaster Return Wait range in any of AS / NAS signaling message and also included the PLMN-ID or the list of PLMN-ID(s) for which the Disaster Return Wait Range is applicable, then if the selected PLMN is same as the PLMN-ID or present in the list of PLMN-ID(s) indicated / included by the Network, then then the UE (202) shall generate the random number value within the disaster return wait range and start the timer with the generated random number value. While the timer is running, the UE (202) shall not initiate registration on the selected PLMN except if the UE (202) needs to request the emergency PDU session. At block 512, if the registered PLMN / Network (for example, the PLMN on which UE (202) has registered for the disaster roaming before the disaster condition ended (for example, the second PLMN (206))) had configured / indicated / included Disaster Return Wait range in any of AS / NAS signaling message and also included the PLMN-ID or the list of PLMN-ID(s) for which the Disaster Return Wait Range is applicable, then if the selected PLMN is different / not same as the PLMN-ID or not present in the list of PLMN-ID(s) indicated / included by the Network, then the UE (202) shall not generate the random number value within the disaster return wait range and the UE (202) shall not start the timer with the generated random number value. The UE (202) shall perform the registration procedure or any NAS / AS signaling procedure on the selected PLMN. At block 514, if the registered PLMN (for example, the PLMN on which the UE (202) has registered for the disaster roaming before the disaster condition ended (for example, the second PLMN (206))) had configured / indicated / included Disaster Return Wait range in any of AS / NAS signaling message and optionally not included / indicated any PLMN-ID for which the disaster return wait range is applicable, then the UE (202) shall generate the random number value within the disaster return wait range and the UE (202) shall start the timer with the generated random number value when the UE determined PLMN with the disaster condition is selected after the disaster condition has ended. While the timer is running, the UE (202) shall not initiate registration on the selected PLMN except if the UE (202) needs to request the emergency PDU session. That is in this case the UE (202) will assume the configured the disaster return wait range is applicable to the UE determined PLMN with the disaster condition. If the UE (202) selects the PLMN other than UE determined PLMN with the disaster condition the UE (202) shall not generate the random number value within the disaster return wait range and the UE (202) shall not start the timer with the generated random number value.

[0214] At block 516, if the UE Determined PLMN with Disaster Condition IE was not included by the UE (202) in any of the AS / NAS signaling message (for example, REGISTRATION REQUEST message), optionally while registering for Disaster roaming services (for example, on the second PLMN (206)), then at block 518, if the UE (202) selects any PLMN (optionally any PLMN and RAT combination), then the UE (202) shall generate the random number value within the disaster return wait range and the UE (202) shall start the timer with the generated random number value. While the timer is running, the UE (202) shall not initiate the registration procedure on the selected PLMN except if the UE (202) needs to request the emergency PDU session. At block 520, if the registered PLMN / Network (for example, the PLMN on which UE (202) has registered for the disaster roaming before the disaster condition ended (for example, the second PLMN (206))) had configured / indicated / included Disaster Return Wait range in any of AS / NAS signaling message and also included the PLMN-ID or the list of PLMN-ID(s) for which the Disaster Return Wait Range is applicable, then if the selected PLMN is same as the PLMN-ID or present in the list of PLMN-ID(s) indicated / included by the Network, then then the UE (202) shall generate the random number value within the disaster return wait range and the UE (202) shall start the timer with the generated random number value. While the timer is running, the UE (202) shall not initiate the registration procedure on the selected PLMN except if the UE (202) needs to request the emergency PDU session. At block 522, if the registered PLMN / Network (for example, the PLMN on which the UE (202) has registered for the disaster roaming before the disaster condition ended (for example, the second PLMN (206))) had configured / indicated / included Disaster Return Wait range in any of AS / NAS signaling message and also included the PLMN-ID or the list of PLMN-ID(s) for which the Disaster Return Wait Range is applicable, then if the selected PLMN is different / not same as the PLMN-ID or not present in the list of PLMN-ID(s) indicated / included by the Network, then the UE (202) shall not generate the random number value within the disaster return wait range and the UE (202) shall not start the timer with the generated random number value. The UE (202) shall perform the registration procedure or any NAS / AS signaling procedure on the selected PLMN. At block 524, if the registered PLMN / Network (for example, the PLMN on which the UE (202) has registered for the disaster roaming before the disaster condition ended (for example, the second PLMN (206))) had configured / indicated / included the PLMN with the disaster condition (for example, the first PLMN (204)) or the UE determined PLMN with the disaster condition in any IE or in any AS / NAS signaling message, then if the selected PLMN is same as the PLMN with the disaster condition or the UE determined PLMN with the disaster condition indicated / included by the Network, then the UE (202) shall generate the random number value within the disaster return wait range and the UE (202) shall start the timer with the generated random number value. While the timer is running, the UE (202) shall not initiate the registration procedure on the selected PLMN except if the UE (202) needs to request the emergency PDU session. At block 526, if the registered PLMN / Network (for example, the PLMN on which UE (202) has registered for the disaster roaming before the disaster condition ended (for example, the second PLMN (206))) had configured / indicated / included the PLMN with the disaster condition (for example, the first PLMN (204)) or the UE determined PLMN with the disaster condition in any IE or in any AS / NAS signaling message, then if the selected PLMN is different / not same as the PLMN with the disaster condition or the UE determined PLMN with the disaster condition indicated / included by the Network, then the UE (202) shall not generate the random number value within the disaster return wait range and the UE (202) shall not start the timer with the generated random number value. The UE (202) shall perform the registration procedure or any NAS / AS signaling procedure on the selected PLMN. At block 528, if the registered PLMN (for example, the PLMN on which UE (202) has registered for the disaster roaming before the disaster condition ended (for example, the second PLMN (206))) had configured / indicated / included Disaster Return Wait range in any of AS / NAS signaling message and optionally not included / indicated any PLMN-ID for which the disaster return wait range is applicable, then the UE (202) shall generate the random number value within the disaster return wait range and the UE (202) shall start the timer with the generated random number value when the UE determined PLMN with the disaster condition is selected after the disaster condition has ended. While the timer is running, the UE (202) shall not initiate the registration procedure on the selected PLMN except if the UE (202) needs to request the emergency PDU session. That is in this case the UE (202) will assume the configured the disaster return wait range is applicable to the UE determined PLMN with the disaster condition. If the UE (202) selects the PLMN other than UE determined PLMN with the disaster condition the UE (202) shall not generate the random number value within the disaster return wait range and the UE (202) shall not start the timer with the generated random number value.

