Patent Publication Number: US-2022217553-A1

Title: Communication method for handling network error

Description:
TECHNICAL FIELD 
     The present specification relates to mobile communication. 
     BACKGROUND 
     SAE (System Architecture Evolution) that has been performed based on 3GPP(3 rd  Generation Partnership Project) SA (Service and System Aspects) WG2 (working group 2) is research regarding network technology that aims to determine the structure of a network and to support mobility between heterogeneous networks in line with an LTE task of a 3GPP TSG (Technical Specification Group) RAN (radio access network) and is one of recent important standardization issues of 3GPP. SAE is a task for developing a 3GPP system into a system that supports various radio access technologies based on an IP (internet protocol), and the task has been carried out for the purpose of an optimized packet-based system which minimizes transmission delay with a more improved data transmission capability. 
     An Evolved Packet System (EPS) higher level reference model defined in 3GPP SA WG2 includes a non-roaming case and roaming cases having various scenarios, and for details therefor, reference can be made to 3GPP standard documents TS 23.401 and TS 23.402. A network configuration of  FIG. 1  has been briefly reconfigured from the EPS higher level reference model. 
       FIG. 1  shows the configuration of an evolved mobile communication network. 
     An Evolved Packet Core (EPC) may include various elements.  FIG. 1  illustrates a Serving Gateway (S-GW)  52 , a Packet Data Network Gateway (PDN GW)  53 , a Mobility Management Entity (MME)  51 , a Serving General Packet Radio Service (GPRS) Supporting Node (SGSN), and an enhanced Packet Data Gateway (ePDG) that correspond to some of the various elements. 
     The S-GW  52  is an element that operates at a boundary point between a Radio Access Network (RAN) and a core network and has a function of maintaining a data path between an eNodeB  22  and the PDN GW  53 . Furthermore, if a terminal (or User Equipment (UE) moves in a region in which service is provided by the eNodeB  22 , the S-GW  52  plays a role of a local mobility anchor point. That is, for mobility within an E-UTRAN (i.e., a Universal Mobile Telecommunications System (Evolved-UMTS) Terrestrial Radio Access Network defined after 3GPP release-8), packets can be routed through the S-GW  52 . Furthermore, the S-GW  52  may play a role of an anchor point for mobility with another 3GPP network (i.e., a RAN defined prior to 3GPP release-8, for example, a UTRAN or Global System for Mobile communication (GSM) (GERAN)/Enhanced Data rates for Global Evolution (EDGE) Radio Access Network). 
     The PDN GW (or P-GW)  53  corresponds to the termination point of a data interface toward a packet data network. The PDN GW  53  can support policy enforcement features, packet filtering, charging support, etc. Furthermore, the PDN GW (or P-GW)  53  can play a role of an anchor point for mobility management with a 3GPP network and a non-3GPP network (e.g., an unreliable network, such as an Interworking Wireless Local Area Network (I-WLAN), a Code Division Multiple Access (CDMA) network, or a reliable network, such as WiMax). 
     In the network configuration of  FIG. 1 , the S-GW  52  and the PDN GW  53  have been illustrated as being separate gateways, but the two gateways may be implemented in accordance with a single gateway configuration option. 
     The MME  51  is an element for performing the access of a terminal to a network connection and signaling and control functions for supporting the allocation, tracking, paging, roaming, handover, etc. of network resources. The MME  51  controls control plane functions related to subscribers and session management. The MME  51  manages numerous eNodeBs  22  and performs conventional signaling for selecting a gateway for handover to another 2G/3G networks. Furthermore, the MME  51  performs functions, such as security procedures, terminal-to-network session handling, and idle terminal location management. 
     The SGSN handles all packet data, such as a user&#39;s mobility management and authentication for different access 3GPP networks (e.g., a GPRS network and an UTRAN/GERAN). 
     The ePDG plays a role of a security node for an unreliable non-3GPP network (e.g., an I-WLAN and a Wi-Fi hotspot). 
     As described with reference to  FIG. 1 , a terminal (or UE) having an IP capability can access an IP service network (e.g., IMS), provided by a service provider (i.e., an operator), via various elements within an EPC based on non-3GPP access as well as based on 3GPP access. 
     Furthermore,  FIG. 1  shows various reference points (e.g., S1-U and S1-MME). In a 3GPP system, a conceptual link that connects two functions that are present in the different function entities of an E-UTRAN and an EPC is called a reference point. Table 1 below defines reference points shown in  FIG. 1 . In addition to the reference points shown in the example of Table 1, various reference points may be present depending on a network configuration. 
     
       
         
           
               
               
             
               
                 TABLE 1 
               
               
                   
               
               
                 REFERENCE 
                   
               
               
                 POINT 
                 DESCRIPTION 
               
               
                   
               
             
            
               
                 S1-MME 
                 A reference point for a control plane protocol between the E-UTRAN and the 
               
               
                   
                 MME 
               
               
                 S1-U 
                 A reference point between the E-UTRAN and the S-GW for path switching 
               
               
                   
                 between eNodeBs during handover and user plane tunneling per bearer 
               
               
                 S3 
                 A reference point between the MME and the SGSN that provides the exchange of 
               
               
                   
                 pieces of user and bearer information for mobility between 3GPP access networks 
               
               
                   
                 in idle and/or activation state. This reference point can be used intra-PLMN or 
               
               
                   
                 inter-PLMN (e.g. in the case of Inter-PLMN HO). 
               
               
                 S4 
                 A reference point between the SGW and the SGSN that provides related control 
               
               
                   
                 and mobility support between the 3GPP anchor functions of a GPRS core and the 
               
               
                   
                 S-GW. Furthermore, if a direct tunnel is not established, the reference point 
               
               
                   
                 provides user plane tunneling. 
               
               
                 S5 
                 A reference point that provides user plane tunneling and tunnel management 
               
               
                   
                 between the S-GW and the PDN GW. The reference point is used for S-GW 
               
               
                   
                 relocation due to UE mobility and if the S-GW needs to connect to a 
               
               
                   
                 non-collocated PDN GW for required PDN connectivity 
               
               
                 S11 
                 A reference point between the MME and the S-GW 
               
               
                 SGi 
                 A reference point between the PDN GW and the PDN. The PDN may be a public 
               
               
                   
                 or private PDN external to an operator or may be an intra-operator PDN, e.g., for 
               
               
                   
                 the providing of IMS services. This reference point corresponds to Gi for 3GPP 
               
               
                   
                 access. 
               
               
                   
               
            
           
         
       
     
     Among the reference points shown in  FIG. 1 , S2a and S2b correspond to non-3GPP interfaces. S2a is a reference point providing the user plane with related control and mobility support between a PDN GW and a reliable non-3GPP access. S2b is a reference point providing the user plane with mobility support and related control between a PDN GW and an ePDG. 
       FIG. 2  is an exemplary diagram showing the architecture of a common E-UTRAN and a common EPC. 
     As shown in  FIG. 2 , the eNodeB  20  can perform functions, such as routing to a gateway while RRC connection is activated, the scheduling and transmission of a paging message, the scheduling and transmission of a broadcast channel (BCH), the dynamic allocation of resources to UE in uplink and downlink, a configuration and providing for the measurement of the eNodeB  20 , control of a radio bearer, radio admission control, and connection mobility control. The EPC can perform functions, such as the generation of paging, the management of an LTE_IDLE state, the ciphering of a user plane, control of an EPS bearer, the ciphering of NAS signaling, and integrity protection. 
       FIG. 3  is an exemplary diagram showing the structure of a radio interface protocol in a control plane between UE and an eNodeB, and  FIG. 4  is another exemplary diagram showing the structure of a radio interface protocol in a control plane between UE and an eNodeB. 
     The radio interface protocol is based on a 3GPP radio access network standard. The radio interface protocol includes a physical layer, a data link layer, and a network layer horizontally, and it is divided into a user plane for the transmission of information and a control plane for the transfer of a control signal (or signaling). 
     The protocol layers may be classified into a first layer (L1), a second layer (L2), and a third layer (L3) based on three lower layers of the Open System Interconnection (OSI) reference model that is widely known in communication systems. 
     The layers of the radio protocol of the control plane shown in  FIG. 3  and the radio protocol in the user plane of  FIG. 4  are described below. 
     The physical layer PHY, that is, the first layer, provides information transfer service using physical channels. The PHY layer is connected to a Medium Access Control (MAC) layer placed in a higher layer through a transport channel, and data is transferred between the MAC layer and the PHY layer through the transport channel Furthermore, data is transferred between different PHY layers, that is, PHY layers on the sender side and the receiver side, through the PHY layer. 
     A physical channel is made up of multiple subframes on a time axis and multiple subcarriers on a frequency axis. Here, one subframe is made up of a plurality of symbols and a plurality of subcarriers on the time axis. One subframe is made up of a plurality of resource blocks, and one resource block is made up of a plurality of symbols and a plurality of subcarriers. A Transmission Time Interval (TTI), that is, a unit time during which data is transmitted, is 1 ms corresponding to one subframe. 
     In accordance with 3GPP LTE, physical channels that are present in the physical layer of the sender side and the receiver side can be divided into a Physical Downlink Shared Channel (PDSCH) and a Physical Uplink Shared Channel (PUSCH), that is, data channels, and a Physical Downlink Control Channel (PDCCH), a Physical Control Format Indicator Channel (PCFICH), a Physical Hybrid-ARQ Indicator Channel (PHICH), and a Physical Uplink Control Channel (PUCCH), that is, control channels. 
     A PCFICH that is transmitted in the first OFDM symbol of a subframe carries a Control Format Indicator (CFI) regarding the number of OFDM symbols (i.e., the size of a control region) used to send control channels within the subframe. A wireless device first receives a CFI on a PCFICH and then monitors PDCCHs. 
     Unlike a PDCCH, a PCFICH is transmitted through the fixed PCFICH resources of a subframe without using blind decoding. 
     A PHICH carries positive-acknowledgement (ACK)/negative-acknowledgement (NACK) signals for an uplink (UL) Hybrid Automatic Repeat reQuest (HARQ). ACK/NACK signals for UL data on a PUSCH that is transmitted by a wireless device are transmitted on a PHICH. 
     A Physical Broadcast Channel (PBCH) is transmitted in four former OFDM symbols of the second slot of the first subframe of a radio frame. The PBCH carries system information that is essential for a wireless device to communicate with an eNodeB, and system information transmitted through a PBCH is called a Master Information Block (MIB). In contrast, system information transmitted on a PDSCH indicated by a PDCCH is called a System Information Block (SIB). 
     A PDCCH can carry the resource allocation and transport format of a downlink-shared channel (DL-SCH), information about the resource allocation of an uplink shared channel (UL-SCH), paging information for a PCH, system information for a DL-SCH, the resource allocation of an upper layer control message transmitted on a PDSCH, such as a random access response, a set of transmit power control commands for pieces of UE within a specific UE group, and the activation of a Voice over Internet Protocol (VoIP). A plurality of PDCCHs can be transmitted within the control region, and UE can monitor a plurality of PDCCHs. A PDCCH is transmitted on one Control Channel Element (CCE) or an aggregation of multiple contiguous CCEs. A CCE is a logical allocation unit used to provide a PDCCH with a coding rate according to the state of a radio channel A CCE corresponds to a plurality of resource element groups. The format of a PDCCH and the number of bits of a possible PDCCH are determined by a relationship between the number of CCEs and a coding rate provided by CCEs. 
     Control information transmitted through a PDCCH is called Downlink Control Information (DCI). DCI can include the resource allocation of a PDSCH (also called a downlink (DL) grant)), the resource allocation of a PUSCH (also called an uplink (UL) grant), a set of transmit power control commands for pieces of UE within a specific UE group, and/or the activation of a Voice over Internet Protocol (VoIP). 
     Several layers are present in the second layer. First, a Medium Access Control (MAC) layer functions to map various logical channels to various transport channels and also plays a role of logical channel multiplexing for mapping multiple logical channels to one transport channel. The MAC layer is connected to a Radio Link Control (RLC) layer, that is, a higher layer, through a logical channel The logical channel is basically divided into a control channel through which information of the control plane is transmitted and a traffic channel through which information of the user plane is transmitted depending on the type of transmitted information. 
     The RLC layer of the second layer functions to control a data size that is suitable for sending, by a lower layer, data received from a higher layer in a radio section by segmenting and concatenating the data. Furthermore, in order to guarantee various types of QoS required by radio bearers, the RLC layer provides three types of operation modes: a Transparent Mode (TM), an Un-acknowledged Mode (UM), and an Acknowledged Mode (AM). In particular, AM RLC performs a retransmission function through an Automatic Repeat and Request (ARQ) function for reliable data transmission. 
     The Packet Data Convergence Protocol (PDCP) layer of the second layer performs a header compression function for reducing the size of an IP packet header containing control information that is relatively large in size and unnecessary in order to efficiently send an IP packet, such as IPv4 or IPv6, in a radio section having a small bandwidth when sending the IP packet. Accordingly, transmission efficiency of the radio section can be increased because only essential information is transmitted in the header part of data. Furthermore, in an LTE system, the PDCP layer also performs a security function. The security function includes ciphering for preventing the interception of data by a third party and integrity protection for preventing the manipulation of data by a third party. 
     A Radio Resource Control (RRC) layer at the highest place of the third layer is defined only in the control plane and is responsible for control of logical channels, transport channels, and physical channels in relation to the configuration, re-configuration, and release of Radio Bearers (RBs). Here, the RB means service provided by the second layer in order to transfer data between UE and an E-UTRAN. 
     If an RRC connection is present between the RRC layer of UE and the RRC layer of a wireless network, the UE is in an RRC_CONNECTED state. If not, the UE is in an RRC_IDLE state. 
     An RRC state and an RRC connection method of UE are described below. The RRC state means whether or not the RRC layer of UE has been logically connected to the RRC layer of an E-UTRAN. If the RRC layer of UE is logically connected to the RRC layer of an E-UTRAN, it is called the RRC_CONNECTED state. If the RRC layer of UE is not logically connected to the RRC layer of an E-UTRAN, it is called the RRC_IDLE state. Since UE in the RRC_CONNECTED state has an RRC connection, an E-UTRAN can check the existence of the UE in a cell unit, and thus control the UE effectively. In contrast, if UE is in the RRC_IDLE state, an E-UTRAN cannot check the existence of the UE, and a core network is managed in a Tracking Area (TA) unit, that is, an area unit greater than a cell. That is, only the existence of UE in the RRC_IDLE state is checked in an area unit greater than a cell. In such a case, the UE needs to shift to the RRC_CONNECTED state in order to be provided with common mobile communication service, such as voice or data. Each TA is classified through Tracking Area Identity (TAI). UE can configure TAI through Tracking Area Code (TAC), that is, information broadcasted by a cell. 
     When a user first turns on the power of UE, the UE first searches for a proper cell, establishes an RRC connection in the corresponding cell, and registers information about the UE with a core network. Thereafter, the UE stays in the RRC_IDLE state. The UE in the RRC_IDLE state (re)selects a cell if necessary and checks system information or paging information. This process is called camp on. When the UE in the RRC_IDLE state needs to establish an RRC connection, the UE establishes an RRC connection with the RRC layer of an E-UTRAN through an RRC connection procedure and shifts to the RRC_CONNECTED state. A case where the UE in the RRC_IDLE state needs to establish with an RRC connection includes multiple cases. The multiple cases may include, for example, a case where UL data needs to be transmitted for a reason, such as a call attempt made by a user and a case where a response message needs to be transmitted in response to a paging message received from an E-UTRAN. 
     A Non-Access Stratum (NAS) layer placed over the RRC layer performs functions, such as session management and mobility management. 
     The NAS layer shown in  FIG. 3  is described in detail below. 
     Evolved Session Management (ESM) belonging to the NAS layer performs functions, such as the management of default bearers and the management of dedicated bearers, and ESM is responsible for control that is necessary for UE to use PS service from a network. Default bearer resources are characterized in that they are allocated by a network when UE first accesses a specific Packet Data Network (PDN) or accesses a network. Here, the network allocates an IP address available for UE so that the UE can use data service and the QoS of a default bearer. LTE supports two types of bearers: a bearer having Guaranteed Bit Rate (GBR) QoS characteristic that guarantees a specific bandwidth for the transmission and reception of data and a non-GBR bearer having the best effort QoS characteristic without guaranteeing a bandwidth. A default bearer is assigned a non-GBR bearer, and a dedicated bearer may be assigned a bearer having a GBR or non-GBR QoS characteristic. 
     In a network, a bearer assigned to UE is called an Evolved Packet Service (EPS) bearer. When assigning an EPS bearer, a network assigns one ID. This is called an EPS bearer ID. One EPS bearer has QoS characteristics of a Maximum Bit Rate (MBR) and a Guaranteed Bit Rate (GBR) or an Aggregated Maximum Bit Rate (AMBR). 
       FIG. 5 a    is a flowchart illustrating a random access process in 3GPP LTE. 
     The random access process is used for UE  10  to obtain UL synchronization with a base station, that is, an eNodeB  20 , or to be assigned UL radio resources. 
     The UE  10  receives a root index and a physical random access channel (PRACH) configuration index from the eNodeB  20 . 64 candidate random access preambles defined by a Zadoff-Chu (ZC) sequence are present in each cell. The root index is a logical index that is used for the UE to generate the 64 candidate random access preambles. 
     The transmission of a random access preamble is limited to specific time and frequency resources in each cell. The PRACH configuration index indicates a specific subframe on which a random access preamble can be transmitted and a preamble format. 
     The UE  10  sends a randomly selected random access preamble to the eNodeB  20 . Here, the UE  10  selects one of the 64 candidate random access preambles. Furthermore, the UE selects a subframe corresponding to the PRACH configuration index. The UE  10  sends the selected random access preamble in the selected subframe. 
     The eNodeB  20  that has received the random access preamble sends a Random Access Response (RAR) to the UE  10 . The random access response is detected in two steps. First, the UE  10  detects a PDCCH masked with a random access-RNTI (RA-RNTI). The UE  10  receives a random access response within a Medium Access Control (MAC) Protocol Data Unit (PDU) on a PDSCH that is indicated by the detected PDCCH. 
       FIG. 5 b    illustrates a connection process in a radio resource control (RRC) layer. 
       FIG. 5 b    shows an RRC state depending on whether there is an RRC connection. The RRC state denotes whether the entity of the RRC layer of UE  10  is in logical connection with the entity of the RRC layer of eNodeB  20 , and if yes, it is referred to as RRC connected state, and if no as RRC idle state. 
     In the connected state, UE  10  has an RRC connection, and thus, the E-UTRAN may grasp the presence of the UE on a cell basis and may thus effectively control UE  10 . In contrast, UE  10  in the idle state cannot grasp eNodeB  20  and is managed by a core network on the basis of a tracking area that is larger than a cell. The tracking area is a set of cells. That is, UE  10  in the idle state is grasped for its presence only on a larger area basis, and the UE should switch to the connected state to receive a typical mobile communication service such as voice or data service. 
     When the user turns on UE  10 , UE  10  searches for a proper cell and stays in idle state in the cell. UE  10 , when required, establishes an RRC connection with the RRC layer of eNodeB  20  through an RRC connection procedure and transits to the RRC connected state. 
     There are a number of situations where the UE staying in the idle state needs to establish an RRC connection, for example, when the user attempts to call or when uplink data transmission is needed, or when transmitting a message responsive to reception of a paging message from the EUTRAN. 
     In order for the idle UE  10  to be RRC connected with eNodeB  20 , UE  10  needs to perform the RRC connection procedure as described above. The RRC connection procedure generally comes with the process in which UE  10  transmits an RRC connection request message to eNodeB  20 , the process in which eNodeB  20  transmits an RRC connection setup message to UE  10 , and the process in which UE  10  transmits an RRC connection setup complete message to eNodeB  20 . The processes are described in further detail with reference to  FIG. 6 . 
     1) The idle UE  10 , when attempting to establish an RRC connection, e.g., for attempting to call or transmit data or responding to paging from eNodeB  20 , sends an RRC connection request message to eNodeB  20 . 
     2) When receiving the RRC connection message from UE  10 , eNodeB  20  accepts the RRC connection request from UE  10  if there are enough radio resources, and eNodeB  20  sends a response message, RRC connection setup message, to UE  10 . 
     3) When receiving the RRC connection setup message, UE  10  transmits an RRC connection setup complete message to eNodeB  20 . If UE  10  successfully transmits the RRC connection setup message, UE  10  happens to establish an RRC connection with eNodeB  20  and switches to the RRC connected state. 
     &lt;Network Failure&gt; 
     On the other hand, a failure may occur in the base station of the first public land mobile network (PLMN) by the first operator, and a situation may occur in which a mobile communication service cannot be provided any longer through the corresponding base station. 
     A simple failure can be restored within a short period of time, but when a failure occurs due to fire, flooding, etc., it may not be restored for hours or days. In this case, user may take inconvenience for simple communication, but interruption of important communication (eg, emergency call (119 or 911 call) or corporate VPN communication) may cause a major problem. 
     Therefore, when a failure occurs in the first PLMN by the first operator, there is a need for a method in which a subscriber of the first operator can be provided with a communication service. For example, when a failure occurs in the first PLMN by the first operator, another second operator may provide a service for the subscribers of the first operator on behalf of the first operator. 
     However, there is a problem that a technical method for this has not been proposed so far. 
     SUMMARY 
     Accordingly, one disclosure of this specification is to propose a scheme capable of solving the aforementioned problems. 
     In order to achieve the above object, one disclosure of the present specification provides a communication method for handling a network failure performed by a terminal. The terminal may receive information about a second PLMN to which the terminal is subscribed from a base station in a first public land mobile network (PLMN). The terminal may access the first PLMN through a base station in the first PLMN based on the information on the second PLMN. The terminal may display information informing of a failure occurring in the second PLMN on the display of the terminal. 
     According to the embodiments of the present specification, the problems in the related art can be solved. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows the configuration of an evolved mobile communication network. 
         FIG. 2  is an exemplary diagram showing the architecture of a common E-UTRAN and a common EPC. 
         FIG. 3  is an exemplary diagram showing the structure of a radio interface protocol in a control plane between UE and an eNodeB. 
         FIG. 4  is another exemplary diagram showing the structure of a radio interface protocol in a control plane between UE and an eNodeB. 
         FIG. 5 a    is a flowchart illustrating a random access process in 3GPP LTE. 
         FIG. 5 b    illustrates a connection process in a radio resource control (RRC) layer. 
         FIG. 6  shows a connection between an EPC and an IP Multimedia Subsystem (IMS). 
         FIG. 7  illustrates a voice over LTE (VoLTE) roaming architecture. 
         FIG. 8  is an exemplary signal flow diagram illustrating a process of performing IMS registration in a HR (Home Routed) manner in a situation in which the UE roams to a visited network. 
         FIG. 9  is a structural diagram of a next-generation mobile communication network. 
         FIG. 10  is an exemplary diagram illustrating a predicted structure of a next generation mobile communication in terms of a node. 
         FIG. 11  illustrates an architecture that allows the UE to simultaneously access two data networks using one PDU session. 
         FIG. 12  is another exemplary diagram showing a structure of a radio interface protocol between a UE and a gNB. 
         FIG. 13  is a block diagram of a UE according to an embodiment of the present disclosure. 
         FIG. 14  is a block diagram showing the configuration of the terminal shown in  FIG. 13  in more detail. 
         FIG. 15  shows an example of an EPS network structure related to the disclosure of the present specification. 
         FIG. 16  shows an example of an EPS network structure related to the disclosure of the present specification. 
         FIGS. 17A and 17B  show an embodiment in which a first example of the disclosure of the present specification is applied to an EPS. 
         FIGS. 18A and 18B  show an embodiment in which the first example of the disclosure of the present specification is applied to 5GS. 
         FIGS. 19A and 19B  show an embodiment in which a second example of the disclosure of the present specification is applied to an EPS. 
         FIGS. 20A and 20B  show an embodiment in which a second example of the disclosure of the present specification is applied to 5GS. 
         FIGS. 21A and 21B  show an embodiment in which a third example of the disclosure of the present specification is applied to EPS. 
         FIGS. 22A and 22B  show an embodiment in which a third example of the disclosure of the present specification is applied to 5GS. 
         FIG. 23  is a flowchart illustrating an example of an operation of a terminal. 
         FIG. 24  is a first exemplary diagram illustrating a screen of a terminal according to an embodiment. 
         FIG. 25  is a second exemplary diagram illustrating a screen of a terminal according to an embodiment. 
         FIG. 26  is a third exemplary diagram illustrating a screen of a terminal according to an embodiment. 
         FIG. 27  is a fourth exemplary diagram illustrating a screen of a terminal according to an embodiment. 
         FIG. 28  is a fifth exemplary diagram illustrating a screen of a terminal according to an embodiment. 
         FIG. 29  is a sixth exemplary diagram illustrating a screen of a terminal according to an embodiment. 
         FIG. 30  is a seventh exemplary diagram illustrating a screen of a terminal according to an embodiment. 
         FIG. 31A  is an eighth exemplary view illustrating a screen of a terminal according to an embodiment. 
         FIG. 31B  is a ninth exemplary diagram illustrating a screen of a terminal according to an embodiment. 
         FIG. 32  is a tenth exemplary diagram illustrating a screen of a terminal according to an embodiment. 
         FIG. 33  illustrates a wireless communication system according to an embodiment. 
         FIG. 34  illustrates an example of 5G use scenarios. 
         FIG. 35  shows an AI system  1  according to an embodiment. 
     
