Access control for a user equipment in a 4g radio access technology disaster roaming scenario

Abstract

A method performed by a user equipment (UE) is provided. The method includes obtaining information that a disaster condition applies to a next generation radio access network (NG-RAN) of a first public land mobile network (PLMN) in which the UE is roaming, wherein the UE is restricted from accessing a first evolved universal mobile telecommunications system (UMTS) terrestrial radio access network (E-UTRAN) of the first PLMN. The method includes sending, to a radio resource control (RRC) layer of the UE based on the information that the disaster condition applies to the NG-RAN, a request to establish or resume a RRC connection toward an E-UTRAN, and an indication that the disaster condition applies to the NG-RAN. The method includes receiving, at the RRC layer from the E-UTRAN, broadcast information that includes barring information for the disaster condition, and performing an access barring check using the barring information.

Description

ACCESS CONTROL FOR A USER EQUIPMENT IN A 4G RADIO ACCESS TECHNOLOGY DISASTER ROAMING SCENARIO TECHNOLOGICAL FIELD

[0001] The present disclosure relates generally to telecommunications and, in particular, to minimization of service interruption (MINT) in a public land mobile network.BACKGROUND

[0002] Telecommunications systems can be seen as facilities that enable communications between two or more entities such as between two user equipment, between a user equipment and a base station, between two base stations, a user equipment and a network function of a communication network and / or a base station and other nodes. A telecommunications system can include a communication network and one or more user equipment. The communication sessions are established for, for example, communication of data for carrying communications such as voice, video, electronic mail (email), text message, multimedia and / or content data and so on. Non-limiting examples of services provided via communication sessions comprise two-way or multi-way calls, data communication or multimedia services and access to a data network system, such as the Internet.

[0003] In a telecommunications system that includes a wireless communication network, at least a part of a communication session between at least two stations occurs over a wireless link. Examples of wireless communication networks comprise public land mobile networks (PLMN), satellite-based communication networks and different wireless local networks, for example wireless local area networks (WLAN). Some wireless communication networks can be divided into cells, and are therefore often referred to as cellular networks.

[0004] A user can access the telecommunications system by means of an appropriate communication device or terminal. A communication device of a user may be referred to as user equipment (UE) or user device. A communication device is provided with an appropriate signal receiving and transmitting apparatus for enabling communications, for example enabling access to a communication network or communications directly with other users. The communication device may access a carrier provided by, for example, a base station of a cell, and transmit and / or receive communications on the carrier.

[0005] Telecommunications systems have evolved through multiple generations, each bringing advancements in speed, capacity, and functionality. The Evolved Packet System (EPS) represents the 4G architecture, which includes Long-Term Evolution (LTE) and LTE-Advanced (LTE-A) as its radio access technologies. The 5G System (5GS) builds upon EPS, introducing 5G New Radio (5G NR) for enhanced mobile broadband, massive machine-type communications, and ultra-reliable low-latency communications. The future 6G System (6GS) is expected to further revolutionize telecommunications with even more advanced capabilities. These systems are interconnected, with 5GS designed to interwork with EPS forseamless service continuity. The 3rd Generation Partnership Project (3GPP) plays a crucial role in developing and maintaining standards for these telecommunications systems, ensuring global interoperability and evolution from Universal Mobile Telecommunications System (UMTS) (3G) through to the ongoing development of 6G technologies.BRIEF SUMMARY

[0006] Example implementations of the present disclosure are directed to minimization of service interruption (MINT) in a public land mobile network. The present disclosure thus includes, without limitation, the following example implementations.

[0007] Some example implementations provide an apparatus comprising: at least one processor; and at least one memory storing instructions of a user equipment (UE), the instructions when executed by the at least one processor causing the apparatus to perform operations, the operations comprising: obtaining information that a disaster condition applies to a next generation radio access network (NG-RAN) of a first public land mobile network (PLMN) in which the UE is roaming, wherein the UE is restricted from accessing a first evolved universal mobile telecommunications system (UMTS) terrestrial radio access network (E-UTRAN) of the first PLMN; sending, to a radio resource control (RRC) layer of the UE based on the information that the disaster condition applies to the NG-RAN, a request to establish or resume a RRC connection toward an E-UTRAN, and an indication that the disaster condition applies, wherein the E-UTRAN is the first E-UTRAN of the first PLMN or a second E-UTRAN of a second PLMN; receiving, at the RRC layer from the E-UTRAN, broadcast information that includes barring information for the disaster condition; and performing, at the RRC layer, an access barring check using the barring information.

[0008] Some example implementations provide a method performed by a user equipment (UE), the method comprising: obtaining information that a disaster condition applies to a next generation radio access network (NG-RAN) of a first public land mobile network (PLMN) in which the UE is roaming, wherein the UE is restricted from accessing a first evolved universal mobile telecommunications system (UMTS) terrestrial radio access network (E-UTRAN) of the first PLMN; sending, to a radio resource control (RRC) layer of the UE based on the information that the disaster condition applies to the NG-RAN, a request to establish or resume a RRC connection toward an E-UTRAN, and an indication that the disaster condition applies to the NG-RAN, wherein the E-UTRAN is the first E-UTRAN of the first PLMN or a second E-UTRAN of a second PLMN; receiving, at the RRC layer from the E-UTRAN, broadcast information that includes barring information for the disaster condition; and performing, at the RRC layer, an access barring check using the barring information.

[0009] These and other features, aspects, and advantages of the present disclosure will be apparent from a reading of the following detailed description together with the accompanying figures, which are briefly described below. The present disclosure includes any combination of two, three, four or more features orelements set forth in this disclosure, regardless of whether such features or elements are expressly combined or otherwise recited in a specific example implementation described herein. The present disclosure is intended to be read holistically such that any separable features or elements of the disclosure, in any of its aspects and example implementations, should be viewed as combinable unless the context of the disclosure clearly dictates otherwise.