[0215] At block 530, if the UE Determined PLMN with Disaster Condition IE was not included by the UE (202) in any of the AS / NAS signaling message (for example, REGISTRATION REQUEST message), optionally while registering for Disaster roaming services (for example, on the second PLMN (206)) and if the registered PLMN / Network (for example, the PLMN on which the UE (202) has registered for the disaster roaming before the disaster condition ended (for example, the second PLMN (206))) had not configured / indicated / included the PLMN with the disaster condition (for example, the first PLMN (204)) or not included the UE determined PLMN with the disaster condition in any IE or in any AS / NAS signaling message, then for any selected PLMN (or PLMN and RAT combination), the UE (202) shall generate the random number value within the disaster return wait range and the UE (202) start the timer with the generated random number value. While the timer is running, the UE (202) shall not initiate the registration procedure on the selected PLMN except if the UE (202) needs to request the emergency PDU session.

[0216] At block 532, if the registered PLMN (for example, the PLMN on which the UE (202) has registered for the disaster roaming before the disaster condition ended (for example, the second PLMN (206))) had not configured / indicated / included Disaster Return Wait range in any of AS / NAS signaling message, and if the UE (202) has stored Disaster Return Wait Range from some other PLMN (for example, the third PLMN (208)), if the selected PLMN is same as PLMN which has configured the Disaster Return Wait Range (for example, the third PLMN (208)) or if the selected PLMN is same as the PLMN for which the Disaster Return Wait Range has been configured in the UE (202), then the UE (202) shall generate the random number value within the disaster return wait range and the UE shall start the timer with the generated random number value. While the timer is running, the UE (202) shall not initiate the registration procedure on the selected PLMN except if the UE (202) needs to request the emergency PDU session

[0217] At block 534, if the registered PLMN (for example, the PLMN on which the UE (202) has registered for the disaster roaming before the disaster condition ended (for example, the second PLMN (206))) had not configured / indicated / included Disaster Return Wait range in any of AS / NAS signaling message, and if the UE (202) has stored Disaster Return Wait Range from some other PLMN (for example, the third PLMN (208)), if the selected PLMN is different / not same as PLMN which has configured the Disaster Return Wait Range or if the selected PLMN is different / not same as the PLMN for which the Disaster Return Wait Range has been configured in the UE (202), then the UE (202) shall not generate the random number value within the disaster return wait range and the UE (202) shall not start the timer with the generated random number value. The UE (202) shall perform the registration procedure or any NAS / AS signaling procedure on the selected PLMN.