    
    
     DESCRIPTION OF EXEMPLARY EMBODIMENTS 
     The technical terms used herein are used to merely describe specific embodiments and should not be construed as limiting the presented specification. Further, the technical terms used herein should be, unless defined otherwise, interpreted as having meanings generally understood by those skilled in the art but not too broadly or too narrowly. Further, the technical terms used herein, which are determined not to exactly represented the spirit of the specification, should be replaced by or understood by such technical terms as being able to be exactly understood by those skilled in the art. Further, the general terms used herein should be interpreted in the context as defined in the dictionary, but not in an excessively narrowed manner. 
     Furthermore, the expression of the singular number in the specification includes the meaning of the plural number unless the meaning of the singular number is definitely different from that of the plural number in the context. In the following description, the term ‘include’ or ‘have’ may represented the existence of a feature, a number, a step, an operation, a component, a part or the combination thereof described in the specification, and may not exclude the existence or addition of another feature, another number, another step, another operation, another component, another part or the combination thereof. 
     The terms ‘first’ and ‘second’ are used for the purpose of explanation about various components, and the components are not limited to the terms ‘first’ and ‘second’. The terms ‘first’ and ‘second’ are only used to distinguish one component from another component. For example, a first component may be named as a second component without deviating from the scope of the presented specification. 
     It will be understood that when an element or layer is referred to as being “connected to” or “coupled to” another element or layer, it can be directly connected or coupled to the other element or layer or intervening elements or layers may be presented. In contrast, when an element is referred to as being “directly connected to” or “directly coupled to” another element or layer, there are no intervening elements or layers presented. 
     Hereinafter, exemplary embodiments of the presented specification will be described in greater detail with reference to the accompanying drawings. In describing the presented specification, for ease of understanding, the same reference numerals are used to denote the same components throughout the drawings, and repetitive description on the same components will be omitted. Detailed description on well-known arts which are determined to make the gist of the specification unclear will be omitted. The accompanying drawings are provided to merely make the spirit of the specification readily understood, but not should be intended to be limiting of the specification. It should be understood that the spirit of the specification may be expanded to its modifications, replacements or equivalents in addition to what is shown in the drawings. 
     In the accompanying drawings, UE (User Equipment) is illustrated by way of example, but the illustrated UE may be referred to by terms such as a terminal (Terminal), ME (Mobile Equipment), and the like. In addition, the UE may be a portable device such as a notebook computer, a mobile phone, a PDA, a smart phone, a multimedia device, or the like, or may be a non-portable device such as a PC or a vehicle-mounted device. 
     Definition of Terms 
     For better understanding, the terms used herein are briefly defined before going to the detailed description of the specification with reference to the accompanying drawings. 
     A GERAN: an abbreviation of a GSM EDGE Radio Access Network, and it refers to a radio access section that connects a core network and UE by GSM/EDGE. 
     A UTRAN: an abbreviation of a Universal Terrestrial Radio Access Network, and it refers to a radio access section that connects the core network of the 3rd generation mobile communication and UE. 
     An E-UTRAN: an abbreviation of an Evolved Universal Terrestrial Radio Access Network, and it refers to a radio access section that connects the core network of the 4th generation mobile communication, that is, LTE, and UE. 
     An UMTS is an abbreviation of a Universal Mobile Telecommunication System, and it refers to the core network of the 3rd generation mobile communication. 
     UE/MS is an abbreviation of User Equipment/Mobile Station, and it refers to a terminal device. 
     An EPS is an abbreviation of an Evolved Packet System, and it refers to a core network supporting a Long Term Evolution (LTE) network and to a network evolved from an UMTS. 
     A PDN is an abbreviation of a Public Data Network, and it refers to an independent network where a service for providing service is placed. 
     A PDN connection refers to a connection from UE to a PDN, that is, an association (or connection) between UE represented by an IP address and a PDN represented by an APN. 
     A PDN-GW is an abbreviation of a Packet Data Network Gateway, and it refers to a network node of an EPS network which performs functions, such as the allocation of a UE IP address, packet screening &amp; filtering, and the collection of charging data. 
     A Serving gateway (Serving GW) is a network node of an EPS network which performs functions, such as mobility anchor, packet routing, idle mode packet buffering, and triggering an MME to page UE. 
     A Policy and Charging Rule Function (PCRF): The node of an EPS network which performs a policy decision for dynamically applying QoS and a billing policy that are different for each service flow. 
     An Access Point Name (APN) is the name of an access point that is managed in a network and provides to UE. That is, an APN is a character string that denotes or identifies a PDN. Requested service or a network (PDN) is accessed via P-GW. An APN is a name (a character string, e.g., ‘internet.mnc012.mcc345.gprs’) previously defined within a network so that the P-GW can be searched for. 
     A Tunnel Endpoint Identifier (TEID): The end point ID of a tunnel set between nodes within a network, and it is set for each bearer unit of each UE. 
     A NodeB is an eNodeB of a UMTS network and installed outdoors. The cell coverage of the NodeB corresponds to a macro cell. 
     An eNodeB is an eNodeB of an Evolved Packet System (EPS) and is installed outdoors. The cell coverage of the eNodeB corresponds to a macro cell. 
     An (e)NodeB is a term that denotes a NodeB and an eNodeB. 
     An MME is an abbreviation of a Mobility Management Entity, and it functions to control each entity within an EPS in order to provide a session and mobility for UE. 
     A session is a passage for data transmission, and a unit thereof may be a PDN, a bearer, or an IP flow unit. The units may be classified into a unit of the entire target network (i.e., an APN or PDN unit) as defined in 3GPP, a unit (i.e., a bearer unit) classified based on QoS within the entire target network, and a destination IP address unit. 
     A PDN connection is a connection from UE to a PDN, that is, an association (or connection) between UE represented by an IP address and a PDN represented by an APN. It means a connection between entities (i.e., UE-PDN GW) within a core network so that a session can be formed. 
     UE context is information about the situation of UE which is used to manage the UE in a network, that is, situation information including an UE ID, mobility (e.g., a current location), and the attributes of a session (e.g., QoS and priority) 
     NAS (Non-Access-Stratum): A higher stratum of a control plane between a UE and an MME. The NAS supports mobility management, session management, IP address management, etc., between the UE and the network. 
     RAT: an abbreviation of Radio Access Technology. Means GERAN, UTRAN, E-UTRAN, etc. 
     Each of embodiments proposed herein may be implemented solely, but the embodiments may be implemented in combination. 
       FIG. 6  shows a connection between an EPC and an IP Multimedia Subsystem (IMS). 
     Refer to  FIG. 6 , in the EPC, the MME  510 , the S-GW  520 , the P-GW  530   a  connected to the IMS, the P-GW  530   b  connected to the Internet, and A Policy and Charging Rule Function (PCRF)  580  connected to the P-GW  530   b  and a traffic detection function (TDF)  590  connected to the PCRF  580  are shown. 
     The TDF  590  detects the application and reports the detected application and description information about the service data flow of the application to the PCRF  580 . The TDF  590  supports solicited application reporting and/or unsolicited application reporting. 
     IMS is a network technology that enables packet switching (PS: Packet Switching) based on IP (Internet Protocol) to not only wired terminals but also wireless terminals, and has been proposed to connect both the wired terminals and wireless terminals via (All-IP). 
     The IMS-based network includes CSCF (Call Session Control Function) and IBCF (Interconnection Border Control Functions)  620  for handling control signaling, registration, and session procedures. The CSCF may include a Proxy-CSCF (P-CSCF)  61  and a Serving-CSCF (S-CSCF)  630 . In addition, the CSCF may include an Interrogating-CSCF (I-CSCF). The P-CSCF  610  operates as a first access point for user equipment (UE) in an IMS-based network. Then, the S-CSCF  630  processes a session in the IMS network. That is, the S-SCSF  630  is an entity responsible for routing signaling and routes a session in the IMS network. And, the I-CSCF operates as an access point with other entities in the IMS network. 
     Under the above IMS, an IP-based session is controlled by a session initiation protocol (SIP). The SIP is a protocol for controlling a session, the SIP is a protocol indicating a procedure for terminals wanting to communicate to identify each other and find their location, create a multimedia service session between them, or delete and change the created session. The SIP uses a SIP Uniform Resource Identifier (URI) similar to an e-mail address to distinguish each user, so that a service can be provided without being dependent on an IP (Internet Protocol) address. These SIP messages are control messages, but are transmitted between the UE and the IMS network through the EPC user plane. 
     Referring to  FIG. 6 , the first P-GW  530   a  of the EPC is connected to the P-CSCF  610  of the IMS, the P-CSCF  610  is connected to the IBCF  620 , and the IBCF  620  is connected to the S-CSCF ( 630 ). 
     In addition, the second P-GW  530   b  of the EPC is connected to the network of the Internet service provider. 
       FIG. 7  illustrates a voice over LTE (VoLTE) roaming architecture. 
     As illustrated in  FIG. 7 , the VoLTE roaming architecture includes a home routed (HR) architecture and a local breakout (LBO) architecture. 
     According to the LBO architecture, an IMS signal transmitted from a UE is transmitted to an S-CSCF in a home public land mobile network (H-PLMN) via an S-GW/P-GW/P-CSCF in a visited PLMN (V-PLMN). 
     In the HR architecture, the IMS signal is transmitted to the S-CSCF via the S-GW in the V-PLMN and a P-GW/P-CSCF in the H-PLMN. 
       FIG. 8  is an exemplary signal flow diagram illustrating a process of performing IMS registration in a HR (Home Routed) manner in a situation in which the UE roams to a visited network. 
     As can be seen with reference to  FIG. 8 , the UE  100  is in a roaming state in the visited network. 
     First, the UE  100  located in the visited network generates an IMS PDN with P-GW in the home network through the S-GW  520   b  in the visited network. Here, the IMS PDN may be a PDN for an IMS service, a PDN of a well-known IMS APN, a PDN for a Voice over LTE service, or the like. 
     1) Next, when the UE  100  transmits a SIP-based REGISTER message to the S-GW  520   b  in the visited network to perform IMS registration, the S-GW  520   b  in the visited network transmits the message to the P-CSCF  610   a  in the home network. 
     2) The P-CSCF  610   a  forwards the message to the I-CSCF  640   a.    
     3) to 4) The I-CSCF  640   a  obtains user information from the HSS  540   a  in the home network. 
     5) Next, the I-CSCF  640   a  transmits the SIP-based REGISTER message to the S-CSCF  630   a.    
     6) to 7) The S-CSCF  630   a  obtains user information from the HSS. 
     8) Subsequently, the S-CSCF  630   a  performs service control for registration of the UE. 
     9) to 11) If the registration of the UE is successful, the S-CSCF  630   a  transmits a 200 OK message. 
     &lt;Next Generation Mobile Communication System Architecture&gt; 
     With the success of Evolved Universal Terrestrial Radio Access Network (E-UTRAN) for the fourth-generation mobile communication which is Long Term Evolution (LTE)/LTE-Advanced (LTE-A), the next generation mobile communication, which is the fifth-generation (so called 5G) mobile communication, has been attracting attentions and more and more researches are being conducted. 
     The fifth-generation communication defined by the International Telecommunication Union (ITU) refers to providing a maximum data transmission speed of 20 Gbps and a maximum transmission speed of 100 Mbps per user in anywhere. It is officially called “IMT-2020” and aims to be released around the world in 2020. 
     The ITU proposes three usage scenarios, for example, enhanced Mobile BroadBand (eMBB), massive Machine Type Communication (mMTC) and Ultra Reliable and Low Latency Communications (URLLC). 
     First, URLLC relates to usage scenarios requiring high reliability and low latency. For example, services such as autonomous driving, factory automation, and augmented reality require high reliability and low latency (eg, latency of 1 ms or less). Currently, the delay time of 4G (LTE) is statistically 21-43 ms (best 10%) and 33-75 ms (median). This is insufficient to support services requiring latency of less than 1 ms. 
     Next, the eMBB usage scenario relates to a usage scenario requiring mobile ultra-wideband. 
     This ultra-wideband high-speed service seems difficult to be accommodated by the core network designed for the existing LTE/LTE-A. 
     Therefore, in the so-called 5G mobile communication, redesign of the core network is urgently required. 
       FIG. 9  is a structural diagram of a next-generation mobile communication network. 
     5GC(5G Core) may include various components, part of which are shown in  FIG. 9 , including an access and mobility management function (AMF)  410 , a session management function (SMF)  420 , a policy control function (PCF)  430 , a User Plane Function (UPF)  440 , an application function (AF)  450 , a unified data management (UDM) data network  460 , and a non-3GPP interworking function (N3IWF)  490 . 
     A UE  100  is connected to a data network via the UPF  440  through a Next Generation Radio Access Network (NG-RAN) including the gNB  20 . 
     The UE  100  may be provided with a data service even through untrusted non-3GPP access, e.g., a wireless local area network (WLAN). In order to connect the non-3GPP access to a core network, the N3IWF  490  may be deployed. 
       FIG. 10  is an exemplary diagram illustrating a predicted structure of a next generation mobile communication in terms of a node. 
     Referring to  FIG. 10 , the UE is connected to a data network (DN) through a next generation RAN (Radio Access Network). 
     The Control Plane Function (CPF) node shown in  FIG. 10  may perform all or part of the Mobility Management Entity (MME) function of the fourth generation mobile communication, and all or a part of the control plane function of the Serving Gateway (S-GW) and the PDN-gateway (P-GW) of the fourth generation mobile communication. The CPF node includes an Access and Mobility Management Function (AMF) node and a Session Management Function (SMF) node. 
     The user plane function (UPF) node shown in the drawing is a type of a gateway over which user data is transmitted and received. The UPF node may perform all or part of the user plane functions of the S-GW and the P-GW of the fourth generation mobile communication. 
     The Policy Control Function (PCF) node shown in  FIG. 10  is configured to control a policy of the service provider. 
     The illustrated Application Function (AF) node refers to a server for providing various services to the UE. 
     The Unified Data Management (UDM) node as shown refers to a type of a server that manages subscriber information, such as a Home Subscriber Server (HSS) of 4th generation mobile communication. The UDM node stores and manages the subscriber information in the Unified Data Repository (UDR). 
     The Authentication Server Function (AUSF) node as shown authenticates and manages the UE. 
     The Network Slice Selection Function (NSSF) node as shown refers to a node for performing network slicing as described below. 
     In  FIG. 10 , UE may access to 2 data networks by using multiple PDU (Protocol Data Unit) session. 
       FIG. 11  illustrates an architecture that allows the UE to simultaneously access two data networks using one PDU session. 
       FIG. 11  illustrates an architecture that allows the UE to simultaneously access two data networks using one PDU session. 
       FIG. 12  is another exemplary diagram showing a structure of a radio interface protocol between a UE and a gNB. 
     The radio interface protocol is based on the 3GPP radio access network standard. The radio interface protocol is horizontally composed of a physical layer, a data link layer, and a network layer, and is vertically divided into a user plane for transmission of data information and a control plane for transfer of control signal (signaling). 
     The protocol layers may be divided into L1 (first layer), L2 (second layer), and L3 layer (third layer) based on the lower three layers of the open system interconnection (OSI) reference model widely known in communication systems. 
     Meanwhile, in  FIG. 12 , the RRC layer, the RLC layer, the MAC layer, and the PHY layer located below the NAS layer are collectively referred to as an access stratum (AS). 
     &lt;Problems to be Solved by the Disclosure of this Specification&gt; 
     In the present specification, a situation in which a mobile communication service can no longer be provided through the base station due to a failure in the base station of the first PLMN by the first operator is described. Until the physical recovery of the corresponding base station is made, it is assumed that the base station of the second PLMN by the second operator broadcasts the SIB message temporarily (for example, hours or days, etc.) by including information on the first PLMN by a third party (other company) (ie, the second operator) in order to provide a service on behalf of the first operator in the corresponding failure area. 
     In this case, the third party (other company) subscription terminal that has received the broadcast information accesses the network in the same way as when accessing the HPLMN, whereas from the network point of view, the same shape as the network serving the roaming terminal is made. That is, from a network point of view, in order to cope with a failure occurring in the first PLMN of the first operator, the network node of the second PLMN (eg, VPLMN) of the second operator may perform connection to the network node of the first PLMN (eg, HPLMN), and thus a route such as HR (Home Routed) roaming can be used. This may cause the following problems. 
     Accordingly, if an appropriate operation of the network (the first PLMN) is not performed, the utilization of network resources such as signaling waste and the user&#39;s service experience may be lowered. For example, since the terminal does not recognize the roaming situation, it may not understand the charging policy or the restrictions in the roaming situation, and may transmit various requests (requests that the network is likely to reject) to the network. For this reason, even if the network rejects the request transmitted by the terminal to control communication with the terminal roaming in the network, utilization of network resources such as signaling waste and the user&#39;s service experience may be lowered. 
     &lt;Disclosure of the Present Specification&gt; 
     The disclosure of the present specification may be implemented by a combination of one or more of the following configurations. In the case of the embodiment below, an embodiment is shown to show each individual configuration, but an embodiment in which one or more combinations are configured together may be implemented. 
     &lt;Device to which the Disclosure of the Present Specification can be Applied&gt; 
     Hereinafter, an apparatus to which the disclosure of the present specification can be applied will be described. 
       FIG. 13  is a block diagram of a UE according to an embodiment of the present disclosure. 
     As can be seen with reference to  FIG. 13 , a UE includes a memory  1010 , a processor  1020 , a transceiver  1031 , a power management module  1091 , a battery  1092 , a display  1041 , an input unit  1053 , a speaker  1042 , a microphone  1052 , a subscriber identification module (SIM) card, and one or more antennas. 