[0010] It will therefore be appreciated that this Brief Summary is provided merely for purposes of summarizing some example implementations so as to provide a basic understanding of some aspects of the disclosure. Accordingly, it will be appreciated that the above described example implementations are merely examples and should not be construed to narrow the scope or spirit of the disclosure in any way. Other example implementations, aspects and advantages will become apparent from the following detailed description taken in conjunction with the accompanying figures which illustrate, by way of example, the principles of some described example implementations.BRIEF DESCRIPTION OF THE FIGURE(S)

[0011] Having thus described example implementations of the disclosure in general terms, reference will now be made to the accompanying figures, which are not necessarily drawn to scale, and wherein:

[0012] FIG. 1 illustrates a telecommunications system that includes one or more public land mobile networks (PLMNs) coupled to one or more external data networks, according to some example implementations of the present disclosure;

[0013] FIG. 2 illustrates a PLMN, according to some example implementations;

[0014] FIG. 3 illustrates an overview of a portion of a radio protocol stack architecture, according to some example implementations;

[0015] FIG. 4 is a signaling chart of a procedure according to some example implementations;

[0016] FIGS. 5Aand 5B are flowcharts illustrating various steps in a method performed by a user equipment (UE), according to various example implementations; and

[0017] FIG. 6 illustrates an apparatus according to some example implementations.DETAILED DESCRIPTION

[0018] Some implementations of the present disclosure will now be described more fully hereinafter with reference to the accompanying figures, in which some, but not all implementations of the disclosure are shown. Indeed, various implementations of the disclosure may be embodied in many different forms and should not be construed as limited to the implementations set forth herein; rather, these example implementations are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art. Like reference numerals refer to like elements throughout.

[0019] Unless specified otherwise or clear from context, references to first, second or the like should not be construed to imply a particular order. A feature described as being above another feature (unless specified otherwise or clear from context) may instead be below, and vice versa; and similarly, features described as being to the left of another feature else may instead be to the right, and vice versa. Also, while reference may be made herein to quantitative measures, values, geometric relationships or the like, unless otherwise stated, any one or more if not all of these may be absolute or approximate to account for acceptable variations that may occur, such as those due to engineering tolerances or the like.

[0020] As used herein, unless specified otherwise or clear from context, the "or” of a set of operands is the "inclusive or” and thereby true if and only if one or more of the operands is true, as opposed to the "exclusive or” which is false when all of the operands are true. Thus, for example, "[A] or [B]” is true if [A] is true, or if [B] is true, or if both [A] and [B] are true. Further, the articles "a” and "an” mean "one or more,” unless specified otherwise or clear from context to be directed to a singular form. Furthermore, it should be understood that unless otherwise specified, the terms "data,” "content,” "digital content,” "information,” and similar terms may be at times used interchangeably. The term "network” may refer to a group of interconnected computers including clients and servers; and within a network, these computers may be interconnected directly or indirectly by various means including via one or more switches, routers, gateways, access points or the like.

[0021] The present disclosure discusses telecommunication systems and mobile or cellular networks and user equipment thereof, and while specific terms may be used, are broadly applicable across various technologies. For instance, while the present disclosure may reference radio access technologies such as 5G NR and 5G Advanced, the present disclosure is equally relevant to next generation radio access technologies, such as 6G. Example implementations of the present disclosure described herein also mention public land mobile networks (PLMNs) and mobile network operators (MNOs), but example implementations are similarly applicable to standalone non-public networks (SNPNs) . Furthermore, although some examples and figures focus on radio access networks (RANs) and in particular radio access networks that operate in accordance with the 3GPP standard for 5G NR (generally referred to as 3GPP access or 3GPP access networks), example implementations are applicable to any type of access networks. This includes not only 3GPP access networks but also non-3GPP access networks, such as wireline access, untrusted non-3GPP access network, and trusted non-3GPP access network using wireless access gateway function (W-AGF), non-3GPP interworking function (N3IWF), or trusted non-3GPP gateway function (TNGF) to connect to a core network (e.g., a 5G core network (5GC) or a 6G core network (6GC)) of a mobile or cellular network.

[0022] Further, as used in this application, the term "circuitry” may refer to one or more or all of the following: (a) hardware-only circuit implementations (such as implementations in only analog and / or digital circuitry); (b) combinations of hardware circuits and software, such as (as applicable): (i) a combination ofanalog and / or digital hardware circuit(s) with software / firmware and (ii) any portions of hardware processor(s) with software (including digital signal processor(s)), software, and memory(ies) that work together to cause an apparatus, such as a mobile phone or server, to perform various functions); or (c) hardware circuit(s) and / or processor(s), such as a microprocessor(s) or a portion of a microprocessor(s), that requires software (e.g., firmware) for operation, but the software may not be present when it is not needed for operation.

[0023] The above definition of circuitry applies to all uses of this term in this application, including in any claims. As a further example, as used in this application, the term circuitry also covers an implementation of merely a hardware circuit or processor (or multiple processors) or portion of a hardware circuit or processor and its (or their) accompanying software and / or firmware. The term circuitry also covers, for example and if applicable to the particular claim element, a baseband integrated circuit or processor integrated circuit for a mobile device or a similar integrated circuit in server, a cellular network device, or other computing or network device.

[0024] FIG. 1 illustrates a telecommunications system 100 according to various example implementations of the present disclosure. Examples of suitable telecommunications systems include UMTS, EPS and 5GS, as well as the future 6GS. The telecommunications system 100 (otherwise referred to as system 100) generally includes one or more mobile or cellular networks, and these mobile or cellular networks may interwork between telecommunications systems. As shown, for example, the system 100 includes one or more PLMNs 102 coupled to one or more other external data networks 104 - notably including a wide area network (WAN) such as the Internet. As will be appreciated, a PLMN may be a standalone PLMN that includes a 5GC, or may be a non-standalone PLMN that includes both an Evolved Packet Core (EPC) and a 5GC connected to a RAN.