[0218] FIG. 6 shows a flowchart for a method (600) handling a timer in the disaster condition, according to an embodiment of the disclosure. At step 602, the UE (202) may be registered with the first PLMN (204) for normal services. Further, at step 604, the network (for example the first PLMN (204)) may configure the disaster roaming wait range and the disaster return wait range for the UE (202). At step 606, in uncertain situations, the disaster condition occurs at the first PLMN (204), the UE registers with the second PLMN (206) to receive the disaster roaming services. At step 608, when the disaster condition ends, and the UE (202) selects the PLMN, the UE (202) has the stored the disaster return wait range. At step 610, the UE (202) determines whether the disaster return wait range is configured by at least one of the second PLMN (206) providing the disaster roaming services, and the selected PLMN. At step 612, the UE (202) generates the random number value within the disaster return wait range on determining the disaster return wait range is configured by at least one of the second PLMN (206) providing the disaster roaming services, and the selected PLMN. At step 614, the UE (202) starts the timer with the generated random number value. The UE (202) initiates the registration procedure on the selected PLMN, if the timer has expired, or the timer has not started.

[0219] In an embodiment of the disclosure, after the disaster condition has ended, the UE (202) selects the UE determined PLMN with the disaster condition and if UE determined PLMN with the disaster condition had NOT configured the disaster return wait range then the UE (202) shall NOT generate the random number value within the disaster return wait range and shall NOT start the timer with the generated random number value.

[0220] In an embodiment of the disclosure, after the disaster condition has ended, the UE (202) does not select the UE determined PLMN with the disaster condition. If the UE determined PLMN with the disaster condition had configured the disaster return wait range then the UE (202) shall not generate the random number value within the disaster return wait range and shall not start the timer with the generated random number value.

[0221] In an embodiment of the disclosure, after the disaster condition has ended, the UE (202) does not select the UE determined PLMN with the disaster condition. If the UE determined PLMN with the disaster condition had NOT configured the disaster return wait range then the UE (202) shall generate the random number value within the disaster return wait range. The UE (202) shall start the timer with the generated random number value if the UE (202) selects the same PLMN which had actually configured in the UE (202) the disaster return wait range.

[0222] In an embodiment of the disclosure, the PLMN-ID(s) indicated by the registered PLMN which can be forbidden PLMN (for e.g. PLMN providing the disaster roaming service) or the allowable PLMN (which can provide normal services) is at least one of the UE determined PLMN with the disaster condition or any other allowable PLMN or the forbidden PLMN.

[0223] In an embodiment of the disclosure, the selected PLMN is at least one of the UE determined PLMN with the disaster condition or any other allowable PLMN or the forbidden PLMN.

[0224] In an embodiment of the disclosure, the UE determined PLMN with the disaster condition is at least one of the PLMN-ID indicated by the UE to the network in the NAS message e.g. Registration request message as UE determined PLMN with the disaster condition or using the 5G-GUTI, or the PLMN previously with the disaster condition, or network indicated (in the NAS message or by broadcast) PLMN with the disaster condition to the UE.

[0225] The embodiments disclosed herein can be implemented through at least one software program running on at least one hardware device and performing network management functions to control the network elements. The elements include blocks which can be at least one of the hardware device, or the combination of hardware device and software module.

[0226] The various actions in method 600 may be performed in the order presented, in a different order or simultaneously. Further, in some embodiments, some actions listed in FIG. 6 may be omitted.

[0227] According to an embodiment of the disclosure, the method further comprises: in case that the timer is expired or the timer is not started, performing a registration procedure on the selected first PLMN.

[0228] According to an embodiment of the disclosure, the method further comprises: stopping the registration procedure on the selected first PLMN while the timer is running.

[0229] According to an embodiment of the disclosure, the method further comprises: in case that determining that the disaster return wait range is not provided by the first PLMN or the second PLMN, performing a registration procedure on the selected first PLMN.

[0230] According to an embodiment of the disclosure, wherein the disaster return wait range is stored in the UE.

[0231] According to an embodiment of the disclosure, wherein the first PLMN is a PLMN previously with the disaster condition.

[0232] According to an embodiment of the disclosure, the method comprises: performing the registration procedure if the UE is still camped on the selected first PLMN.

[0233] According to an embodiment of the disclosure, the method further comprises: performing a registration procedure for an emergency service on the selected first PLMN while the timer is running; and in case that the timer is expired and an emergency protocol data unit (PDU) session exists, performing the registration procedure after a release of the emergency PDU session.

[0234] According to an embodiment of the disclosure, wherein the at least one processor is further configured to: in case that the timer is expired or the timer is not started, perform a registration procedure on the selected first PLMN.