     The processor  1020  may be configured to implement the proposed function, process and/or method described in the present disclosure. Layers of a wireless interface protocol may be implemented in the processor  1020 . The processor  1020  may include application-specific integrated circuit (ASIC), other chipset, logical circuit and/or data processing apparatus. The processor  1020  may be an application processor (AP). The processor  1020  may include at least one of a digital signal processor (DSP), a central processing unit (CPU), a graphics processing unit (GPU) and a modulator and demodulator (Modem). An example of the processor  1020  may be SNAPDRAGON™ series processor manufactured by Qualcomm®, EXYNOS™ series processor manufactured by Samsung®, A series processor manufactured by Apple®, HELIO™ series processor manufactured by MediaTek®, ATOM™ series processor manufactured by INTEL®, or the corresponding next generation processor. 
     The power management module  1091  manages a power for the processor  1020  and/or the transceiver  1031 . The battery  1092  supplies power to the power management module  1091 . The display  1041  outputs the result processed by the processor  1020 . The input unit  1053  receives an input to be used by the processor  1020 . The input unit  1053  may be displayed on the display  1041 . The SIM card is an integrated circuit used to safely store international mobile subscriber identity (IMSI) used for identifying a subscriber in a mobile telephoning apparatus such as a mobile phone and a computer and the related key. Many types of contact address information may be stored in the SIM card. 
     The memory  1010  is coupled with the processor  1020  in a way to operate and stores various types of information to operate the processor  1020 . The memory may include read-only memory (ROM), random access memory (RAM), flash memory, a memory card, a storage medium, and/or other storage device. When the embodiment is implemented in software, the techniques described in the present disclosure may be implemented in a module (e.g., process, function, etc.) for performing the function described in the present disclosure. A module may be stored in the memory  1010  and executed by the processor  1020 . The memory may be implemented inside of the processor  1020 . Alternatively, the memory  1010  may be implemented outside of the processor  1020  and may be connected to the processor  1020  in communicative connection through various means which is well-known in the art. 
     The transceiver  1031  is connected to the processor  1020  in a way to operate and transmits and/or receives a radio signal. The transceiver  1031  includes a transmitter and a receiver. The transceiver  1031  may include a baseband circuit to process a radio frequency signal. The transceiver controls one or more antennas to transmit and/or receive a radio signal. In order to initiate a communication, the processor  1020  transfers command information to the transceiver  1031  to transmit a radio signal that configures a voice communication data. The antenna functions to transmit and receive a radio signal. When receiving a radio signal, the transceiver  1031  may transfer a signal to be processed by the processor  1020  and transform a signal in baseband. The processed signal may be transformed into audible or readable information output through the speaker  1042 . 
     The speaker  1042  outputs a sound related result processed by the processor  1020 . The microphone  1052  receives a sound related input to be used by the processor  1020 . 
     A user inputs command information like a phone number by pushing (or touching) a button of the input unit  1053  or a voice activation using the microphone  1052 . The processor  1020  processes to perform a proper function such as receiving the command information, calling a call number, and the like. An operational data on driving may be extracted from the SIM card or the memory  1010 . Furthermore, the processor  1020  may display the command information or driving information on the display  1041  such that a user identifies it or for convenience. 
       FIG. 14  is a block diagram showing the configuration of the terminal shown in  FIG. 13  in more detail. 
     The terminal  100  may include a transceiver unit  1030 , a processor  1020 , a memory  1030 , a sensing unit  1060 , an output unit  1040 , an interface unit  1090 , an input unit  1050 , and a power supply unit  1080 , etc. Since the components shown in  FIG. 14  are not essential for implementing the terminal, the terminal described in this specification may have more or fewer components than those listed above. 
     More specifically, among the components, the transceiver  1030  include one or more modules that enable wireless communication between the terminal  100  and the wireless communication system, between the terminal  100  and another terminal  100 , or between the terminal  100  and an external server. In addition, the transceiver  1030  may include one or more modules for connecting the terminal  100  to one or more networks. 
     The transceiver  1030  may include at least one of a broadcast receiver  1032 , a mobile communication transceiver  1031 , a wireless Internet transceiver  1033 , a short-range communication unit  1034 , and a location information module  1150 . 
     The input unit  1050  includes a camera  1051  or an image input unit for inputting an image signal, a microphone  1052  or an audio input unit for inputting an audio signal, and a user input unit  1053  for receiving information from a user, for example, a touch key, a push key(mechanical key), etc. The voice data or image data collected by the input unit  1050  may be analyzed and processed as a user&#39;s control command. 
     The sensing unit  1060  may include one or more sensors for sensing at least one of information in the mobile terminal, surrounding environment information surrounding the mobile terminal, and user information. For example, the sensing unit  1060  may include a proximity sensor  1061 , an illumination sensor  1062 , an illumination sensor, a touch sensor, an acceleration sensor, a magnetic sensor, gravity Sensor (G-sensor), gyroscope sensor, motion sensor, RGB sensor, infrared sensor (IR sensor: infrared sensor), fingerprint sensor (finger scan sensor), ultrasonic sensor, optical sensors (eg, cameras (see  1051 )), microphones (see  1052 ), battery gauges, environmental sensors (eg, barometers, hygrometers, thermometers, radiation sensors, It may include at least one of a thermal sensor, a gas sensor, etc.) and a chemical sensor (eg, an electronic nose, a healthcare sensor, a biometric sensor, etc.). Meanwhile, the mobile terminal disclosed in the present specification may combine and utilize information sensed by at least two or more of these sensors. 
     The output unit  1040  is for generating an output related to visual, auditory or tactile sense, the output unit  1040  may include at least one of a display unit  1041 , a sound output unit  1042 , a haptip output unit  1043 , and an optical output unit  1044 . The display unit  1041  may implement a touch screen by forming a layer structure with the touch sensor each other or integrally formed with the touch sensor. Such a touch screen may function as a user input unit  1053  that provides an input interface between the terminal  100  and a user, and may provide an output interface between the terminal  100  and a user. 
     The interface unit  1090  serves as a passage with various types of external devices connected to the terminal  100 . This interface unit  1090  may include at least one of a wired/wireless headset port (port), an external charger port (port), a wired/wireless data port (port), a memory card (memory card) port, a port connecting a device equipped with an identification module, an audio input/output (I/O) port, a video input/output (I/O) port, and an earphone port. Corresponding to the connection of the external device to the interface unit  1090 , the terminal  100  may perform appropriate control related to the connected external device. 
     In addition, the memory  1030  stores data supporting various functions of the terminal  100 . The memory  1030  may store a plurality of application programs (or applications) driven in the terminal  100 , data for operation of the terminal  100 , and commands. At least some of these application programs may be downloaded from an external server through wireless communication. Also, at least some of these application programs may exist on the terminal  100  from the time of shipment for basic functions (eg, functions for incoming calls, outgoing functions, message reception, and message outgoing functions) of the terminal  100 . Meanwhile, the application program may be stored in the memory  1030 , installed on the terminal  100 , and driven by the processor  1020  to perform an operation (or function) of the mobile terminal. 
     The processor  1020  generally controls the overall operation of the terminal  100  in addition to the operation related to the application program. The processor  1020  may provide or process appropriate information or functions to a user by processing signals, data, information, etc. input or output through the above-described components or by driving an application program stored in the memory  1030 . 
     In addition, the processor  1020  may control at least some of the aforementioned components in order to drive an application program stored in the memory  1030 . Furthermore, the processor  1020  may operate by combining at least two or more of the components included in the terminal  100  to drive the application program. 
     The power supply unit  1080  receives external power and internal power under the control of the processor  1020  to supply power to each component included in the terminal  100 . The power supply unit  1080  includes a battery, and the battery may be a built-in battery or a replaceable battery. 
     At least some of the respective components may operate in cooperation with each other to implement an operation, control, or control method of a mobile terminal according to various embodiments to be described below. In addition, the operation, control, or control method of the mobile terminal may be implemented on the mobile terminal by driving at least one application program stored in the memory  1030 . 
     Hereinafter, before looking at various embodiments implemented through the terminal  100  as described above, the above-listed components will be described in more detail with reference to the drawings. 
     First, referring to the transceiver  1030 , the broadcast receiver  1032  of the transceiver  1030  receives a broadcast signal and/or broadcast related information from an external broadcast management server through a broadcast channel. The broadcast channel may include a satellite channel and a terrestrial channel. Two or more of the broadcast reception modules may be provided to the mobile terminal  100  for simultaneous broadcast reception or broadcast channel switching for at least two broadcast channels. 
     The mobile communication transceiver  1031  transmit and receive wireless signal with at least one of a base station, an external terminal, and a server on a mobile communication network constructed according to the technical standards or communication methods for mobile communication (eg, Global System for Mobile communication (GSM), Code Division Multi Access (CDMA), Code Division Multi Access 2000 (CDMA2000), Enhanced Voice-Data Optimized or Enhanced Voice-Data Only (EV-DO), Wideband CDMA (WCDMA), High Speed Downlink Packet Access (HSDPA), High Speed Uplink Packet Access (HSUPA), Long Term Evolution (LTE), LTE-A (Long Term Evolution-Advanced), 3GPP NR (New Radio access technology), etc.). 
     The wireless signal may include various types of data according to transmission and reception of a voice call signal, a video call signal, or a text/multimedia message. 
     The wireless Internet transceiver  1033  refers to a module for wireless Internet access, and may be built-in or external to the terminal  100 . The wireless Internet transceiver  1033  is configured to transmit and receive wireless signals in a communication network according to wireless Internet technologies. 
     As wireless Internet technologies, for example, WLAN (Wireless LAN), Wi-Fi (Wireless-Fidelity), Wi-Fi (Wireless Fidelity) Direct, DLNA (Digital Living Network Alliance), WiBro (Wireless Broadband), WiMAX (World Interoperability for Microwave Access), High Speed Downlink Packet Access (HSDPA), High Speed Uplink Packet Access (HSUPA), Long Term Evolution (LTE), Long Term Evolution-Advanced (LTE-A), 3GPP NR, and the like, and The Internet transceiver  1033  transmits and receives data according to at least one wireless Internet technology within a range including Internet technologies not listed above. 
     From the point of view that wireless Internet access by WiBro, HSDPA, HSUPA, GSM, CDMA, WCDMA, LTE, LTE-A, 3GPP NR, etc, is made through a mobile communication network, the wireless Internet transceiver  1033  performing wireless Internet access through the mobile communication network may be understood as a type of the mobile communication transceiver  1031 . 
     The short-range communication unit  1034  is for short-range communication, and may support short-distance communication by using at least one of Bluetooth™, Radio Frequency Identification (RFID), Infrared Data Association (IrDA), Ultra Wideband (UWB), ZigBee, NFC (Near Field Communication), Wi-Fi (Wireless-Fidelity), Wi-Fi Direct, and Wireless USB (Wireless Universal Serial Bus) technologies. The short-distance communication unit  1034  may support wireless communication between the terminal  100  and the wireless communication system, between the terminal  100  and the other terminal  100 , or between the terminal  100  and another network in which the other terminal ( 1000 , or external server) is located. The local area network may be wireless personal area networks. 
     Here, the other terminal  100  is a wearable device capable of exchanging (or interworking) data with the terminal  100  according to the present specification, for example, a smart watch, a smart glass, neckband, HMD (head mounted display). The short-range communication unit  1034  may detect (or recognize) a wearable device capable of communicating with the terminal  100  in the vicinity of the terminal  100 . Furthermore, when the detected wearable device is a device authenticated to communicate with the terminal  100  according to the present specification, the processor  1020  transmits at least a portion of data processed by the terminal  100  to a wearable device through the short-range communication unit  1034 . It can be transmitted. Accordingly, the user of the wearable device may use data processed by the terminal  100  through the wearable device. For example, according to this, when a call is received in the terminal  100 , it is possible for the user to perform a phone call through the wearable device, or when a message is received in the terminal  100 , it is possible for the user to receive the received message through the wearable device. 
     Furthermore, screen mirroring with a TV located in the house or a display inside a car is performed through the short-distance communication unit  1034 , and a corresponding function is performed based on, for example, the MirrorLink or Miracast standard. In addition, it is also possible to directly control a TV or a display inside a vehicle by using the terminal  100 . 
     The location information module  1150  is a module for acquiring a location (or current location) of a mobile terminal, and a representative example thereof includes a Global Positioning System (GPS) module or a Wireless Fidelity (WiFi) module. For example, if the mobile terminal utilizes a GPS module, it can acquire the location of the mobile terminal by using a signal transmitted from a GPS satellite. As another example, if the mobile terminal utilizes the Wi-Fi module, the location of the mobile terminal may be obtained based on information of the Wi-Fi module and a wireless access point (AP) that transmits or receives a wireless signal. If necessary, the location information module  1150  may perform any function of the other modules of the transceiver  1030  to obtain data on the location of the mobile terminal as a substitute or additionally. The location information module  1150  is a module used to obtain the location (or current location) of the mobile terminal, and is not limited to a module that directly calculates or obtains the location of the mobile terminal. 
     Each of the broadcast receiver  1032 , the mobile communication transceiver  1031 , the short-range communication unit  1034 , and the location information module  1150  may be implemented as a separate module performing a corresponding function, and functions corresponding to two or more of the transceiver  1031 , the short-range communication unit  1034 , and the location information module  1150  may be implemented by one module. 
     Next, the input unit  1050  is for inputting image information (or signal), audio information (or signal), data, or information input from a user, for input of image information, the terminal  100  may be provided with one or a plurality of cameras  1051 . The camera  1051  processes an image frame such as a still image or a moving image obtained by an image sensor in a video call mode or a photographing mode. The processed image frame may be displayed on the display unit  1041  or stored in the memory  1030 . On the other hand, the plurality of cameras  1051  provided in the terminal  100  may be arranged to form a matrix structure, and through the cameras  1051  forming the matrix structure as described above, image information may be input to the terminal  100  has a plurality of cameras having various angles or focal points. In addition, the plurality of cameras  1051  may be arranged in a stereo structure to acquire a left image and a right image for realizing a stereoscopic image. 
     The microphone  1052  processes an external sound signal as electrical voice data. The processed voice data may be utilized in various ways according to a function (or a running application program) being performed by the terminal  100 . Meanwhile, various noise removal algorithms for removing noise generated in the process of receiving an external sound signal may be implemented in the microphone  1052 . 
     The user input unit  1053  is for receiving information from a user, and when information is input through the user input unit  1053 , the processor  1020  may control the operation of the terminal  100  to correspond to the input information. The user input unit  1053  is a mechanical input means (or a mechanical key, for example, a button located on the front, rear or side of the terminal  100 , a dome switch, a jog wheel, a jog switch, etc.) and a touch input means. As an example, the touch input means consists of a virtual key, a soft key, or a visual key displayed on the touch screen through software processing, or consists of a touch key (touch key) disposed on a part other than the touch screen. On the other hand, the virtual key or the visual key, is possible to be displayed on the touch screen while having various forms, for example, graphic, text, icon, video or a combination of these forms. 
     Meanwhile, the sensing unit  1060  senses at least one of information in the mobile terminal, surrounding environment information surrounding the mobile terminal, and user information, and generates a sensing signal corresponding thereto. The processor  1020  may control the driving or operation of the terminal  100  or perform data processing, functions, or operations related to an application program installed in the terminal  100  based on the sensing signal. Representative sensors among various sensors that may be included in the sensing unit  1060  will be described in more detail. 
     First, the proximity sensor  1061  refers to a sensor that detects the presence or absence of an object approaching a predetermined detection surface or an object existing in the vicinity without mechanical contact using the force of an electromagnetic field or infrared rays. The proximity sensor  1061  may be disposed in an inner region of the mobile terminal covered by the touch screen described above or in the vicinity of the touch screen. 
     Examples of the proximity sensor  1061  include a transmission type photoelectric sensor, a direct reflection type photoelectric sensor, a mirror reflection type photoelectric sensor, a high frequency oscillation type proximity sensor, a capacitive type proximity sensor, a magnetic type proximity sensor, an infrared proximity sensor, and the like. In the case where the touch screen is capacitive, the proximity sensor  1061  may be configured to detect the proximity of an object having conductivity as a change in an electric field according to the proximity of the object. In this case, the touch screen (or touch sensor) itself may be classified as a proximity sensor. 