[0025] Each of the PLMNs 102 includes a core network (CN) 106, such as the EPC, the 5GC, or a 6GC; and each CN is coupled to one or more RANs 108 that implement one or more radio access technologies (RATs). Examples of these RANs include the evolved UMTS terrestrial radio access network (E-UTRAN) of 4G LTE, the next generation (NG) radio access network (NG-RAN) of 5G NR, and the 6G RAN. As used herein, a "network device” refers to any suitable device of a RAN or a core network of a telecommunications system. Examples of suitable network devices are described in greater detail below.

[0026] Examples of RATs include 3GPP radio access technologies such as GSM, CDMA2000 1xEV-DO (HRPD), CDMA2000 1x (1xRTT), UTRA, E-UTRA, 5G NR, 5G Advanced, and 6G. Other examples of RATs include IEEE 802 technologies such as IEEE 802.11 (Wi-Fi), IEEE 802.15 (including 802.15.1 (WPAN / Bluetooth), 802.15.4 (Zigbee) and 802.15.6 (WBAN)), Bluetooth, Bluetooth Low Energy (BLE), ultra wideband (UWB), and the like. Generally, a RAT may refer to any 2G, 3G, 4G, 5G, 6G or higher generation RAT and their different versions, as well as to any other RAT that may be arranged to interwork with such a RAT to provide access to the CN 106 of a MNO.

[0027] The telecommunications system 100 also includes one or more communication devices that may be varyingly known as user equipment (UE) 110, terminal device, terminal equipment, mobile station or the like. The UE is generally a device configured to communicate with a network device (e.g., an access node such as a RAN node of RAN 108) or a or a further UE in the telecommunications system. The UE may be a portable computer (e.g., laptop, notebook, tablet computer), mobile phone (e.g., cell phone, smartphone), wearable computer (e.g., smartwatch), or the like. In other examples, the UE may be an Internet of things (loT) device, an industrial loT (I loT device), a vehicle equipped with a vehicle-to-everything (V2X) communication technology, or the like. In some examples, as referenced by 3GPP, the UE 110 may be a narrowband loT (NB-loT) device, an enhanced machine-type communication (eMTC) device, a reduced capability (RedCap) device, an ambient loT device, or the like.

[0028] In operation, these UEs 110 may connect to one or more RAN nodes of the RANs 108 according to their particular RATs to thereby access a particular CN 106 of a PLMN 102, or to access one or more of the external data networks 104 (e.g., the Internet) or services provided by the PLMN. The external data network may provide Internet access, or 3rd party services. For example, the International Telecommunication Union (ITU) has classified 5G mobile network services (e.g., services provided by a 5G mobile network) into three categories: enhanced mobile broadband (eMBB), ultra-reliable and low-latency communications (URLLC), and massive machine type communications (mMTC) or massive internet of things (MIoT).

[0029] In various examples, a RAN 108 may be configured to provide one or more macrocells, microcells, picocells, femtocells or the like. The RAN 108 may generally include one or more RAN nodes that interact with UEs 110. In various examples, a RAN node may be referred to as a base station (BS), access point (AP), base transceiver station (BTS). Examples of RAN nodes includes a Node B (NB), evolved NB (eNB), macro BS, NB (MNB) or eNB (MeNB), home BS, NB (HNB) or eNB (HeNB), next generation NB (gNB), enhanced gNB (en-gNB), next generation eNB (ng-eNB), 6G NB (6gNB), or the like. The term 'gNB' in 5G NR may correspond to the eNB in 4G LTE. Also, a NG-RAN node may refer to a gNB or a ng-eNB. And unless otherwise specified, a gNB in 5G NR or a 6gNB in 6G may at times be more generally referred to as a (6)gNB or more simply a gNB.

[0030] The RAN 108 may include some type of network controlling / governing entity responsible for control of the RAN nodes. The network controlling / governing entity and RAN node may be separate or integrated into a single apparatus. The network controlling / governing entity may include processing circuity configured to carry out various management functions for controlling RAN nodes of the RAN 108. The processing circuity may be associated with a memory, computer-readable storage medium or a data storage device comprising a database for maintaining information required in the various management functions.

[0031] FIG. 2 illustrates an example of a PLMN 102, such as 4G LTE, 5G NR or 6G PLMN that communicates with a UE 110 and an external data network 104 of the telecommunications system 100. Asshown, the RAN 108 (e.g., E-UTRAN, NG-RAN, 6G RAN) includes one or more RAN nodes 202 configured to connect one or more UEs to the RAN to thereby access the CN 106 (e.g., EPC, 5GC, 6GC). In 4G LTE, the UE, E-UTRAN and EPC compose EPS. Similarly, in 5G NR, the UE, NG-RAN and 5GC compose the 5GS. And in 6G, the UE, 6G RAN and 6GC compose the 6GS.

[0032] FIG. 3 illustrates an overview of a portion of a radio protocol stack 300 architecture, between a UE 110 and a RAN node 202, according to some example implementations. As shown, the radio protocol stack has two different stacks depending on the type of data that is processed by the stack. User data goes through a user plane (UP) stack 302, signaling messages go through a control plane (CP) stack 304. Both UP and CP stacks are made up of a common structure including a Layer 1 (L1) with a physical layer (PHY) 306, and a layer 2 (L2) with sublayers including medium access control (MAC) 308, radio link control (RLC) 310, and packet data convergence protocol (PDCP) 312. A layer 3 (L3) sits on topof PHY / MAC / RLC / PDCP, and includes sublayers that are different between the CP and UP. In the UP, L3 includes a sublayer referred to as service data adaptation protocol (SDAP) 314 that may be connected to the user plane function (UPF) or other suitable NF in the CN 106. In the CP, L3 includes two sublayers referred to as radio resource control (RRC) 316 and non-access stratum (NAS) 318, and the NAS layer connects to the mobility management network function (MM NF) in the CN.

[0033] Generally, each layer of the 5G radio protocol stack 300 performs a specific data communications task, a service to and for the layer that precedes it. For example, the RRC 316 is part of the access stratum (AS), and acts as a transport layer for NAS messages, which may be encapsulated within RRC signaling. The NAS layer 318 relies on the RRC layer for establishing and maintaining signaling connections with the RAN 108.