[0235] According to an embodiment of the disclosure, wherein the at least one processor is further configured to: stop the registration procedure on the selected first PLMN while the timer is running.

[0236] According to an embodiment of the disclosure, wherein the at least one processor is further configured to: in case that determining that the disaster return wait range is not provided by the first PLMN or the second PLMN, perform a registration procedure on the selected first PLMN.

[0237] According to an embodiment of the disclosure, wherein the at least one processor is configured to: perform the registration procedure if the UE is still camped on the selected first PLMN.

[0238] The embodiments disclosed herein describe methods and systems for handling a timer in the disaster conditions in wireless communication. Therefore, it is understood that the scope of the protection is extended to such a program and in addition to a readable computer means having a message therein, such computer readable storage means contain program code means for implementation of one or more steps of the method, when the program runs on a server or mobile device or any suitable programmable device. The method is implemented in at least one embodiment through or together with a software program written in e.g., Very high-speed integrated circuit Hardware Description Language (VHDL) another programming language or implemented by one or more VHDL or several software modules being executed on at least one hardware device. The hardware device can be any kind of portable device that can be programmed. The device may also include means which could be e.g., hardware means like e.g., an ASIC, or a combination of hardware and software means, e.g., an ASIC and an FPGA, or at least one microprocessor and at least one memory with software modules located therein. The method embodiments described herein could be implemented partly in hardware and partly in software. Alternatively, the disclosure may be implemented on different hardware devices, e.g., using a plurality of CPUs.

[0239] The foregoing description of the specific embodiments will so fully reveal the general nature of the embodiments herein that others can, by applying current knowledge, readily modify and / or adapt for various applications such specific embodiments without departing from the generic concept, and, therefore, such adaptations and modifications should and are intended to be comprehended within the meaning and range of equivalents of the disclosed embodiments. It is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation. Therefore, while the embodiments herein have been described in terms of embodiments and examples, those skilled in the art will recognize that the embodiments and examples disclosed herein can be practiced with modification within the scope of the embodiments as described herein.

Claims

1.A method performed by a user equipment (UE) in a wireless communication system, the method comprising:in case that determining that a disaster condition is ended, selecting a first public land mobile network (PLMN);determining whether a disaster return wait range is provided by the selected first PLMN or a second PLMN providing a disaster roaming service;in case that determining that the disaster return wait range is provided by the first PLMN or the second PLMN, generating a random number within the disaster return wait range; andstarting a timer with the generated random number.2.The method of claim 1, further comprising:in case that the timer is expired or the timer is not started, performing a registration procedure on the selected first PLMN.3.The method of claim 2,further comprising:stopping the registration procedure on the selected first PLMN while the timer is running.4.The method of claim 1, further comprising:in case that determining that the disaster return wait range is not provided by the first PLMN or the second PLMN, performing a registration procedure on the selected first PLMN.5.The method of claim 1, wherein the disaster return wait range is stored in the UE.6.The method of claim 1, wherein the first PLMN is a PLMN previously with the disaster condition.7.The method of claim 2, wherein the performing of the registration procedure comprises:performing the registration procedure if the UE is still camped on the selected first PLMN.8.The method of claim 3, further comprising:performing a registration procedure for an emergency service on the selected first PLMN while the timer is running; andin case that the timer is expired and an emergency protocol data unit (PDU) session exists, performing the registration procedure after a release of the emergency PDU session.9.A user equipment (UE) in a wireless communication system, the UE comprising:a transceiver; andat least one processor coupled to the transceiver and configured to:in case that determining that a disaster condition is ended, select a first public land mobile network (PLMN),determine whether a disaster return wait range is provided by the selected first PLMN or a second PLMN providing a disaster roaming service,in case that determining that the disaster return wait range is provided by the first PLMN or the second PLMN, generate a random number within the disaster return wait range,start a timer with the generated random number.10.The UE of claim 9, wherein the at least one processor is further configured to:in case that the timer is expired or the timer is not started, perform a registration procedure on the selected first PLMN.11.The UE of claim 10, wherein the at least one processor is further configured to:stop the registration procedure on the selected first PLMN while the timer is running.12.The UE of claim 9, wherein the at least one processor is further configured to:in case that determining that the disaster return wait range is not provided by the first PLMN or the second PLMN, perform a registration procedure on the selected first PLMN.13.The UE of claim 9, wherein the disaster return wait range is stored in the UE.14.The UE of claim 9, wherein the first PLMN is a PLMN previously with the disaster condition.15.The UE of claim 10, wherein the at least one processor is configured to:perform the registration procedure if the UE is still camped on the selected first PLMN.

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