     On the other hand, for convenience of description, the act of approaching an object on the touch screen without being in contact so that the object is recognized that it is located on the touch screen is called “proximity touch”, and the act of actually touching an object on the screen is called “contact touch”. The position where the object is touched in proximity on the touch screen means a position where the object is perpendicular to the touch screen when the object is touched in proximity The proximity sensor  1061  may detect a proximity touch and a proximity touch pattern (eg, proximity touch distance, proximity touch direction, proximity touch speed, proximity touch time, proximity touch position, proximity touch movement state, etc.). On the other hand, the processor  1020  processes data (or information) corresponding to the proximity touch operation and the proximity touch pattern detected through the proximity sensor  1061  as above, and further, print visual information corresponding to the processed data on the touch screen. Furthermore, the processor  1020  may control the terminal  100  to process different operations or data (or information) according to whether a touch to the same point on the touch screen is a proximity touch or a contact touch. 
     The touch sensor detects a touch (or touch input) applied to the touch screen (or the display unit  1041 ) using at least one of various touch methods such as a resistive film method, a capacitive method, an infrared method, an ultrasonic method, and a magnetic field method, etc. 
     As an example, the touch sensor may be configured to convert a change in pressure applied to a specific part of the touch screen or a change in capacitance occurring in a specific part of the touch screen into an electrical input signal. The touch sensor may be configured to detect a position in which a touch object applying a touch on the touch screen, an area, a pressure at the time of touch, an electrostatic capacitance at the time of touch, etc. Here, the touch object is an object that applies a touch to the touch sensor, and may be, for example, a finger, a touch pen or a stylus pen, a pointer, or the like. 
     As such, when there is a touch input to the touch sensor, a signal(s) corresponding thereto is sent to the touch controller. The touch controller processes the signal(s) and then sends the corresponding data to the processor  1020 . Accordingly, the processor  1020  may know which area of the display unit  1041  has been touched, and the like. Here, the touch controller may be a component separate from the processor  1020 , or may be the processor  1020  itself. 
     Meanwhile, the processor  1020  may perform different controls or may perform the same control according to the type of the touch object that touches the touch screen (or a touch key provided other than the touch screen). Whether to perform different control or the same control according to the type of the touch object may be determined according to the current operating state of the terminal  100  or a running application program. 
     On the other hand, the touch sensor and the proximity sensor described above are independently or in combination, may sense various types of touch such as, a short (or tap) touch, a long touch, a multi touch, and a drag touch, flick touch, pinch-in touch, pinch-out touch, swype touch, hovering touch, etc. 
     The ultrasonic sensor may recognize location information of a sensing target by using ultrasonic waves. Meanwhile, the processor  1020  may calculate the position of the wave source based on information sensed by the optical sensor and the plurality of ultrasonic sensors. The position of the wave source may be calculated using the property that light is much faster than ultrasonic waves, that is, the time at which light reaches the optical sensor is much faster than the time at which ultrasonic waves reach the ultrasonic sensor. More specifically, the position of the wave source may be calculated by using a time difference from the time that the ultrasonic wave arrives using light as a reference signal. 
     On the other hand, the camera  1051  as described in terms of the components of the input unit  1050  includes at least one of a camera sensor (eg, CCD, CMOS, etc.), a photo sensor (or an image sensor), and a laser sensor. 
     The camera  1051  and the laser sensor may be combined with each other to detect a touch of a sensing target for a 3D stereoscopic image. The photo sensor may be stacked on the display device, and the photo sensor is configured to scan the motion of the sensing target close to the touch screen. More specifically, the photo sensor mounts photo diodes and transistors (TRs) in rows/columns and scans the contents placed on the photo sensors using electrical signals that change according to the amount of light applied to the photo diodes. That is, the photo sensor calculates the coordinates of the sensing target according to the amount of change in light, and through this, location information of the sensing target can be obtained. 
     The display unit  1041  displays (outputs) information processed by the terminal  100 . For example, the display unit  1041  may display execution screen information of an application program driven in the terminal  100  or UI (User Interface) and GUI (Graphic User Interface) information according to the execution screen information. 
     Also, the display unit  1041  may be configured as a stereoscopic display unit for displaying a stereoscopic image. 
     A three-dimensional display method such as a stereoscopic method (glasses method), an auto stereoscopic method (glasses-free method), or a projection method (holographic method) may be applied to the stereoscopic display unit. 
     The sound output unit  1042  may output audio data received from the transceiver  1030  or stored in the memory  1030  in a call signal reception, a call mode or a recording mode, a voice recognition mode, a broadcast reception mode, and the like. The sound output unit  1042  also outputs a sound signal related to a function (eg, a call signal reception sound, a message reception sound, etc.) performed in the terminal  100 . The sound output unit  1042  may include a receiver, a speaker, a buzzer, and the like. 
     The haptic module  1530  generates various tactile effects that the user can feel. A representative example of the tactile effect generated by the haptic output unit  1043  may be vibration. The intensity and pattern of vibration generated by the haptic output unit  1043  may be controlled by a user&#39;s selection or setting of a processor. For example, the haptic output unit  1043  may synthesize and output different vibrations or output them sequentially. 
     In addition to vibration, the haptic output unit  1043  may generate various tactile effects such as a pin arrangement that moves vertically with respect to the contact skin surface, a jet or suction force of air through a nozzle or an inlet, a touch on the skin surface, contact of an electrode, an electrostatic force, effect caused by heat absorption and the effect of reproducing a feeling of coolness and warmth using an element capable of absorbing heat or generating heat, etc. 
     The haptic output unit  1043  may not only deliver a tactile effect through direct contact, but may also be implemented so that the user can feel the tactile effect through a muscle sensation such as a finger or arm. Two or more haptic output units  1043  may be provided according to the configuration of the terminal  100 . 
     The light output unit  1044  outputs a signal for notifying the occurrence of an event by using the light of the light source of the terminal  100 . Examples of the event generated in the terminal  100  may be message reception, call signal reception, missed call, alarm, schedule notification, email reception, information reception through an application, and the like. 
     The signal output from the optical output unit  1044  is implemented as the mobile terminal emits light of a single color or a plurality of colors toward the front or rear side. The signal output may be terminated when the mobile terminal detects the user&#39;s event confirmation. 
     The interface unit  1090  serves as a passage with all external devices connected to the terminal  100 . The interface unit  1090  receives data from an external device, receives power and transmits it to each component inside the terminal  100 , or allows data inside the terminal  100  to be transmitted to an external device. For example, a wired/wireless headset port, an external charger port, a wired/wireless data port, a memory card port, a port for connecting a device equipped with an identification module (port), an audio I/O (Input/Output) port, a video I/O (Input/Output) port, an earphone port, etc. may be included in the interface unit  1090 . 
     On the other hand, the identification module is a chip storing various information for authenticating the use authority of the terminal  100 , the identification module may include a user identification module (UIM), a subscriber identity module (subscriber identity module; SIM), a universal user authentication module (universal subscriber identity module; USIM) and the like. A device equipped with an identification module (hereinafter, ‘identification device’) may be manufactured in the form of a smart card. Accordingly, the identification device may be connected to the terminal  100  through the interface unit  1090 . 
     In addition, the interface unit  1090  may be a path through which power from the cradle is supplied to the terminal  100  when the terminal  100  is connected to an external cradle, or a path through which various commands signal input from the cradle by the user transmitted to the terminal  100 . Various command signals or the power input from the cradle may be operated as signals for recognizing that the terminal  100  is correctly mounted on the cradle. 
     The memory  1030  may store a program for the operation of the processor  1020 , and may temporarily store input/output data (eg, a phone book, a message, a still image, a moving image, etc.). The memory  1030  may store data related to vibrations and sounds of various patterns output when a touch input is performed on the touch screen. 
     The memory  1030  may include at least one type of storage medium such as a flash memory type, a hard disk type, a solid state disk type (SSD), a silicon disk drive type (SDD), and a multimedia card micro type.), card-type memory (such as SD or XD memory), random access memory (RAM), static random access memory (SRAM), read-only memory (ROM), electrically erasable programmable read-only memory (EEPROM), a programmable read-only memory (PROM), a magnetic memory, a magnetic disk, and an optical disk. The terminal  100  may be operated in relation to a web storage that performs a storage function of the memory  1030  on the Internet. 
     Meanwhile, as described above, the processor  1020  controls the operation related to the application program and the general operation of the terminal  100  in general. For example, if the state of the mobile terminal satisfies a set condition, the processor  1020  may execute or release a lock state that restricts input of a user&#39;s control command to applications. 
     In addition, the processor  1020  may perform control and processing related to voice calls, data communication, video calls, etc., or perform pattern recognition processing capable of recognizing handwriting input or drawing input performed on the touch screen as text and images, respectively. Furthermore, the processor  1020  may control any one or a plurality of the components described above in combination to implement various embodiments described below on the terminal  100  according to the present specification. 
     The power supply unit  1080  receives external power and internal power under the control of the processor  1020  to supply power necessary for operation of each component. The power supply unit  1080  includes a battery, and the battery may be a built-in battery configured to be rechargeable, and may be detachably coupled to the terminal body for charging or the like. 
     In addition, the power supply unit  1080  may include a connection port, and the connection port may be configured as an example of the interface  1090  to which an external charger that supplies power for charging the battery is electrically connected. 
     As another example, the power supply unit  1080  may be configured to charge the battery in a wireless manner without using the connection port. In this case, power can be transmitted to the power supply unit  1080  uses one or more of an inductive coupling method based on a magnetic induction phenomenon or a resonance coupling method based on an electromagnetic resonance phenomenon from an external wireless power transmitter. 
     Meanwhile, various embodiments below may be implemented in, for example, a computer-readable recording medium using software, hardware, or a combination thereof. 
     On the other hand, the mobile terminal can be extended to a wearable device that can be worn on the body beyond the dimension that the user mainly holds in the hand. Such wearable devices include a smart watch, smart glass, and head mounted display (HMD) and the like. Hereinafter, examples of mobile terminals extended to wearable devices will be described. 
     The wearable device may be configured to be able to exchange (or interwork) data with another terminal  100 . The short-range communication unit  1034  may detect (or recognize) a wearable device capable of communicating around the terminal  100 . Furthermore, when the detected wearable device is a device authenticated to communicate with the terminal  100 , the processor  1020  may transmit at least a portion of data processed in the terminal  100  to the wearable device through the short-range communication unit  1034 . Accordingly, the user may use data processed by the terminal  100  through the wearable device. For example, it is possible to perform a phone call through the wearable device when a call is received in the terminal  100 , or to check the received message through the wearable device when a message is received to the terminal  100 . 
     Hereinafter, an embodiment based on EPS and 5GS (5G System) will be described, but the content disclosed by this specification is also applicable to an embodiment implemented in 5GS. 
     In this specification, a special roaming situation mode of the terminal is defined. (ie, not a normal roaming situation, but a roaming situation that operates to overcome the failure situation as described above). To facilitate the description herein, general roaming is referred to as N-roaming, and roaming that operates to overcome the failure situation is referred to as S-roaming (Special roaming) or E-roaming (Emergency roaming). Hereinafter, the disclosure of the present specification will be described focusing on S-roaming, and the description of S-roaming may be equally applied to E-roaming. 
     As described in the above problem, if the terminal does not understand the S-roaming (ie, roaming operated to overcome a failure situation. Hereinafter also referred to as disaster roaming or emergency roaming), the terminal recognizes it as a non-roaming situation and operates. If the terminal recognizes the S-roaming situation through the contents described in the disclosure of this specification, the terminal may operate in the S-roaming mode preset by the operator. The terminal may recognize that it is operating in the S-roaming mode. 
     The operator&#39;s settings may be pre-configured or transmitted to the terminal through an Open Mobile Alliance (OMA)-DM (Device Management) method or a policy transmission method. The setting of the operator may be updated as necessary. 
     For example, the operator (eg, the first operator of the first PLMN) allows the request for voice and SMS of the inbound roaming terminal (the terminal subscribed to the second PLMN) in the S-roaming situation, but the operator (eg, the first operator of the first PLMN) may set data Service requests be limited. In addition, the operator may set the priority of random access by a specific application of the inbound roaming terminal differently from the general situation. Alternatively, for the purpose of adjusting the signal load, the operator may change the period of the P-TAU (periodic tracking area update) of the terminal, or may set the non-essential request during the operation of the terminal to be delayed. 
     For reference, a failure occurring in the second PLMN may be referred to as a communication disaster. A disaster is damage to human life or property due to a change in natural phenomena such as weather or man-made accidents. A telecommunication disaster means a failure of a specific telecommunication company caused by a disaster. In the present specification, disaster (or communication disaster) and failure (or network failure) are used as words having the same meaning. 
     When a failure occurs in the second PLMN of the disaster operator (ie, the second operator), the first PLMN of the roaming operator (ie, the first operator) may accommodate the subscribers of the disaster operator. In this case, the roaming service provider may selectively accommodate subscribers of the disaster service provider using a specific frequency band. Here, the specific frequency band may be a frequency band used in the second PLMN of the disaster operator. 
     For example, the base station in the first PLMN of the roaming operator may broadcast the roaming operator PLMN identifier (the first PLMN identifier) and the disaster operator PLMN identifier (the second PLMN identifier) together using the SIB message in a specific frequency band. For reference, the first operator may provide information related to the failure occurring in the second PLMN of the second operator to the base station in the first PLMN. For example, the first operator may notify the base station in the first PLMN of information related to a failure occurring in the second PLMN by an OAM (Operations, Administration and Maintenance) method. In addition, the base station in the first PLMN may broadcast only the roaming operator PLMN identifier in a frequency band other than a specific frequency band. Then, the subscriber terminal of the disaster service provider may be provided with a communication service through the base station in the first PLMN by tuning to a specific frequency band of the base station in the first PLMN through cell search. 
       FIGS. 15 and 16  are examples of a network structure in which a subscriber of the second PLMN having a failure is provided with a service through a base station in the first PLMN according to the disclosure of the present specification. 
     In  FIGS. 15 and 16 , EIR is an Equipment Identity Register. The EIR may be a database that manages the identity information of the terminal. The identity information may be, for example, International Mobile Equipment Identity (IMEI). 
     HLR is the Home Location Register. The HLR may be a database storing information of users who have subscribed to a mobile communication network (a first PLMN or a second PLMN). User information is stored in the SIM and transmitted to the mobile communication network through the network, and the HLR may store and manage data for authenticating the transmitted information. For example, the HLR may store and manage a key value required for authentication, including an International Mobile Subscriber Identity (IMSI), which is a unique identification number for a user. 
     AuC is the Authentication Center. AuC can authenticate the user by using the key value for user authentication stored in the HLR. The AuC may determine whether the user is a suitable user who can use the corresponding mobile communication network. 
     GLR is the Gateway Location Register. The GLR may serve as a gateway when exchanging information of a roaming terminal between a home network (eg, a second PLMN) and a visited network (eg, a first PLMN) when the terminal roams. The information of the roaming terminal may be, for example, subscriber location information or a profile. 
     For reference, in  FIGS. 13 to 22 , PLMN  1  (eg, a PLMN of a telecommunication operator SKT (SK Telecom, Korea)) means a first PLMN. The first PLMN may be a PLMN that provides a disaster roaming service. PLMN  2  (eg, PLMN of telecommunication operator KT (KT corporation in Korea)) means the second PLMN. The second PLMN is a PLMN in which a network failure (communication disaster) has occurred. 
       FIGS. 15 and 16  assume that a failure (disaster) occurs in the second PLMN (PLMN  2 ). When a failure occurs in the second PLMN, the base station of the first PLMN (PLMN  1 ) may broadcast the SIB message including information on the second PLMN. Then, the terminal subscribed to the second PLMN may be provided with a service through the base station in the first PLMN. 
       FIG. 15  shows an example of an EPS network structure related to the disclosure of the present specification. 
     Referring to  FIG. 15 , when a failure occurs in a base station (eNB) in the second PLMN, a terminal subscribed to the second PLMN cannot receive a service through the base station in the second PLMN. When the first PLMN recognizes that a failure has occurred in the second PLMN, the base station (eNB) in the first PLMN may broadcast the SIB message including information on the second PLMN. Then, the terminal subscribed to the second PLMN (the second operator subscription terminal) may be provided with a service through the base station in the first PLMN. 