[0034] The process of layers of the radio protocol stack 300 performing specific data communication tasks can be likened to placing a letter in a series of envelopes before it is sent through the postal system. Each succeeding envelope adds another layer of processing or overhead information necessary to process the transaction. Together, all the envelopes help make sure the letter gets to the right address and that the message received is identical to the message sent. Once the entire package is received at its destination, the envelopes are opened one by one until the letter itself emerges exactly as written.

[0035] A data flow between a source and destination, such as the UE 110 and RAN node 202, is from top to bottom in the source, across the communications line, and then from bottom to top in the destination. Each time, user data passes downward from one layer to the next layer in the source more processing information is added. When that information is removed and processed by the peer layer in the destination, it causes various tasks (error correction, flow control, etc.) to be performed.

[0036] The UE 110 and the RAN 108 may support minimization of service interruption (MINT) which aims to enable a UE to determine a disaster condition applies to a PLMN 102 (at times referred to as a PLMN-D, the PLMN at which the disaster condition applies), and obtain service from another PLMN offering disasterroaming services. As specified in 3GPP Release 17, upon selecting a PLMN for disaster roaming, if the UE does not have a stored disaster roaming wait range, the UE may perform a registration procedure for disaster roaming services on the selected PLMN.

[0037] If the UE 110 otherwise has a stored disaster roaming wait range, the UE may generate a random number within the disaster roaming wait range and start a timer with the generated random number. While the timer is running, the UE may not initiate registration on the selected PLMN 102 except if the UE needs to request an emergency protocol data unit (PDU) session. Upon expiration of the timer, if the UE does not have an emergency PDU session, the UE may perform a registration procedure for disaster roaming services on the selected PLMN.

[0038] Work has started on a phase 2 of MINT (MINT_Ph2) for 3GPP Release 19. Mint phase 1 (in 3GPP Release 17) includes support for disaster handling with one 5G PLMN to another 5G PLMN. ForMl NT_Ph2, it is desirable that the same VPLMN provide 4GS to the UE when / where the disaster condition applies. For Ml NT_Ph2, subject to regulatory requirements, operator's policy or UE capabilities, the 3GPP system may support a UE 110, with 5G-only national roaming access to a visited PLMN (VPLMN), to obtain 4G connectivity service (e.g., voice call, mobile data service) from that VPLMN in the area where a disaster condition applies. MINT_Ph2 may therefore include support for a 5G RAT (5G NR) of a PLMN to a 4G RAT (4G LTE) of the same PLMN 102 or a 4G RAT of a different PLMN providing disaster service in 4G. In this regard, the 5G RAT and 4G RAT may be provided by respectively an NG-RAN and E-UTRAN of the PLMN.

[0039] In the above scenario, a UE 110 may maintain service from the IP multimedia subsystem (IMS) in the UE's home PLMN (HPLMN) and only connectivity from the VPLMN. The EPS in the VPLMN may support the disaster roaming service, and a 5G-only national roaming UE may be allowed to register for the disaster roaming service in the EPS. In a network deployment with 5G-only national roaming UEs, an operator may configure the 5GS and EPS with different PLMN identifiers (IDs) or use RAT restrictions, etc., to ensure that the 5G-only national roaming UEs cannot access 4G in normal service conditions. But when the NG-RAN is in a disaster condition, 5G-only national roaming UEs may select the E-UTRAN of the same PLMN or a E-UTRAN of a different PLMN that provides disaster services in 4G / EPS.

[0040] One of the key issues in in this mechanism is the prevention of signaling overload in the VPLMN providing the disaster roaming service in EPS, i.e., to avoid an overload condition (e.g., signaling storm) when multiple UEs 110 try at the same time to connect to EPS (4G) when a condition applies in the 5GS of the VPLMN.

[0041] Similar to the disaster roaming wait range described above, an agreement has been made to define a disaster wait range in MINT_Ph2. Once a disaster condition occurs in the VPLMN providing 5G-only national roaming, the UEs 110 currently connected to the VPLMN may migrate to the VPLMN providing disaster roaming services in EPS (since the EPS may be the one that is currently available). The VPLMN providing disaster service in EPS may be the same VPLMN or a different VPLMN. In order to avoidcongestion due to a potential large number of UEs migrating at the same time or within a short period of time to the VPLMN providing disaster roaming services in EPS, the migration of the subscribers / UEs may be made in a distributed and staggered way.

[0042] When the UE 110 sends support for MINT_Ph2 in a registration request message, the access and mobility management function (AMF) in the HPLMN or the registered VPLMN (e.g., the VPLMN providing 5G-only national roaming access) may, in a registration accept message, send a disaster roaming wait range . The UE may only then be allowed to perform a registration attempt to the VPLMN providing disaster roaming services in EPS upon expiration of the disaster roaming wait range timer and once the UE has received indication or understands that the VPLMN providing 5G-only national roaming is under disaster condition.

[0043] Apart from the wait range technique, an access control mechanism is unified access control (UAC) defined in Release 17 MINT for 5G: When a disaster condition applies, an inbound disaster roamer UE 110 supporting Release 17 MINT may activate an access identity 3 (AI3) (i.e., an access identity configured in a UE for which a disaster condition applies). And when the UE wants to make an access attempt, the NAS layer 318 of the UE may provide the AS layer of the UE with AI3. The RAN 108 of the PLMN 102 accepting inbound disaster roamer UEs may broadcast a barring factor for AI3 (uac-BarringFactorForAI3), which governs the rate of access attempts made by inbound disaster roamers. In this way, the RAN may manage / control access attempts from inbound disaster roamer UEs.