     For example, the MME in the first PLMN communicates with the GLR and HLR/AuC/EIR in the second PLMN through the GLR in the first PLMN to authenticate the UE subscribed to the second PLMN, and may determine whether to allow disaster roaming (S-roaming) or not. If the MME allows disaster roaming (S-roaming) of the terminal subscribed to the second PLMN, the terminal subscribed to the second PLMN may establish service connection with P-GW, IMS, GLR and Internet in the second PLMN through the base station, S-GW, MME and GLR in the first PLMN. 
       FIG. 16  shows an example of an 5GS network structure related to the disclosure of the present specification. 
     Referring to  FIG. 16 , when a failure occurs in a base station (gNB) in the second PLMN, a terminal subscribed to the second PLMN cannot receive a service through the base station in the second PLMN. When the first PLMN recognizes that a failure has occurred in the second PLMN, the base station (gNB) in the first PLMN may broadcast the SIB message including information on the second PLMN. Then, the terminal subscribed to the second PLMN (the second operator subscription terminal) may be provided with a service through the base station in the first PLMN. 
     For example, the AMF in the first PLMN communicates with the GLR and UDM/AuC/EIR in the second PLMN through the GLR in the first PLMN to authenticate the terminal subscribed to the second PLMN, and may determine whether to allow disaster roaming (S-roaming) or not. If the AMF allows disaster roaming (S-roaming) of the terminal subscribed to the second PLMN, the terminal subscribed to the second PLMN may establish service connection with SMF, AMF, IMS and the Internet in the second PLMN through a base station AMF, SMF, UPF, UPF, and GLR in the first PLMN. 
     I. Method to Handle Network Failure Situation 
     As described in the examples of  FIGS. 15 and 16 , even if a failure occurs in the second PLMN, the terminal subscribed to the second PLMN may receive a service through the base station of the first PLMN based on S-roaming An example of a method for allowing the terminal to recognize the S-roaming situation will be described. 
     For what will be described below assumes a situation that a network failure (ie, a communication disaster) occurs in the second PLMN (eg, the network of the telecommunication service provider KT), and the terminal subscribed to the second PLMN cannot be provided with the communication service through the base station in the second PLMN. In addition, situation is assumed that the base station in the first PLMN (eg, the network of the telecommunication operator SKT) transmits the SIB message by including the second PLMN information in the SIB message, based on a preset policy or operator command (OAM (Operation and Maintenance) command) for a specific time (eg, time until the failure of the second PLMN to be resolved). 
     The terminal recognizing the S-roaming situation based on at least one of the first to third examples to be described later, transmits a message (eg, various types of messages such as an access request message) to the network by including information indicating that the terminal has been recognized the S-roaming situation in the message. 
     This message (including information indicating that the terminal has recognized the S-roaming situation) may be used for the purpose of helping control and management in the network. For example, such a message may be used to prevent signaling waste by preventing the network from continuously sending the same information (eg, information indicating an S-roaming situation) to the corresponding terminal. In addition, this message may be used for the purpose of causing the network to perform a specific operation for terminals recognizing the S-roaming situation. 
     For reference, the UE of  FIGS. 17 to 22  means a UE subscribed to the second PLMN. The term “terminal” used in the description of  FIGS. 17 to 22  refers to a terminal subscribed to the second PLMN. 
     For reference, the first to third examples are described below with reference to the drawings, respectively, but the operations of the first to third examples may be implemented alone, or the operations of the first to third examples may be implemented in combination. 
     I-1. Example Based on AS Layer Signaling (1st Example) 
     When a failure occurs in the second PLMN by the second operator, the base station in the first PLMN broadcasts an SIB message by including including PLMN information of the third party (other company) (second PLMN information) in order to provide a service to a terminal subscribed to the second PLMN in the disabled area (hereinafter also referred to as a second PLMN terminal). In this case, the base station in the first PLMN may transmit SIB message including information notifying the second PLMN terminal that the condition due to the failure or the S-roaming condition. The base station in the first PLMN may transmit information indicating that the condition due to a failure or the S-roaming condition by including the information in a specific prefix. For example, the base station in the first PLMN may include a pre-configured specific value or a pre-defined specific value in order to inform that it is an S-roaming situation in a specific field of the SIB message. 
     In the case of a terminal that does not support the operation based on S-roaming, even if the first PLMN base station transmits information indicating that the S-roaming situation is S-roaming, the terminal may not recognize the S-roaming situation. Such a terminal operates by determining that it has accessed the second PLMN. 
     In the case of a terminal supporting an operation based on S-roaming, after receiving the SIB message from the base station in the first PLMN, the terminal may use information included in the SIB message when the terminal attempts to access a specific base station among multiple base stations. For example, the terminal may use information indicating the S-roaming situation as one of the elements used when attempting to access by selecting a base station in the first PLMN among information received from multiple base stations. If the terminal needs to access the network based on the S-roaming situation due to a failure occurring in the second PLMN, the terminal may attempt to access the network through the base station in the first PLMN. In this case, the terminal may switch the operation mode of the terminal to the S-roaming mode or apply an S-roaming policy to perform a network access and a request with respect to the network. 
     When the terminal receives the SIB message indicating that the S-roaming situation is present or when network access is permitted, the terminal may switch the operation mode to the S-roaming mode or apply the S-roaming policy. Specifically, the time when the terminal switches the operation mode to the S-roaming mode or applies the S-roaming policy may be the time when the SIB message indicating that the S-roaming situation is received or after successful connection with the network is completed. For example, after receiving the acceptance message for the access request from the network, the terminal may switch the operation mode to the S-roaming mode or apply the S-roaming policy. 
     A situation in which a mobile communication service can no longer be provided through the corresponding base station is described. Temporarily (for example, hours or days, etc.) until the physical recovery of the corresponding base station is made, it is assumed that situation that the base station of the first PLMN by the first operator broadcasts the SIB message includes information on the second PLMN by a third party (other company) (ie, the second operator) in order to provide a service on behalf of the second operator in the affected area. 
     The first example may be performed in various communication systems. For example, the first example may be performed in EPC or 5GS. In addition, the first example may be performed between the EPC of the first operator and the 5GS of the second operator, or may be performed between the 5GS of the first operator and the EPC of the second operator. The description of  FIGS. 17A and 17B  and the description of  FIGS. 18A and 18B  to be described later are only examples, and the scope of the present specification is not limited to the description of  FIGS. 17A and 17B  and the description of  FIGS. 18A and 18B . 
       FIGS. 17A and 17B  show an embodiment in which a first example of the disclosure of the present specification is applied to an EPS. 
     0) The terminal may configure the disaster roaming mode by user interaction or operator configuration. Specifically, when the terminal receives disaster roaming information from the network later, the terminal can be configured whether to operate in the disaster roaming mode or not by user interaction or operator configuration. For example, the disaster roaming mode setting of step 0) is a setting for whether to operate in the disaster roaming mode when a disaster roaming message is received from the network later, and is independent of whether the terminal supports the disaster roaming function, that is, it means that even a terminal supporting a roaming function may perform a different operation (eg, not operating in a disaster roaming mode) according to the settings of the user or operator. 
     1) The base station in the first PLMN may broadcast the information of the second PLMN by temporarily including the information of the second PLMN in the SIB message based on at least one of a preset policy or an operator command (OAM command) Upon receiving the SIB message including the information of the second PLMN, the terminal may recognize the base station in the first PLMN as the base station of the second PLMN and perform an operation of attempting to access the second PLMN. The SIB message may additionally include, directly or indirectly, information indicating a disaster roaming (network failure) situation. Here, the base station in the first PLMN may transmit the information of the second PLMN or information indicating the disaster roaming situation in the form of an AS message, that is, included in the SIB message. 
     2) The AS layer of the terminal may recognize at least one of information of the second PLMN included in the SIB message or information indicating a disaster roaming situation. 
     When the SIB message includes information notifying a disaster roaming situation, and the AS layer of the terminal recognizes this information, the AS layer of the terminal directly or indirectly provide information indicating the disaster roaming situation through the terminal&#39;s internal interface to the NAS layer of the terminal. The NAS layer of the terminal may perform at least one of an operation of switching the operation mode of the terminal to a disaster roaming mode or an operation of applying a preset disaster roaming policy based on information indicating the disaster roaming situation. 
     If the SIB message does not include information indicating a disaster roaming situation, but only includes the information of the second PLMN, the AS layer of the terminal cannot recognize the information indicating the disaster roaming situation, so the NAS layer of the terminal does not perform operation switching to the disaster roaming mode or operation applying the roaming policy. 
     3) The terminal may transmit an access request message to attempt access to the second PLMN. Here, the access request message may be an attach request message. The access request message transmitted by the terminal is physically transmitted to the MME in the first PLMN through the base station in the first PLMN. 
     4) The MME in the first PLMN may determine whether to allow disaster roaming The MME may perform an interaction with the HSS in the second PLMN to check subscriber information of the terminal that has transmitted the access request message. The MME may check a set operator policy or a preset operator policy and preset roaming policy. If necessary, the MME may perform interconnection with other network nodes, such as PCRF, to check the operator policy. 
     Through this process, the MME may determine whether or not to allow disaster roaming of the terminal that has transmitted the access request message (eg, whether to accept access to provide disaster roaming service to the terminal) and may determine the scope of the disaster roaming service if disaster roaming is allowed. Here, the scope of the disaster roaming service may be, for example, a basic voice call and a specific service. 
     According to the determination result of the MME in the first PLMN, the case A operation or the case B operation may be performed. 
     Case A: When the MME allows disaster roaming of the terminal (when the access request of the terminal is accepted) 
     5A) The MME in the first PLMN may process the access request of the terminal and perform a procedure for configuring (establishing) a PDN connection for service provision. The MME in the first PLMN may exchange create session request/response messages with the P-GW in the second PLMN via the S-GW in the first PLMN. 
     6A) After the MME in the first PLMN successfully configures (establishes) the PDN connection, it may transmit an access acceptance message to the terminal. The connection accept message may be an attach accept message. The access acceptance message may include information on disaster roaming directly or implicitly. 
     Upon receiving the access acceptance message, the terminal may display information on disaster roaming to the user. For example, the terminal may display information on disaster roaming on the display unit of the terminal in a form or method recognizable by the user. Alternatively, the terminal may inform the user of information on disaster roaming using vibration or sound. 
     7A) The terminal may switch the operation mode to the disaster roaming mode based on information on disaster roaming included in the access acceptance message. The terminal may start applying a preset disaster roaming policy based on information on disaster roaming For reference, the disaster roaming mode switching and application of the disaster roaming policy may be performed in step 2) described above, but may also be performed in step 7A) after the terminal receives the access acceptance message. 
     8A) The terminal may transmit IMS signaling to the IMS network (eg, P-CSCF) in the second PLMN through the PDN connection configured (established) in step 6A). Then, the terminal may be provided with an IMS-related service such as a voice service through IMS signaling. Specifically, the IMS signaling of the terminal may be transmitted to the IMS network in the second PLMN via the S-GW in the first PLMN and the P-GW in the second PLMN. In other words, the UE may perform IMS signaling with the IMS network in the second PLMN. 
     Case B: When the MME does not allow disaster roaming of the terminal (when the access request of the terminal is rejected) 
     5B) The MME in the first PLMN may transmit an access rejection message to the terminal. The connection rejection message may be an attach rejection message. The access rejection message may directly or implicitly include information on disaster roaming. 
     6B) After receiving the access rejection message, the terminal evaluates the reason for rejection of the access rejection message, and then may perform PLMN re-selection. The UE may manage the priority of the PLMN based on the information on disaster roaming For example, the terminal may perform a control operation such as temporarily lowering the priority of the second PLMN in which disaster roaming has occurred or for a specific time. 
       FIGS. 18A and 18B  show an embodiment in which the first example of the disclosure of the present specification is applied to 5GS. 
     0) The terminal may configure the disaster roaming mode by user interaction or operator configuration. Specifically, when the terminal receives disaster roaming information from the network later, the terminal can be configured whether to operate in the disaster roaming mode or not by user interaction or operator configuration. For example, the disaster roaming mode setting of step 0) is a setting for whether to operate in the disaster roaming mode when a disaster roaming message is received from the network later, and is independent of whether the terminal supports the disaster roaming function, that is, it means that even a terminal supporting a roaming function may perform a different operation (eg, not operating in a disaster roaming mode) according to the settings of the user or operator. 
     1) The base station in the first PLMN may broadcast the information of the second PLMN by temporarily including the information of the second PLMN in the SIB message based on at least one of a preset policy or an operator command (OAM command) Upon receiving the SIB message including the information of the second PLMN, the terminal may recognize the base station in the first PLMN as the base station of the second PLMN and perform an operation of attempting to access the second PLMN. The SIB message may additionally include, directly or indirectly, information indicating a disaster roaming (network failure) situation. Here, the base station in the first PLMN may transmit the information of the second PLMN or information indicating the disaster roaming situation in the form of an AS message, that is, included in the SIB message. 
     2) The AS layer of the terminal may recognize at least one of information of the second PLMN included in the SIB message or information indicating a disaster roaming situation. 
     When the SIB message includes information notifying a disaster roaming situation, and the AS layer of the terminal recognizes this information, the AS layer of the terminal directly or indirectly provide information indicating the disaster roaming situation through the terminal&#39;s internal interface to the NAS layer of the terminal. The NAS layer of the terminal may perform at least one of an operation of switching the operation mode of the terminal to a disaster roaming mode or an operation of applying a preset disaster roaming policy based on information indicating the disaster roaming situation. 
     If the SIB message does not include information indicating a disaster roaming situation, but only includes the information of the second PLMN, the AS layer of the terminal cannot recognize the information indicating the disaster roaming situation, so the NAS layer of the terminal does not perform operation switching to the disaster roaming mode or operation applying the roaming policy. 
     3) The terminal may transmit an access request message to attempt access to the second PLMN. Here, the access request message may be an registration request message. The access request message transmitted by the terminal is physically transmitted to the AMF in the first PLMN through the base station in the first PLMN. 
     4) The AMF in the first PLMN may determine whether to allow disaster roaming The AMF may perform an interaction with the UDM in the second PLMN to check subscriber information of the terminal that has transmitted the access request message. The AMF may check a set operator policy or a preset operator policy and preset roaming policy. If necessary, the AMF may perform interconnection with other network nodes, such as PCF, to check the operator policy. 
     Through this process, the AMF may determine whether or not to allow disaster roaming of the terminal that has transmitted the access request message (eg, whether to accept access to provide disaster roaming service to the terminal) and may determine the scope of the disaster roaming service if disaster roaming is allowed. Here, the scope of the disaster roaming service may be, for example, a basic voice call and a specific service. 
     According to the determination result of the AMF in the first PLMN, the case A operation or the case B operation may be performed. 
     Case A: When the AMF allows disaster roaming of the terminal (when the access request of the terminal is accepted) 
     5A) The AMF in the first PLMN may transmit an access acceptance message to the terminal. The connection accept message may be a registration accept message. The access acceptance message may include information on disaster roaming directly or implicitly. 
     Upon receiving the access acceptance message, the terminal may display information on disaster roaming to the user. For example, the terminal may display information on disaster roaming on the display unit of the terminal in a form or method recognizable by the user. Alternatively, the terminal may inform the user of information on disaster roaming using vibration or sound. 
     6A) The terminal may switch the operation mode to the disaster roaming mode based on information on disaster roaming included in the access acceptance message. The terminal may start applying a preset disaster roaming policy based on information on disaster roaming For reference, the disaster roaming mode switching and application of the disaster roaming policy may be performed in step 2) described above, but may also be performed in step 6A) after the terminal receives the access acceptance message. 
     7A) The terminal may transmit the PDU session establishment request message to the SMF in the second PLMN via the base station and the AMF in the first PLMN. 