[0044] For Ml NT_Ph2, a disaster wait range for EPS may solve the issue of overload condition upto some extent. But the disaster wait range is not enough as the disaster wait range does not dynamically reflect the situation, and the disaster wait range is preconfigured before the disaster condition applies. Access control, similar to UAC, is not defined in EPS as in 5GS, and EPS does not support access identities like AI3 as in 5GS. To be more specific, access control in EPS does not have a parameter which reflect the category of a UE (i.e., access identity). In EPS, each access attempt is characterized by a single parameter "call type” in general whereas in 5GS, each access attempt is characterized by two parameters "access category” and "access identity”: the access category is determined for each access attempt similar to call type and the access identity reflects semi-static status of the UE. EPS therefore cannot stop, regulate or otherwise control inbound disaster roamer UEs 110 to avoid a signaling storm or other overload condition when multiple UEs 110 try at the same time to connect to EPS (4G) when a condition applies in the 5GS of the VPLMN.

[0045] In view of the foregoing, example implementations of the present disclosure provide an access control mechanism in EPS / E-UTRAN in a disaster condition. The access control mechanism of example implementations may control access attempts made by inbound disaster roamer UEs 110 to the E-UTRAN (RAN 108) of a PLMN 102 accepting the disaster roamer UEs. Example implementations are described primarily in the context of a NG-RAN and a E-UTRAN of a (V)PLMN 102. It should be understood, however,that example implementations may equally apply to any of a number of different access networks, including generally a first access network (providing a first RAT) and a second access network (providing a second RAT) of the same or a different (V)PLMN.

[0046] According to some example implementations, a UE 110 may be allowed for 5G-only national roaming in a (V)PLMN 102, and restricted to only 5GS / NG-RAN in the (V)PLMN, such as due to operator configuration or congestion. The UE may be restricted from accessing RANs providing other RATs, including EPS / E-UTRAN.

[0047] The UE 110 may obtain information that a disaster condition applies to the 5GS / NG-RAN of the (V)PLMN, i.e., a PLMN-D in which the disaster condition applies. In some examples, the UE may be informed by the EPS / E-UTRAN that the 5GS / NG-RAN is no longer available, and that the EPS / E-UTRAN is to be used. In a more specific example, an E-UTRAN of a PLMN offering disaster roaming service may broadcast information from which the UE may determine that the NG-RAN of PLMN-D is in a disaster condition. The UE is a 5G-only national roaming UE for the PLMN-D in this implementation. In this regard, the UE is not allowed to register to PLMN-D via any other RATs than 5G NR, and the UE has a forbidden PLMN / access technology list that includes the PLMN-D and 4G RAT (4G LTE) combination or any other PLMN (referred to as PLMN-A) and 4G RAT combination. The UE is allowed to camp on the 4G RAT of the PLMN-A (which may be PLMN-D) and register in case of a disaster condition.

[0048] The access control mechanism of example implementations may be implemented by the E-UTRAN of PLMN-A to allow randomly-delayed connection attempts by a 5G-only roamer UE 110. In some examples, the UE may select the E-UTRAN of PLMN-A based on the information that the disaster condition applies to the NG-RAN. In this regard, the UE may determine a need to request access to the E-UTRAN (second access network) via which the UE is attaching or attached to PLMN-A for disaster roaming when a disaster condition applies to a NG-RAN (first access network) of PLMN-A.

[0049] In some example implementations, the NAS layer 318 of the UE 110 may obtain the information that the disaster condition applies to the NG-RAN of PLMN-D. An EPS mobility management (EMM) (sub)layer of the NAS layer may generate an EMM message for a disaster roaming service, and send a request to the RRC layer 326 establish or resume a RRC connection toward the E-UTRAN of PLMN-A to send the EMM message. The request may include the EMM message and an indication that the disaster condition applies to the NG-RAN. In some examples, the indication that the disaster condition applies may be provided by a call type set to a value indicating that that the disaster condition applies. In other examples, the indication that the disaster condition applies may be provided by an indication which is sent to the RRC layer in addition to a call type.

[0050] The UE 110 (RRC layer 326) may receive, from a cell of the E-UTRAN of PLMN-A, broadcast information that includes barring information for the disaster condition, and perform an access barring check using the barring information. In some examples, the barring information may include a barringfactor. The UE may generate a random number, and compare the barring factor to the random number to determine whether an access attempt to the E-UTRAN of PLMN-A is barred or not barred. In some examples, the access attempt may be barred when the random number is greater than or equal to the barring factor, and the access attempt may not be barred when the random number is less than the barring factor. In other examples, the access attempt may not be barred when the random number is greater than or equal to the barring factor, and the access attempt may be barred when the random number is less than the barring factor.

[0051] In some examples in which the access barring check indicates an access attempt to the cell of the E-UTRAN of PLMN-A is not barred, the UE 110 (RRC layer 326) may send an RRC message to the cell of the E-UTRAN of PLMN-A to establish or resume the RRC connection. The EMM message may then be sent to the E-UTRAN of PLMN-A over the RRC connection. In some other examples in which the access barring check indicates an access attempt to the cell of the E-UTRAN of PLMN-A is barred, the RRC layer may send information to the EMM layer (NAS layer 318) that indicates the access attempt to the cell is barred.

[0052] To further illustrate some example implementations, FIG. 4 is a signaling chart 400 of a procedure according to some example implementations. As shown, the procedure involves a UE 110 (a 5G-only roamer UE) that is in a specific location and connected to a 5G PLMN 102 via a source NG-RAN 108A. The UE may receive information that a disaster condition applies to the source NG-RAN. The UE may at step 401 lose its connection with the source NG-RAN due to the disaster condition.

[0053] The UE 110 may at step 402 determine a need to send an EMM message to a target E-UTRAN 108B for disaster roaming. In this regard, the EMM layer (NAS layer 318) of the UE may generate an EMM message for a disaster roaming service, and determine the need to send the EMM message to the target E-UTRAN. Examples of a suitable EMM message include an attach request, a tracking area update request, a detach request, a service request, an extended service request, a CP service request, or the like.

[0054] In order to send the EMM message, the EMM layer (NAS layer 318) of the UE 110 may request the establishment / resuming of a NAS-signaling connection to the AS layer in the UE. In this regard, the EMM layer may send a request to the RRC layer 326 to establish / resume a RRC connection toward the target E-UTRAN 108B. For the purpose of access control, the EMM layer may also include an indication that the disaster condition applies to the source NG-RAN 108A. In some examples, the indication may be provided by a call type set to a value indicating that that the disaster condition applies (a call type for disaster roaming).

[0055] Upon receiving the request to establish / resume the RRC connection (a NAS signaling connection from the perspective of the EMM layer), the RRC layer 326 layer may at step 403 initiate an access baring check. The RRC layer may at step 404 receive broadcast information from the target E-UTRAN, and thebroadcast information may include barring information such as a barring factor. The RRC layer may draw or otherwise generate a random number rand, which may be uniformly distributed in the range: 0 < rand < 1. The RRC layer may then compare the barring factor to the random number to determine whether an access attempt to the target E-UTRAN 108B is barred or not barred. In some examples, if rand is lower than the value indicated by the barring factor, an access attempt may not be barred; otherwise, an access attempt is barred.

[0056] As shown at step 405, when the access attempt is not barred, the RRC layer 326 may send an RRC message to the target E-UTRAN 108B to establish / resume a RRC connection over which the EMM message may be sent to the target E-UTRAN. When the access attempt is barred, the RRC layer may send information to the EMM layer that indicates an access attempt is barred.

[0057] FIGS. 5Aand 5B are flowcharts illustrating various steps in a method 500 performed by a user equipment (UE), according to various example implementations. The method includes obtaining information that a disaster condition applies to a next generation radio access network (NG-RAN) of a first public land mobile network (PLMN) in which the UE is roaming, wherein the UE is restricted from accessing a first evolved universal mobile telecommunications system (UMTS) terrestrial radio access network (E-UTRAN) of the first PLMN, as shown at block 502 of FIG. 5A. The method includes sending, to a radio resource control (RRC) layer of the UE based on the information that the disaster condition applies to the NG-RAN, a request to establish or resume a RRC connection toward an E-UTRAN, and an indication that the disaster condition applies to the NG-RAN, wherein the E-UTRAN is the first E-UTRAN of the first PLMN or a second E-UTRAN of a second PLMN, as shown at block 504. The method includes receiving, at the RRC layer from the E-UTRAN, broadcast information that includes barring information for the disaster condition, as shown at block 506. And the method includes performing, at the RRC layer, an access barring check using the barring information, as shown at block 508.

[0058] In some examples, the method 500 further includes selecting, based on the information that the disaster condition applies to the NG-RAN, the first E-UTRAN or the second E-UTRAN as the E-UTRAN for the request to establish or resume the RRC connection.

[0059] In some examples, the indication that the disaster condition applies comprises a call type set to a value indicating that that the disaster condition applies.

[0060] In some examples, the indication that the disaster condition applies comprises an indication which is sent to the RRC layer in addition to a call type.

[0061] In some examples, the barring information includes a barring factor, and performing the access barring check at block 508 includes generating a random number, as shown at block 510 of FIG. 5B. In some of these examples, performing the access barring check also includes comparing the barring factor to the random number to determine whether an access attempt to the E-UTRAN is barred or not barred, as shown at block 512.

[0062] In some examples, the access attempt is barred when the random number is greater than or equal to the barring factor, and the access attempt is not barred when the random number is less than the barring factor.

[0063] In some examples, the access barring check indicates an access attempt is not barred, and the method further includes sending an RRC message to the E-UTRAN to establish or resume the RRC connection.

[0064] In some examples, the method 500 further includes generating an evolved packet system (EPS) mobility management (EMM) message for a disaster roaming service. In some of these examples, the request to establish or resume a RRC connection toward the E-UTRAN comprises the EMM message for the RRC layer to send the EMM message over the RRC connection.

[0065] In some examples, the request is sent to the RRC layer at block 504 from an evolved packet system (EPS) mobility management (EMM) layer of the UE. In some of these examples, the access barring check indicates an access attempt is barred, and the method 500 further includes sending, from the RRC layer to the EMM layer, information that indicates the access attempt is barred.

[0066] According to example implementations of the present disclosure, a telecommunications system 100 or PLMN 102, and its components such as a UE 110, CN 106, RAN 108, and / or RAN node 202, may be implemented by various means. Means for implementing the system and its components may include hardware, firmware, software, or combinations thereof. In some examples, one or more apparatuses may be configured to function as or otherwise implement the system and its components shown and described herein. In examples involving more than one apparatus, the respective apparatuses may be connected to or otherwise in communication with one another in a number of different manners, such as directly or indirectly via a wired or wireless network or the like.

[0067] According to some example implementations, at least some of the method 500 described with respect to FIGS. 5A and 5B may be carried out by an apparatus comprising means for performing functions corresponding steps of the method. Examples of a suitable apparatus may include a user equipment, user device, user terminal or the like.

[0068] FIG. 6 illustrates an apparatus 600 in which means for performing various operations includes hardware, alone or under direction of one or more computer programs from a computer-readable storage medium or other memory, such as computer memory, according to some example implementations of the present disclosure. The apparatus may include one or more of each of a number of components such as, for example, processing circuitry 602 connected to computer-readable storage medium or other memory 604.

[0069] The processing circuitry 602 may be composed of one or more processors alone or in combination with one or more computer-readable storage media. The processing circuitry is generally any piece of computer hardware that is capable of processing information such as, for example, data, computerprograms, computer code and / or other suitable electronic information. The processing circuitry is composed of a collection of electronic circuits some of which may be packaged as an integrated circuit or multiple interconnected integrated circuits (an integrated circuit at times more commonly referred to as a "chip”). The processing circuitry may be configured to execute computer programs, which may be stored onboard the processing circuitry or otherwise stored in the memory 604 (of the same or another apparatus).