     The difference from the embodiment applied to the EPS described in  FIGS. 17A and 17B  is that in the embodiment applied to the 5GS, the SMF in the second PLMN may perform additional disaster roaming evaluation. For example, the SMF in the second PLMN may allow the disaster roaming service only for a specific PDU session among PDU sessions. In other words, the SMF in the second PLMN may determine the range of the emergency roaming service of the terminal. 
     The AMF in the first PLMN may communicate with the SMF (intermediate SMF (I-SMF) in  FIGS. 18A and 18B ) in the first PLMN, and the SMF in the first PLMN may communicate with the SMF in the second PLMN. That is, the SMF in the first PLMN may transmit and receive messages for communicating with the SMF in the second PLMN. The SMF in the first PLMN may perform the role of the I-SMF. 
     Alternatively, unlike shown, according to the disaster roaming deployment option, the AMF in the first PLMN may perform direct communication with the SMF in the second PLMN, which is the home PLMN of the terminal, and may transmit and receive messages with the SMF in the second PLMN. 
     Upon receiving the PDU session establishment request message, the SMF in the second PLMN may transmit the PDU session establishment response message to the terminal through the AMF of the first PLMN and the base station in the first PLMN. 
     8A) The UE may transmit IMS signaling to the IMS network (eg, PCF) in the second PLMN through the PDU session configured (established) in step 7A). Then, the terminal may be provided with an IMS-related service such as a voice service through IMS signaling. Specifically, the IMS signaling of the terminal may be transmitted to the IMS network in the second PLMN through the base station in the first PLMN, the UPF in the first PLMN (not shown in  FIGS. 18A and 18B ), and the UPF in the second PLMN. In other words, the UE may perform IMS signaling with the IMS network in the second PLMN. 
     Case B: When the AMF does not allow disaster roaming of the terminal (when the access request of the terminal is rejected) 
     5B) The AMF in the first PLMN may transmit an access rejection message to the terminal. The connection rejection message may be an attach rejection message. The access rejection message may directly or implicitly include information on disaster roaming 
     6B) After receiving the access rejection message, the terminal evaluates the reason for rejection of the access rejection message, and then may perform PLMN re-selection. The UE may manage the priority of the PLMN based on the information on disaster roaming. For example, the terminal may perform a control operation such as temporarily lowering the priority of the second PLMN in which disaster roaming has occurred or for a specific time. 
     I-2. Example Based on NAS Layer Signaling (2nd Example) 
     When a failure occurs in the second PLMN by the second operator, the base station in the first PLMN may broadcast an SIB message by including PLMN information of a third party (other company) (second PLMN information) in order to provide a service to a terminal (hereinafter also referred to as a second PLMN terminal) subscribed to the second PLMN in the disabled area. 
     When the terminal transmits an access request message to the network, the terminal does not recognize that a disaster roaming situation will proceed. The terminal transmits a general access request message to the base station in the first PLMN. That is, the terminal transmits the access request message to the base station in the first PLMN in the same manner as the method of transmitting the access request message to the second PLMN to which it is subscribed. 
     A network node (eg, MME or AMF) in the first PLMN may transmit an access acceptance message to the terminal based on information of the terminal, subscriber information, roaming agreement (eg, agreement on network failure situation) information, and the like. In this case, the network node in the first PLMN may inform the terminal of the S-roaming situation through a NAS message. 
     In the case of a terminal that does not support the operation based on S-roaming, even if the first PLMN base station transmits information indicating the S-roaming situation, the terminal may not recognize the S-roaming situation. Such a terminal operates by determining that it has accessed the second PLMN. 
     In the case of a terminal supporting an operation based on S-roaming, after receiving the SIB message from the base station in the first PLMN, the terminal may use information included in the SIB message when the terminal attempts to access a specific base station among multiple base stations. For example, the terminal may use information indicating the S-roaming situation as one of the elements used when attempting to access by selecting a base station in the first PLMN among information received from multiple base stations. If the terminal needs to access the network based on the S-roaming situation due to a failure occurring in the second PLMN, the terminal may attempt to access the network through the base station in the first PLMN. In this case, the terminal may switch the operation mode of the terminal to the S-roaming mode or apply an S-roaming policy to perform a network access and a request with respect to the network. 
     Additionally, the terminal may operate in the S-roaming mode or the terminal may apply the S-roaming policy only in a situation in which the terminal is connected to the base station of the first PLMN through the interaction between the AS layer and the NAS layer of the terminal. For example, when the network node recognizes that the base station to which the terminal is connected has changed while the terminal is connected to the network, the network node may review again whether the current terminal situation is the S-roaming situation. And, the network node may transmit the review result to the terminal as a NAS message. 
     For example, the terminal may move out of the failure area, and the base station to which the terminal is connected may be changed to a base station in the second PLMN, and the terminal may be connected to the second PLMN core network. Then, the network node (eg, MME or AMF, etc.) of the second PLMN can recognize that there was the S-roaming situation by checking the context of the terminal according to the conventional procedure, and transmit Information indicating that S-roaming it has been released to the terminal as a NAS message. 
     The second example may be performed in various communication systems. For example, the second example may be performed in EPC or 5GS. In addition, the second example may be performed between the EPC of the first operator and the 5GS of the second operator, or may be performed between the 5GS of the first operator and the EPC of the second operator. The description of  FIGS. 19A and 19B  and the description of  FIGS. 20A and 20B , which will be described later, are only examples, and the scope of the present specification is not limited to the description of  FIGS. 19A and 19B  and the description of  FIGS. 20A and 20B . 
       FIGS. 19A and 19B  show an embodiment in which a second example of the disclosure of the present specification is applied to an EPS. 
     0) The terminal may configure the disaster roaming mode by user interaction or operator configuration. Specifically, when the terminal receives disaster roaming information from the network later, the terminal can be configured whether to operate in the disaster roaming mode or not by user interaction or operator configuration. For example, the disaster roaming mode setting of step 0) is a setting for whether to operate in the disaster roaming mode when a disaster roaming message is received from the network later, and is independent of whether the terminal supports the disaster roaming function, that is, it means that even a terminal supporting a roaming function may perform a different operation (eg, not operating in a disaster roaming mode) according to the settings of the user or operator. 
     1) The base station in the first PLMN may broadcast the information of the second PLMN by temporarily including the information of the second PLMN in the SIB message based on at least one of a preset policy or an operator command (OAM command) Upon receiving the SIB message including the information of the second PLMN, the terminal may recognize the base station in the first PLMN as the base station of the second PLMN and perform an operation of attempting to access the second PLMN. The SIB message may additionally include, directly or indirectly, information indicating a disaster roaming (network failure) situation. 
     2) The terminal may transmit an access request message to attempt access to the second PLMN. Here, the access request message may be an attach request message. The access request message transmitted by the terminal is physically transmitted to the MME in the first PLMN through the base station in the first PLMN. 
     3) The MME in the first PLMN may determine whether to allow disaster roaming The MME may perform an interaction with the HSS in the second PLMN to check subscriber information of the terminal that has transmitted the access request message. The MME may check a set operator policy or a preset operator policy and preset roaming policy. If necessary, the MME may perform interconnection with other network nodes, such as PCRF, to check the operator policy. 
     Through this process, the MME may determine whether or not to allow disaster roaming of the terminal that has transmitted the access request message (eg, whether to accept access to provide disaster roaming service to the terminal) and may determine the scope of the disaster roaming service if disaster roaming is allowed. Here, the scope of the disaster roaming service may be, for example, a basic voice call and a specific service. 
     According to the determination result of the MME in the first PLMN, the case A operation or the case B operation may be performed. 
     Case A: When the MME allows disaster roaming of the terminal (when the access request of the terminal is accepted) 
     4A) The MME in the first PLMN may process the access request of the terminal and perform a procedure for configuring (establishing) a PDN connection for service provision. The MME in the first PLMN may exchange create session request/response messages with the P-GW in the second PLMN via the S-GW in the first PLMN. 
     5A) After the MME in the first PLMN successfully configures (establishes) the PDN connection, it may transmit an access acceptance message to the terminal. The connection accept message may be an attach accept message. The access acceptance message may include information on disaster roaming directly or implicitly. Here, information on disaster roaming may be included in the access acceptance message in the form of a NAS message. 
     Upon receiving the access acceptance message, the terminal may display information on disaster roaming to the user. For example, the terminal may display information on disaster roaming on the display unit of the terminal in a form or method recognizable by the user. Alternatively, the terminal may inform the user of information on disaster roaming using vibration or sound. 
     6A) The terminal may switch the operation mode to the disaster roaming mode based on information on disaster roaming included in the access acceptance message. The terminal may start applying a preset disaster roaming policy based on information on disaster roaming. 
     7A) The terminal may transmit IMS signaling to the IMS network (eg, P-CSCF) in the second PLMN through the PDN connection configured (established) in step 5A). Then, the terminal may be provided with an IMS-related service such as a voice service through IMS signaling. Specifically, the IMS signaling of the terminal may be transmitted to the IMS network in the second PLMN via the S-GW in the first PLMN and the P-GW in the second PLMN. In other words, the UE may perform IMS signaling with the IMS network in the second PLMN. 
     8A) If the network node (eg, MME) detects that the base station to which the terminal is connected is changed while the terminal is receiving a service based on disaster roaming, the MME may perform disaster roaming evaluation again. For example, if the base station to which the terminal is connected is changed based on a procedure such as inter-PLMN handover, the MME may perform disaster roaming evaluation again. 
     9A) The MME in the first PLMN may transmit the result of the disaster roaming evaluation performed in 8A to the terminal as a NAS message. Here, the NAS message may be a detach message or a NAS message indicating a disaster roaming evaluation result. The terminal may perform a subsequent operation, such as changing the operation mode from the disaster roaming mode to the normal mode or maintaining the disaster roaming mode, based on the received NAS message. 
     Case B: When the MME does not allow disaster roaming of the terminal (when the access request of the terminal is rejected) 
     4B) The MME in the first PLMN may transmit an access rejection message to the terminal. The connection rejection message may be an attach rejection message. The access rejection message may directly or implicitly include information on disaster roaming. 
     5B) After receiving the access rejection message, the terminal evaluates the reason for rejection of the access rejection message, and then may perform PLMN re-selection. The UE may manage the priority of the PLMN based on the information on disaster roaming For example, the terminal may perform a control operation such as temporarily lowering the priority of the second PLMN in which disaster roaming has occurred or for a specific time. 
       FIGS. 20A and 20B  show an embodiment in which a second example of the disclosure of the present specification is applied to 5GS. 
     0) The terminal may configure the disaster roaming mode by user interaction or operator configuration. Specifically, when the terminal receives disaster roaming information from the network later, the terminal can be configured whether to operate in the disaster roaming mode or not by user interaction or operator configuration. For example, the disaster roaming mode setting of step 0) is a setting for whether to operate in the disaster roaming mode when a disaster roaming message is received from the network later, and is independent of whether the terminal supports the disaster roaming function, that is, it means that even a terminal supporting a roaming function may perform a different operation (eg, not operating in a disaster roaming mode) according to the settings of the user or operator. 
     1) The base station in the first PLMN may broadcast the information of the second PLMN by temporarily including the information of the second PLMN in the SIB message based on at least one of a preset policy or an operator command (OAM command) Upon receiving the SIB message including the information of the second PLMN, the terminal may recognize the base station in the first PLMN as the base station of the second PLMN and perform an operation of attempting to access the second PLMN. The SIB message may additionally include, directly or indirectly, information indicating a disaster roaming (network failure) situation. Here, the base station in the first PLMN may transmit the information of the second PLMN or information indicating the disaster roaming situation in the form of an NAS message, that is, included in the SIB message. 
     2) The terminal may transmit an access request message to attempt access to the second PLMN. Here, the access request message may be an registration request message. The access request message transmitted by the terminal is physically transmitted to the AMF in the first PLMN through the base station in the first PLMN. 
     3) The AMF in the first PLMN may determine whether to allow disaster roaming The AMF may perform an interaction with the UDM in the second PLMN to check subscriber information of the terminal that has transmitted the access request message. The AMF may check a set operator policy or a preset operator policy and preset roaming policy. If necessary, the AMF may perform interconnection with other network nodes, such as PCF, to check the operator policy. 
     Through this process, the AMF may determine whether or not to allow disaster roaming of the terminal that has transmitted the access request message (eg, whether to accept access to provide disaster roaming service to the terminal) and may determine the scope of the disaster roaming service if disaster roaming is allowed. Here, the scope of the disaster roaming service may be, for example, a basic voice call and a specific service. 
     According to the determination result of the AMF in the first PLMN, the case A operation or the case B operation may be performed. 
     Case A: When the AMF allows disaster roaming of the terminal (when the access request of the terminal is accepted) 
     4A) The AMF in the first PLMN may transmit an access acceptance message to the terminal. The connection accept message may be a registration accept message. The access acceptance message may include information on disaster roaming directly or implicitly. Here, information on disaster roaming may be included in the access acceptance message in the form of a NAS message. 
     Upon receiving the access acceptance message, the terminal may display information on disaster roaming to the user. For example, the terminal may display information on disaster roaming on the display unit of the terminal in a form or method recognizable by the user. Alternatively, the terminal may inform the user of information on disaster roaming using vibration or sound. 
     5A) The terminal may switch the operation mode to the disaster roaming mode based on information on disaster roaming included in the access acceptance message. The terminal may start applying a preset disaster roaming policy based on information on disaster roaming. 
     6A) The terminal may transmit the PDU session establishment request message to the SMF in the second PLMN via the base station and the AMF in the first PLMN. 
     The difference from the embodiment applied to the EPS described in  FIGS. 19A and 19B  is that in the embodiment applied to the 5GS, the SMF in the second PLMN may perform additional disaster roaming evaluation. For example, the SMF in the second PLMN may allow the disaster roaming service only for a specific PDU session among PDU sessions. In other words, the SMF in the second PLMN may determine the range of the emergency roaming service of the terminal. 
     The AMF in the first PLMN may communicate with the SMF (intermediate SMF (I-SMF) in  FIGS. 20A and 20B ) in the first PLMN, and the SMF in the first PLMN may communicate with the SMF in the second PLMN. That is, the SMF in the first PLMN may transmit and receive messages for communicating with the SMF in the second PLMN. The SMF in the first PLMN may perform the role of the I-SMF. 
     Alternatively, unlike shown, according to the disaster roaming deployment option, the AMF in the first PLMN may perform direct communication with the SMF in the second PLMN, which is the home PLMN of the terminal, and may transmit and receive messages with the SMF in the second PLMN. 
     Upon receiving the PDU session establishment request message, the SMF in the second PLMN may transmit the PDU session establishment response message to the terminal through the AMF of the first PLMN and the base station in the first PLMN. 
     7A) The UE may transmit IMS signaling to the IMS network (eg, PCF) in the second PLMN through the PDU session configured (established) in step 6A). Then, the terminal may be provided with an IMS-related service such as a voice service through IMS signaling. Specifically, the IMS signaling of the terminal may be transmitted to the IMS network in the second PLMN through the base station in the first PLMN, the UPF in the first PLMN (not shown in  FIGS. 20A and 20B ), and the UPF in the second PLMN. In other words, the UE may perform IMS signaling with the IMS network in the second PLMN. 
     8A) If the network node (eg, AMF) detects that the base station to which the terminal is connected is changed while the terminal is receiving a service based on disaster roaming, the AMF may perform disaster roaming evaluation again. For example, if the base station to which the terminal is connected is changed based on a procedure such as inter-PLMN handover, the AMF may perform disaster roaming evaluation again. 
     The difference from the embodiment applied to the EPS described in  FIGS. 19A and 19B  is that in the embodiment applied to the 5GS, the SMF in the second PLMN may also perform additional disaster roaming evaluation. When the SMF in the second PLMN performs additional disaster roaming evaluation, an interaction may occur between the AMF in the first PLMN, the I-SMF in the first PLMN, and the SMF in the second PLMN as needed. 
     9A) The AMF in the first PLMN may transmit the result of the disaster roaming evaluation performed in 8A to the terminal as a NAS message. Here, the NAS message may be a detach message or a NAS message indicating a disaster roaming evaluation result. The terminal may perform a subsequent operation, such as switching the operation mode from the disaster roaming mode to the normal mode or maintaining the disaster roaming mode, based on the received NAS message. 
     Case B: When the AMF does not allow disaster roaming of the terminal (when the access request of the terminal is rejected) 