[0070] The processing circuitry 602 may comprise a number of processors, a multi-core processor or some other type of processor, such as a central processing unit, a graphics processing unit, a tensor processing, unit, or an accelerator, depending on the particular implementation. Further, the processing circuitry may be implemented using a number of heterogeneous processor systems in which a main processor is present with one or more secondary processors on a single chip. As another illustrative example, the processing circuitry may be a symmetric multi-processor system containing multiple processors of the same type. In yet another example, the processing circuitry may be embodied as or otherwise include one or more application specific integrated circuits (ASICs), field programmable gate arrays (FPGAs) or the like. Thus, although the processing circuitry may be capable of executing a computer program to perform one or more functions, the processing circuitry of various examples may be capable of performing one or more functions without the aid of a computer program. In either instance, the processing circuitry may be appropriately programmed to perform functions or operations according to example implementations of the present disclosure.

[0071] The memory 604 is generally any piece of computer hardware that is capable of storing information such as, for example, data, computer programs, instructions 606 (e.g., computer-readable program code) and / or other suitable information either on a temporary basis and / or a permanent basis. The memory may include volatile and / or non-volatile memory, and may be fixed or removable. Examples of suitable memory include recording media, random access memory (RAM), read-only memory (ROM), a hard drive, a flash memory, a thumb drive, a removable computer diskette, an optical disk or some combination thereof.

[0072] The memory 604 is a non-transitory device capable of storing information. One example of a suitable memory is a computer-readable storage medium, which is distinguishable from a computer-readable transmission medium capable of carrying information from one location to another. Examples of suitable computer-readable transmission media comprise electronic carrier signals, telecommunications signals, or some combination thereof. As used herein, the term "non-transitory” is a limitation of the medium itself (i.e., tangible, not a signal) as opposed to a limitation on data storage persistency (e.g., RAM versus ROM). A computer-readable medium as described herein generally refers to a computer-readable storage medium or computer-readable transmission medium. A computer-readable medium is any entity or device capable in which information, such as one or more computer programs or portions thereof, may be stored and carried.

[0073] In addition to the memory 604 (e.g., computer-readable storage medium), the processing circuitry 602 may also be connected to one or more interfaces for displaying, transmitting and / or receiving information. The interfaces may include a communications interface 608 and / or one or more user interfaces. The communications interface may be configured to transmit and / or receive information, such as to and / or from other apparatus(es), network(s) or the like. The communications interface may be configured to transmit and / or receive information by physical (wired) and / or wireless communications links. Examples of suitable communication interfaces include a network interface controller (NIC), wireless NIC (WNIC) or the like.

[0074] The user interfaces may include a display 610 and / or one or more user input interfaces 612. The display may be configured to present or otherwise display information to a user, suitable examples of which include a liquid crystal display (LCD), light-emitting diode (LED) display, organic LED (OLED) display, active-matrix OLED (AMOLED) or the like. The user input interfaces may be wired or wireless, and may be configured to receive information from a user into the apparatus, such as for processing, storage and / or display. Suitable examples of user input interfaces include a microphone, image or video capture device, keyboard or keypad, joystick, touch-sensitive surface (separate from or integrated into a touchscreen), biometric sensor or the like. The user interfaces may further include one or more interfaces for communicating with peripherals such as printers, scanners or the like.

[0075] Execution of the instructions 606 by the processing circuitry 602, or storage of the instructions in the memory 604, supports combinations of operations for implementing example implementations of the present disclosure. In this manner, an apparatus 600 may comprise at least one processing circuitry and at least one memory coupled to the at least one processing circuitry, where the at least one processing circuitry is configured to execute instructions stored in the at least one memory. It will also be understood that one or more functions, and combinations of functions, may be implemented by special purpose hardware-based computer systems and / or processing circuitry which perform the specified functions, or combinations of special purpose hardware and program code instructions.

[0076] Some example implementations of the present disclosure may also be carried out in the form of a computer process defined by one or more computer programs or portions thereof. Example implementations of the present disclosure may be carried out by executing at least one portion of a computer program comprising instructions. The computer program may be in source code form, object code form, or in some intermediate form. The computer program may be stored in a computer-readable medium that is readable by a computer, processing circuitry or other suitable apparatus. As indicated above, for example, the computer program may be stored in a memory, such as a computer-readable storage medium. Additionally or alternatively, for example, the computer program may be stored in a computer-readable transmission medium. The coding of software for carrying out example implementations of the present disclosure is well within the scope of a person of ordinary skill in the art.

[0077] As will be appreciated, any suitable instructions may be loaded onto a computer, a processing circuitry or other programmable apparatus from a memory or a computer-readable medium (e.g., computer-readable storage medium, computer-readable transmission medium) to produce a particular machine, such that the particular machine becomes a means for implementing the functions specified herein. The instructions may also be stored in a computer-readable medium that can direct a computer, a processing circuitry or other programmable apparatus to function in a particular manner to thereby generate a particular machine or particular article of manufacture. In some examples, the instructions stored in the computer-readable medium may produce an article of manufacture, where the article of manufacture becomes a means for implementing functions described herein. The instructions may be retrieved from a computer-readable medium and loaded into a computer, processing circuitry or other programmable apparatus to configure the computer, processing circuitry or other programmable apparatus to execute operations to be performed on or by the computer, processing circuitry or other programmable apparatus.

[0078] Retrieval, loading and execution of instructions comprising program code instructions may be performed sequentially such that one instruction is retrieved, loaded and executed at a time. In some example implementations, retrieval, loading and / or execution may be performed in parallel such that multiple instructions are retrieved, loaded, and / or executed together. Execution of the program code instructions may produce a computer-implemented process such that the instructions executed by the computer, processing circuitry or other programmable apparatus provide operations for implementing functions described herein.

[0079] As explained above and reiterated below, the present disclosure includes, without limitation, the following example implementations.

[0080] Many modifications and other implementations of the disclosure set forth herein will come to mind to one skilled in the art to which the disclosure pertains having the benefit of the teachings presented in the foregoing description and the associated figures. Therefore, it is to be understood that the disclosure is not to be limited to the specific implementations disclosed and that modifications and other implementations are intended to be included within the scope of the appended claims. Moreover, although the foregoing description and the associated figures describe example implementations in the context of certain example combinations of elements and / or functions, it should be appreciated that different combinations of elements and / or functions may be provided by alternative implementations without departing from the scope of the appended claims. In this regard, for example, different combinations of elements and / or functions than those explicitly described above are also contemplated as may be set forth in some of the appended claims. Although specific terms are employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation.

Claims

WE CLAIM:

1. A user equipment (UE) comprising:at least one processor; andat least one memory storing instructions which, when executed by the at least one processor, cause the UE to perform operations, the operations comprising:obtaining information that a disaster condition applies to a next generation radio access network (NG-RAN) of a first public land mobile network (PLMN) in which the UE is roaming, wherein the UE is restricted from accessing a first evolved universal mobile telecommunications system (UMTS) terrestrial radio access network (E-UTRAN) of the first PLMN;sending, to a radio resource control (RRC) layer of the UE based on the information that the disaster condition applies to the NG-RAN, a request to establish or resume a RRC connection toward an E-UTRAN, and an indication that the disaster condition applies, wherein the E-UTRAN is the first E-UTRAN of the first PLMN or a second E-UTRAN of a second PLMN;receiving, at the RRC layer from the E-UTRAN, broadcast information that includes barring information for the disaster condition; andperforming, at the RRC layer, an access barring check using the barring information.

2. The UE of claim 1, wherein the operations further comprise selecting, based on the information that the disaster condition applies to the NG-RAN, the first E-UTRAN or the second E-UTRAN as the E-UTRAN for the request to establish or resume the RRC connection.

3. The UE of claim 1 or claim 2, wherein the indication that the disaster condition applies comprises a call type set to a value indicating that that the disaster condition applies.

4. The UE of any of claims 1 to 3, wherein the indication that the disaster condition applies comprises an indication which is sent to the RRC layer in addition to a call type.

5. The UE of any of claims 1 to 4, wherein the barring information includes a barring factor, and wherein performing the access barring check comprises:generating a random number; andcomparing the barring factor to the random number to determine whether an access attempt to the E-UTRAN is barred or not barred.

6. The UE of claim 5, wherein the access attempt is barred when the random number is greater than or equal to the barring factor, and the access attempt is not barred when the random number is less than the barring factor.

7. The UE of any of claims 1 to 6, wherein the access barring check indicates an access attempt is not barred, andwherein the operations further comprise sending an RRC message to the E-UTRAN to establish or resume the RRC connection.

8. The UE of claim 7, wherein the operations further comprise generating an evolved packet system (EPS) mobility management (EMM) message for a disaster roaming service, andwherein the request to establish or resume a RRC connection toward the E-UTRAN comprises the EMM message for the RRC layer to send the EMM message over the RRC connection.

9. The UE of any of claims 1 to 8, wherein the request is sent to the RRC layer from an evolved packet system (EPS) mobility management (EMM) layer of the UE,wherein the access barring check indicates an access attempt is barred, andwherein the operations further comprise sending, from the RRC layer to the EMM layer, information that indicates the access attempt is barred.

10. A method performed by a user equipment (UE), the method comprising:obtaining information that a disaster condition applies to a next generation radio access network (NG-RAN) of a first public land mobile network (PLMN) in which the UE is roaming, wherein the UE is restricted from accessing a first evolved universal mobile telecommunications system (UMTS) terrestrial radio access network (E-UTRAN) of the first PLMN;sending, to a radio resource control (RRC) layer of the UE based on the information that the disaster condition applies to the NG-RAN, a request to establish or resume a RRC connection toward an E-UTRAN, and an indication that the disaster condition applies to the NG-RAN, wherein the E-UTRAN is the first E-UTRAN of the first PLMN or a second E-UTRAN of a second PLMN;receiving, at the RRC layer from the E-UTRAN, broadcast information that includes barring information for the disaster condition; andperforming, at the RRC layer, an access barring check using the barring information.

11. The method of claim 10, wherein the method further comprises selecting, based on the information that the disaster condition applies to the NG-RAN, the first E-UTRAN or the second E-UTRAN as the E-UTRAN for the request to establish or resume the RRC connection.

12. The method of claim 10 or claim 11, wherein the indication that the disaster condition applies comprises a call type set to a value indicating that that the disaster condition applies.

13. The method of any of claims 10 to 12, wherein the indication that the disaster condition applies comprises an indication which is sent to the RRC layer in addition to a call type.

14. The method of any of claims 10 to 13, wherein the barring information includes a barring factor, and wherein performing the access barring check comprises:generating a random number; andcomparing the barring factor to the random number to determine whether an access attempt to the E-UTRAN is barred or not barred.

15. The method of claim 14, wherein the access attempt is barred when the random number is greater than or equal to the barring factor, and the access attempt is not barred when the random number is less than the barring factor.

16. The method of any of claims 10 to 15, wherein the access barring check indicates an access attempt is not barred, andwherein the method further comprises sending an RRC message to the E-UTRAN to establish or resume the RRC connection.

17. The method of claim 16, wherein the method further comprises generating an evolved packet system (EPS) mobility management (EMM) message for a disaster roaming service, andwherein the request to establish or resume a RRC connection toward the E-UTRAN comprises the EMM message for the RRC layer to send the EMM message over the RRC connection.

18. The method of any of claims 10 to 17, wherein the request is sent to the RRC layer from an evolved packet system (EPS) mobility management (EMM) layer of the UE,wherein the access barring check indicates an access attempt is barred, andwherein the method further comprises sending, from the RRC layer to the EMM layer, information that indicates the access attempt is barred.

19. A computer-readable medium comprising instructions which, when executed by at least one processor, cause an apparatus to perform the method of any of claims 10 to 18.

20. A computer program comprising instructions which, when executed by at least one processor, cause an apparatus to perform the method of any of claims 10 to 18.

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