     4B) The AMF in the first PLMN may transmit an access rejection message to the terminal. The connection rejection message may be an attach rejection message. The access rejection message may directly or implicitly include information on disaster roaming 
     5B) After receiving the access rejection message, the terminal evaluates the reason for rejection of the access rejection message, and then may perform PLMN re-selection. The UE may manage the priority of the PLMN based on the information on disaster roaming For example, the terminal may perform a control operation such as temporarily lowering the priority of the second PLMN in which disaster roaming has occurred or for a specific time. 
     I-3. Examples Based on SMS (Short Message Service) or MMS (Multimedia Messaging Service), etc. (3rd Example) 
     When a failure occurs in the second PLMN by the second operator, the base station in the first PLMN may broadcast an SIB message by including PLMN information of a third party (other company) (second PLMN information) in order to provide a service to a terminal (hereinafter also referred to as a second PLMN terminal) subscribed to the second PLMN in the disabled area. 
     When the terminal transmits an access request message to the network, the terminal does not recognize that a disaster roaming situation will proceed. The terminal transmits a general access request message to the base station in the first PLMN. That is, the terminal transmits the access request message to the base station in the first PLMN in the same manner as the method of transmitting the access request message to the second PLMN to which it is subscribed. 
     After the terminal normally accesses to the network through the base station in the first PLMN in a state where the terminal is not aware of the disaster roaming situation, the operator may transmit information related to S-roaming situation through at least one of SMS, MMS, and PDN connection (or PDU session) for a specific service information. 
     Upon receiving the information on the S-roaming situation, the terminal may switch the operation mode to the S-roaming mode. That is, the terminal may identify information about the S-roaming situation received through SMS, MMS, and a PDN connection (or PDU session) for a specific service, and operate in the S-roaming mode. 
     The S-roaming mode may be implemented without operating in a standardized mode for the terminal. Therefore, the terminal may not explicitly switch the operation mode to the S-roaming mode. Even if the terminal does not explicitly operate in the S-roaming mode, when the terminal performs a decision to request a service/call or performs a request operation for a network, the operator policy for a disaster situation may be reflected. 
     The third example may be performed in various communication systems. For example, the third example may be performed in EPC or 5GS. In addition, the third example may be performed between the EPC of the first operator and the 5GS of the second operator, or may be performed between the 5GS of the first operator and the EPC of the second operator. The description of  FIGS. 21A and 21B  and the description of  FIGS. 22A and 22B  to be described later are only examples, and the scope of the present specification is not limited to the description of  FIGS. 21A and 21B  and the description of  FIGS. 22A and 22B . 
       FIGS. 21A and 21B  show an embodiment in which a third example of the disclosure of the present specification is applied to EPS. 
     0) The terminal may configure the disaster roaming mode by user interaction or operator configuration. Specifically, when the terminal receives disaster roaming information from the network later, the terminal can be configured whether to operate in the disaster roaming mode or not by user interaction or operator configuration. For example, the disaster roaming mode setting of step 0) is a setting for whether to operate in the disaster roaming mode when a disaster roaming message is received from the network later, and is independent of whether the terminal supports the disaster roaming function, that is, it means that even a terminal supporting a roaming function may perform a different operation (eg, not operating in a disaster roaming mode) according to the settings of the user or operator. 
     1) The base station in the first PLMN may broadcast the information of the second PLMN by temporarily including the information of the second PLMN in the SIB message based on at least one of a preset policy or an operator command (OAM command) Upon receiving the SIB message including the information of the second PLMN, the terminal may recognize the base station in the first PLMN as the base station of the second PLMN and perform an operation of attempting to access the second PLMN. The SIB message may additionally include, directly or indirectly, information indicating a disaster roaming (network failure) situation. 
     2) The terminal may transmit an access request message to attempt access to the second PLMN. Here, the access request message may be an attach request message. The access request message transmitted by the terminal is physically transmitted to the MME in the first PLMN through the base station in the first PLMN. 
     3) The MME in the first PLMN may determine whether to allow disaster roaming The MME may perform an interaction with the HSS in the second PLMN to check subscriber information of the terminal that has transmitted the access request message. The MME may check a set operator policy or a preset operator policy and preset roaming policy. If necessary, the MME may perform interconnection with other network nodes, such as PCRF, to check the operator policy. 
     Through this process, the MME may determine whether or not to allow disaster roaming of the terminal that has transmitted the access request message (eg, whether to accept access to provide disaster roaming service to the terminal) and may determine the scope of the disaster roaming service if disaster roaming is allowed. Here, the scope of the disaster roaming service may be, for example, a basic voice call and a specific service. 
     According to the determination result of the MME in the first PLMN, the case A operation or the case B operation may be performed. 
     Case A: When the MME allows disaster roaming of the terminal (when the access request of the terminal is accepted) 
     4A) The MME in the first PLMN may process the access request of the terminal and perform a procedure for configuring (establishing) a PDN connection for service provision. The MME in the first PLMN may exchange create session request/response messages with the P-GW in the second PLMN via the S-GW in the first PLMN. 
     5A) After the MME in the first PLMN successfully configures (establishes) the PDN connection, it may transmit an access acceptance message to the terminal. The connection accept message may be an attach accept message. The access acceptance message may include information on disaster roaming directly or implicitly. 
     Upon receiving the access acceptance message, the terminal may display information on disaster roaming to the user. For example, the terminal may display information on disaster roaming on the display unit of the terminal in a form or method recognizable by the user. Alternatively, the terminal may inform the user of information on disaster roaming using vibration or sound. 
     6A) The terminal may receive an SMS or MMS message including information on disaster roaming Here, the SMS or MMS message may be transmitted from the MME. 
     The terminal may initiate a procedure for configuring (establishing) an additional PDN connection without user interaction based on previously set information on disaster roaming Here, the additional PDN connection may be used for the terminal to be connected to a specific server in case of a disaster to receive disaster-related guidance information from the specific server. Alternatively, the terminal may initiate a procedure for configuring (establishing) an additional PDN connection by user interaction. Here, the additional PDN connection may be established to connect to a server used only in case of a disaster, rather than an internet PDN used by the terminal for general communication purposes. 
     7A) The terminal may switch the operation mode to the disaster roaming mode based on information on disaster roaming included in SMS or MMS. The terminal may start applying a preset disaster roaming policy based on information on disaster roaming 
     8A) If the SMS or MMS includes information on a server that induces access in case of a disaster, the terminal may perform a procedure for configuring (establishing) a PDN connection. 
     The terminal may transmit the PDN connection request message to the P-GW in the second PLMN through the MME in the first PLMN. In addition, the P-GW in the second PLMN may transmit a response message (PDN connection accept (or reject) message) to the PDN connection request message through the MME in the first PLMN. 
     9A) The terminal may transmit IMS signaling to the IMS network (eg, P-CSCF) in the second PLMN through the PDN connection configured (established) in step 8A). Then, the terminal may be provided with an IMS-related service such as a voice service through IMS signaling. Specifically, the IMS signaling of the UE may be transmitted to the IMS network in the second PLMN via the S-GW in the first PLMN and the P-GW in the second PLMN. In other words, the UE may perform IMS signaling with the IMS network in the second PLMN. 
     10A) After receiving the response message to the PDN connection request message, the UE may change the operation mode to the disaster roaming mode and apply the disaster roaming policy. The terminal may start applying a preset disaster roaming policy based on information on disaster roaming. For reference, the disaster roaming mode conversion and application of the disaster roaming policy may be performed in step 7A), or may be performed in step 10A). 
     Case B: When the MME does not allow disaster roaming of the terminal (when the access request of the terminal is rejected) 
     If the MME does not allow disaster roaming of the terminal, even if the MME sends an SMS or MMS to the terminal, the SMS or MMS can only perform a role of an information guide message, thus description of the operation in this case is omitted. 
       FIGS. 22A and 22B  show an embodiment in which a third example of the disclosure of the present specification is applied to 5GS. 
     0) The terminal may configure the disaster roaming mode by user interaction or operator configuration. Specifically, when the terminal receives disaster roaming information from the network later, the terminal can be configured whether to operate in the disaster roaming mode or not by user interaction or operator configuration. For example, the disaster roaming mode setting of step 0) is a setting for whether to operate in the disaster roaming mode when a disaster roaming message is received from the network later, and is independent of whether the terminal supports the disaster roaming function, that is, it means that even a terminal supporting a roaming function may perform a different operation (eg, not operating in a disaster roaming mode) according to the settings of the user or operator. 
     1) The base station in the first PLMN may broadcast the information of the second PLMN by temporarily including the information of the second PLMN in the SIB message based on at least one of a preset policy or an operator command (OAM command) Upon receiving the SIB message including the information of the second PLMN, the terminal may recognize the base station in the first PLMN as the base station of the second PLMN and perform an operation of attempting to access the second PLMN. The SIB message may additionally include, directly or indirectly, information indicating a disaster roaming (network failure) situation. 
     2) The terminal may transmit an access request message to attempt access to the second PLMN. Here, the access request message may be an registration request message. The access request message transmitted by the terminal is physically transmitted to the AMF in the first PLMN through the base station in the first PLMN. 
     3) The AMF in the first PLMN may determine whether to allow disaster roaming The AMF may perform an interaction with the UDM in the second PLMN to check subscriber information of the terminal that has transmitted the access request message. The AMF may check a set operator policy or a preset operator policy and preset roaming policy. If necessary, the AMF may perform interconnection with other network nodes, such as PCF, to check the operator policy. 
     Through this process, the AMF may determine whether or not to allow disaster roaming of the terminal that has transmitted the access request message (eg, whether to accept access to provide disaster roaming service to the terminal) and may determine the scope of the disaster roaming service if disaster roaming is allowed. Here, the scope of the disaster roaming service may be, for example, a basic voice call and a specific service. 
     According to the determination result of the AMF in the first PLMN, the case A operation or the case B operation may be performed. 
     Case A: When the AMF allows disaster roaming of the terminal (when the access request of the terminal is accepted) 
     4A) The AMF in the first PLMN may transmit an access acceptance message to the terminal. The connection accept message may be a registration accept message. The access acceptance message may include information on disaster roaming directly or implicitly. Here, information on disaster roaming may be included in the access acceptance message in the form of a NAS message. 
     Upon receiving the access acceptance message, the terminal may display information on disaster roaming to the user. For example, the terminal may display information on disaster roaming on the display unit of the terminal in a form or method recognizable by the user. Alternatively, the terminal may inform the user of information on disaster roaming using vibration or sound. 
     5A) The terminal may receive an SMS or MMS message including information on disaster roaming Here, the SMS or MMS message may be transmitted from the AMF. 
     The terminal may initiate a procedure for configuring (establishing) an additional PDN connection without user interaction based on previously set information on disaster roaming Here, the additional PDN connection may be used for the terminal to be connected to a specific server in case of a disaster to receive disaster-related guidance information from the specific server. Alternatively, the terminal may initiate a procedure for configuring (establishing) an additional PDN connection by user interaction. Here, the additional PDN connection may be established to connect to a server used only in case of a disaster, rather than an internet PDN used by the terminal for general communication purposes. 
     6A) The terminal may switch the operation mode to the disaster roaming mode based on information on disaster roaming included in SMS or MMS. The terminal may start applying a preset disaster roaming policy based on information on disaster roaming 
     7A) If the SMS or MMS includes information on a server inducing access in case of a disaster, the terminal may perform a procedure for configuring (establishing) a PDU session. 
     The AMF in the first PLMN may communicate with the SMF (intermediate SMF (I-SMF) in  FIGS. 22A and 22B ) in the first PLMN, and the SMF in the first PLMN may communicate with the SMF in the second PLMN. That is, the SMF in the first PLMN may transmit and receive messages for communicating with the SMF in the second PLMN. The SMF in the first PLMN may perform the role of the I-SMF. 
     Alternatively, unlike shown, according to the disaster roaming deployment option, the AMF in the first PLMN may perform direct communication with the SMF in the second PLMN, which is the home PLMN of the terminal, and may transmit and receive messages with the SMF in the second PLMN. 
     Upon receiving the PDU session establishment request message, the SMF in the second PLMN may transmit the PDU session establishment response message to the terminal through the AMF of the first PLMN and the base station in the first PLMN. 
     8A) The UE may transmit IMS signaling to the IMS network (eg, PCF) in the second PLMN through the PDU session configured (established) in step 7A). Then, the terminal may be provided with an IMS-related service such as a voice service through IMS signaling. Specifically, the IMS signaling of the terminal may be transmitted to the IMS network in the second PLMN through the base station in the first PLMN, the UPF in the first PLMN (not shown in  FIGS. 22A and 22B ), and the UPF in the second PLMN. In other words, the UE may perform IMS signaling with the IMS network in the second PLMN. 
     9A) After receiving the response message to the PDU session request message, the UE may switch the operation mode to the disaster roaming mode and apply the disaster roaming policy. The terminal may start applying a preset disaster roaming policy based on information on disaster roaming For reference, the disaster roaming mode switching and application of the disaster roaming policy may be performed in step 6A) or step 9A). 
     Case B: When the AMF does not allow the terminal&#39;s disaster roaming (when the terminal&#39;s access request is rejected) 
     If the AMF does not allow disaster roaming of the terminal, even if the AMF sends an SMS or MMS to the terminal, the SMS or MMS can only perform a role of an information guide message, thus in the embodiment of  FIGS. 21A and 21B , a description of the operation in the case of failure is omitted. 
     The contents described so far may be implemented in hardware. For example, the contents described so far may be applied to the hardware to be described with reference to  FIGS. 13 to 25 . 
     I-4. Example of Operation of the Terminal 
     The contents of the disclosure of the present specification described above with reference to  FIGS. 15 to 22B  (the first example, the second example, the third example, etc.) may be applied to the operation of the terminal. The terminal may operate according to any one of the examples of the disclosure of the present specification described above, or may operate according to a combination of at least one of the examples of the disclosure of the present specification. Hereinafter, an example of the operation of the terminal will be described in detail. The operation of the terminal already described in the contents of the disclosure of the present specification (the first example, the second example, the third example, etc.) 3, etc.) is omitted, and an example of the operation of the terminal will be described with a focus on contents not described in the above. 
     The terminal may recognize the S-roaming situation based on information received from the network node (eg, disaster roaming information received through at least one of AS signaling, NAS signaling, or SMS/MMS signaling). The UE (if necessary) performs PLMN selection again. In managing the priority of the roaming PLMN selection, the UE may manage the rejection by the PLMN and the network node regarding S-roaming received from the network node in addition to general priority management. 
     The terminal may perform an operation of switching to the S-roaming mode or applying the policy of the S-roaming mode according to a preset(pre-configured) operator policy. The terminal may receive information on roaming settings related to the S-roaming mode from the user. 
       FIG. 23  is a flowchart illustrating an example of an operation of a terminal. 
       FIG. 23  is only a flowchart showing an example of the operation of the terminal, and the range of the operation of the terminal is not limited to the contents shown in  FIG. 23 . The terminal may also perform the operation related to the terminal described above and the operation related to the terminal to be described later in  FIG. 23 . 
     In step S 2301 , the terminal may receive information about the second PLMN to which the terminal is subscribed from the base station in the first PLMN. Here, the information on the second PLMN may be transmitted by the base station in the first PLMN based on the occurrence of a failure in the second PLMN. 
     In step S 2302 , the terminal may access the first PLMN through the base station in the first PLMN based on the information on the second PLMN. For example, the terminal may be connected to at least one network node in the first PLMN and at least one network node in the second PLMN through a base station in the first PLMN. 
     In step S 2303 , the terminal may display information informing of a failure occurring in the second PLMN on the display of the terminal. The information indicating the failure may be information indicating that the second PLMN has failed and accessed the first PLMN through the base station in the first PLMN. The information indicating the failure may include a list of limited services provided by the first PLMN. Here, the list of limited services may be received through the base station of the first PLMN after the terminal roams to the first PLMN, or may be received through the base station of the second PLMN before the terminal roams to the first PLMN. 
     The terminal may change the operation mode of the terminal to the disaster roaming mode based on the roaming policy related to the failure occurring in the second PLMN. The roaming policy related to the failure occurring in the second PLMN may be a disaster roaming policy preset(preconfigured) by the second operator of the second PLMN. Here, the disaster roaming mode may be an operation mode that operates based on a roaming setting related to a failure of the second PLMN. Here, the roaming setting may include at least one of the aforementioned disaster roaming policy or a roaming setting set by a user. For reference, an example of setting roaming settings by a user will be described with reference to  FIG. 32 . 
     As in the example of  FIG. 32 , when the terminal displays the emergency roaming setting, the terminal may receive information on the roaming setting(ie, the emergency roaming setting of  FIG. 32 ) related to the failure from the user. For reference, emergency roaming is the same as disaster roaming, S-roaming, or E-roaming in the disclosure of this specification. 
     The terminal may display information informing of a failure on the display of the terminal in various ways as illustrated in  FIGS. 24 to 32  to be described later. 
       FIG. 24  is a first exemplary diagram illustrating a screen of a terminal according to an embodiment. 
     Hereinafter, “screen” is used in the same sense as display. 
     Referring to  FIG. 24 , referring to  FIG. 15 , when the processor of the terminal roams to cope with the failure situation as described above, unlike an roaming icon generally displayed, an icon  1041 - 12  for indicating a corresponding situation (ie, a situation in which S-roaming or E-roaming is performed to cope with a failure situation) may be displayed on the status bar displayed on the display  1041 . The icon  1041 - 12  may indicate that the roaming mode has been switched to cope with the failure situation or may mean that a specific roaming policy is applied. The icon  1041 - 12  may be an ER indicating emergency roaming or an SR indicating special roaming 
     The icon  1041 - 12  may have a different shape from a general icon (ie, an icon indicating a state of simply receiving information or recognizing such a state). Alternatively, although the shape is the same, the displayed form may be different. For example, the icon  1041 - 12  is displayed while blinking, but a general icon may be displayed without blinking. 
     Meanwhile, various icons representing different information may be displayed on the display  1041 . Also, as described above, the shape, shape (eg, blinking), and color of the display (eg, icon, notification window, etc.) of these various icons may be changed according to the level of recognition of the terminal and the application level of the roaming mode. 
     In addition, information  1041 - 13  indicating the signal strength from the base station of the first PLMN may be displayed on the status bar displayed on the display  1041  according to roaming to cope with a failure situation. 
     Also, information indicating that the service of the second PLMN is impossible (eg, No Service)  1041 - 11  may be displayed on a status bar displayed on the display  1041 . 
     For reference, although an example in which information  1041 - 13  and  1041 - 11  and an icon  1041 - 12  that can be visually confirmed by a user are displayed is shown in  FIG. 24 , this is only an example. In addition to the visual method, the terminal may transmit information about the failure situation to the user together or independently by using a method such as vibration or sound, etc. 
     The description of the information  1041 - 13  and  1041 - 11  and the icon  1041 - 12  displayed on the display  1041  in  FIG. 24  is applied equally to the information  1041 - 13  and  1041 - 11  displayed on the display in  FIGS. 25 to 33 . A description of the information  1041 - 13  and  1041 - 11  and the icon  1041 - 12  displayed on the display in  FIGS. 25 to 33  will be omitted. 
       FIG. 25  is a second exemplary diagram illustrating a screen of a terminal according to an embodiment. 
     When the terminal is successfully connected to the network, the terminal may display a message  1041 - 14  on the display  1041  indicating that it has roamed to cope with a failure situation. That is, the terminal may display the message  1041 - 14  received from the server on the display  1041 . In this case, information on available services (eg, a list of voice calls, text services, and limited data services, etc.) may be displayed in the message  1041 - 14  along with a description of the corresponding roaming mode situation. Here, in the message  1041 - 14 , a hyperlink  1041 - 15  for notifying detailed information, such as the content of each service, may be displayed. When the hyperlink  1041 - 15  is selected (eg, when the hyperlink  1041 - 15  is touched by the user), a connection to a server capable of providing the corresponding content is performed. That is, the terminal may perform a PDN connection request or a PDU session connection request to the corresponding server. 
       FIG. 26  is a third exemplary diagram illustrating a screen of a terminal according to an embodiment. 
     Referring to  FIG. 26 , the terminal may display a message  1041 - 16  indicating that it has roamed to cope with a failure situation on the display  1041 . 
     Meanwhile, in the message  1041 - 16 , information on available services may be displayed along with a description of the corresponding roaming Specifically, the message may indicate that only voice calls, text services, and limited data services are available, and other services are unavailable. 
       FIG. 27  is a fourth exemplary diagram illustrating a screen of a terminal according to an embodiment. 
     As can be seen with reference to  FIG. 27 , when S-roaming or E-roaming is performed to cope with a failure situation, the terminal may operates in a predetermined mode for E-Roaming or S-roaming, for example, as in the safe mode provided by Microsoft&#39;s Windows. The screen according to the predetermined operation mode may have different resolution, color, and font like the safe mode screen of a Windows PC. 
     Specifically, when S-roaming or E-roaming is performed to cope with a failure situation, the terminal does not display icons of all installed applications, and only displays icons of executable applications (eg, a phone application and a text message application). That is, icons of non-executable applications may not be displayed at all. Alternatively, icons of non-executable applications may be displayed in shades or black and white or transparent, while icons of executable applications may be displayed in color. 
     In addition, the terminal may display a preset background screen image instead of a background screen image designated by the user. Alternatively, as shown, the terminal may display information indicating that only a limited service is available in the background screen image. 
     If the user executes the phone application, the terminal may display a screen as shown in  FIG. 27 . 
       FIG. 28  is a fifth exemplary diagram illustrating a screen of a terminal according to an embodiment. 
     A fifth exemplary view is an exemplary view showing a screen displayed by a phone application executed in a terminal. Referring to  FIG. 28 , information  1041 - 16  for indicating that roaming has been performed in order to cope with a failure situation may be displayed on a screen displayed by a phone application executed in the terminal. 
     That is, on the screen displayed by the phone application running on the terminal, a guide message indicating that the user has emergency roamed to a third party (other company) due to a failure situation may be displayed. 
     Also, an icon  1041 - 12  indicating that roaming has been performed to cope with a failure situation may be displayed on a status bar displayed on the display  1041 . 
     If an application other than the phone call and message is executed by the user, the screen of the corresponding application may display a notification message, a pop-up message, or a guide message informing that the application is unavailable. 
     Meanwhile, as described above, a predetermined mode for S-roaming or E-roaming may be applied when set by a user as described below. 
       FIG. 29  is a sixth exemplary diagram illustrating a screen of a terminal according to an embodiment. 
     A sixth exemplary diagram is an exemplary diagram illustrating a setting screen of a terminal. As shown in  FIG. 29 , when the service is unavailable due to a failure of the second PLMN, the terminal performs roaming to the first PLMN and may display a screen for receiving a user&#39;s setting as to whether to use even a limited service. When the user inputs allow, and when the first PLMN becomes unavailable due to a failure, a screen may be displayed as shown in  FIGS. 24 to 28 . 
       FIG. 30  is a seventh exemplary diagram illustrating a screen of a terminal according to an embodiment. 
     A seventh exemplary diagram is a first example illustrating a screen when roaming to the first PLMN is attempted but roaming fails when the service is unavailable due to a failure of the second PLMN. 
     Referring to  FIG. 30 , information  1041 - 18  informing that the terminal attempted to roam to the first PLMN to cope with a failure situation but the roaming was failed may be displayed on the display  1041  of the terminal. In addition, the information  1041 - 18  may include content notifying that a communication service is not available. 
     The information  1041 - 18  may be displayed on the display  1041  for a certain period of time (eg, 5 seconds or 10 seconds, etc.) and disappear. Alternatively, the information  1041 - 18  may continue to be displayed until the failure occurring in the second PLMN is resolved. 
       FIG. 30  and  FIGS. 31A and 31B , which will be described later, show examples in which information ( 1041 - 18 ,  1041 - 19  of  FIG. 31A, 1041-20  of  FIG. 32B ) that can be visually confirmed by a user is displayed, but this is only an example. In addition to the visual method, the terminal may transmit information notifying the user that the roaming attempt has failed together or independently by using a method such as vibration or sound, etc. 
       FIG. 31A  is an eighth exemplary view illustrating a screen of a terminal according to an embodiment. 
     The eighth exemplary view is a second example illustrating a screen when roaming to the first PLMN is attempted but roaming fails when the service is unavailable due to a failure of the second PLMN. 
     Referring to  FIG. 31A , the information  1041 - 19  displayed on the display  1041  of the terminal may includes contents indicating that the terminal attempted to roam to the first PLMN in order to cope with a failure situation, but failed, and asking whether to attempt roaming to other PLMNs (e.g. the third PLMN of operator  3 ) other than the first PLMN. 
     If the user selects ‘Yes’, the terminal may attempt disaster roaming to the third PLMN. If the user selects ‘No’, the terminal may not attempt disaster roaming to the third PLMN. When the user selects ‘No’, the terminal may display the information  1041 - 18  of  FIG. 30  on the display  1041  to inform the user that the service is unavailable. 
     For reference, the user&#39;s selection of ‘yes’ or ‘no’ may be input to the terminal in various ways, such as the user&#39;s touch on the display, voice recognition, or movement of the terminal by the user. 
     If the user does not select both ‘yes’ and ‘no’ for a preset period of time (eg, 10 seconds or 1 minute), the terminal may attempt disaster roaming to the third PLMN. Alternatively, if the user does not select both ‘yes’ and ‘no’ for a preset period of time (eg, 10 seconds or 1 minute), the terminal may not attempt disaster roaming to the third PLMN. 
       FIG. 31B  is a ninth exemplary diagram illustrating a screen of a terminal according to an embodiment. 
     The ninth exemplary diagram is a third example illustrating a screen when roaming to the first PLMN is attempted but roaming fails when the service is unavailable due to a failure of the second PLMN. 
     Referring to  FIG. 31   b,  the information  1041 - 19  displayed on the display  1041  of the terminal may includes contents indicating that the terminal attempted to roam to the first PLMN in order to cope with a failure situation, but failed, and asking whether to attempt roaming to other PLMNs (e.g. the third PLMN of operator  3 ) other than the first PLMN. 
     When the service is unavailable due to a failure of the second PLMN, the UE attempts to roam to the first PLMN, but when roaming fails, it may attempt to roam to the third PLMN of a third operator. 
     The information  1041 - 20  may be displayed on the display  1041  for a certain period of time (eg, 5 seconds or 10 seconds, etc.) and disappear. Alternatively, the information  1041 - 20  may be continuously displayed until the terminal succeeds or fails roaming to the third PLMN. 
       FIG. 32  is a tenth exemplary diagram illustrating a screen of a terminal according to an embodiment. 
     A tenth exemplary diagram is an exemplary diagram illustrating an emergency roaming setting screen of a terminal. 
     As shown in  FIG. 32 , the terminal may display an emergency roaming setting screen  1041 - 21  on the display  1041 . The emergency roaming setting screen  1041 - 21  is a screen for indicating various settings related to emergency roaming and receiving an input of settings for emergency roaming from a user. 
     The terminal may display various settings on the emergency roaming setting screen  1041 - 21 , such as notification settings, settings for services limited during emergency roaming, and whether to attempt roaming to another PLMN when emergency roaming fails, etc. 
     For example, on the emergency roaming setting screen  1041 - 21 , a setting screen  1041 - 22  related to a notification when the terminal roams to another PLMN due to a failure in the subscribed second PLMN may be displayed. The setting screen  1041 - 22  may display setting information for notifications, such as screen display, vibration, and sound, together or independently. The user may input a notification setting for emergency roaming by selecting at least one of screen display, vibration, or sound. 
     In addition, the user may input detailed settings for each notification method, such as screen display, vibration, and sound, together or independently. For example, when the user selects ‘display screen’, the user may set a notification for emergency roaming is displayed on the display  1041  in which form, method, and the like. If the user selects ‘Vibration’, the user can set the number of vibrations, vibration intensity, duration of vibration, etc. of the notification during emergency roaming If the user selects ‘Sound’, the user can set the sound type, volume, sound duration, etc. of the notification during emergency roaming 
     For reference, the emergency roaming setting screen  1041 - 21  may be displayed before emergency roaming, when emergency roaming is attempted, or after emergency roaming When the emergency roaming setting screen  1041 - 21  is displayed before emergency roaming, the information  1041 - 11  and  1041 - 13  and the icon  1041 - 12  may not be displayed on the display  1041 . 
     During emergency roaming, the terminal may operate in the emergency roaming mode based on the emergency roaming setting input by the user through the emergency roaming setting screen  1041 - 21 . 
       FIG. 33  illustrates a wireless communication system according to an embodiment. 
     Referring to  FIG. 33 , the wireless communication system may include a first device  100   a  and a second device  100   b.    
     The first device  100   a  may be a device related to a base station, a network node, a transmission terminal, a reception terminal, a wireless device, a wireless communication device, a vehicle, a vehicle on which a self-driving function is mounted, a connected car, a drone (unmanned aerial vehicle (UAV)), an artificial intelligence (AI) module, a robot, an augmented reality (AR) device, a virtual reality (VR) device, a mixed reality (MR) device, a hologram device, a public safety device, an MTC device, an IoT device, a medical device, a FinTech device (or financial device), a security device, a climate/environment device, a device related to 5G service or a device related to the fourth industrial revolution field. 
     The second device  100   b  may be a device related to a base station, a network node, a transmission terminal, a reception terminal, a radio device, a wireless communication device, a vehicle, a vehicle on which a self-driving function is mounted, a connected car, a drone (unmanned aerial vehicle (UAV)), an artificial intelligence (AI) module, a robot, an augmented reality (AR) device, a virtual reality (VR) device, a mixed reality (MR) device, a hologram device, a public safety device, an MTC device, an IoT device, a medical device, a FinTech device (or financial device), a security device, a climate/environment device, a device related to 5G service or a device related to the fourth industrial revolution field. 
     For example, the UE may include a cellular phone, a smart phone, a laptop computer, a terminal for digital broadcasting, a personal digital assistants (PDA), a portable multimedia player (PMP), a navigation, a slate PC, a tablet PC, an ultrabook, a wearable device (e.g., a watch type terminal (smartwatch), a glass type terminal (smart glass), a head mounted display (HMD)), and so on. For example, the HMD may be a display device of a form, which is worn on the head. For example, the HMD may be used to implement VR, AR or MR. 
     For example, the drone may be a flight vehicle that flies by a wireless control signal without a person being on the flight vehicle. For example, the VR device may include a device implementing the object or background of a virtual world. For example, the AR device may include a device implementing the object or background of a virtual world by connecting it to the object or background of the real world. For example, the MR device may include a device implementing the object or background of a virtual world by merging it with the object or background of the real world. For example, the hologram device may include a device implementing a 360-degree stereographic image by recording and playing back stereographic information using the interference phenomenon of a light beam generated when two lasers called holography are met. For example, the public safety device may include a video relay device or an imaging device capable of being worn on a user&#39;s body. For example, the MTC device and the IoT device may be a device that does not require a person&#39;s direct intervention or manipulation. For example, the MTC device and the IoT device may include a smart meter, a vending machine, a thermometer, a smart bulb, a door lock or a variety of sensors. For example, the medical device may be a device used for the purpose of diagnosing, treating, reducing, handling or preventing a disease. For example, the medical device may be a device used for the purpose of diagnosing, treating, reducing or correcting an injury or obstacle. For example, the medical device may be a device used for the purpose of testing, substituting or modifying a structure or function. For example, the medical device may be a device used for the purpose of controlling pregnancy. For example, the medical device may include a device for medical treatment, a device for operation, a device for (external) diagnosis, a hearing aid or a device for a surgical procedure. For example, the security device may be a device installed to prevent a possible danger and to maintain safety. For example, the security device may be a camera, CCTV, a recorder or a blackbox. For example, the FinTech device may be a device capable of providing financial services, such as mobile payment. For example, the FinTech device may include a payment device or point of sales (POS). For example, the climate/environment device may include a device for monitoring or predicting the climate/environment. 
     The first device  100   a  may include at least one processor such as a processor  1020   a,  at least one memory such as memory  1010   a,  and at least one transceiver such as a transceiver  1031   a.  The processor  1020   a  may perform the above-described functions, procedures, and/or methods. The processor  1020   a  may perform one or more protocols. For example, the processor  1020   a  may perform one or more layers of a radio interface protocol. The memory  1010   a  is connected to the processor  1020   a,  and may store various forms of information and/or instructions. The transceiver  1031   a  is connected to the processor  1020   a,  and may be controlled to transmit and receive radio signals. 
     The second device  100   b  may include at least one processor such as a processor  1020   b,  at least one memory device such as memory  1010   b,  and at least one transceiver such as a transceiver  1031   b.  The processor  1020   b  may perform the above-described functions, procedures and/or methods. The processor  1020   b  may implement one or more protocols. For example, the processor  1020   b  may implement one or more layers of a radio interface protocol. The memory  1010   b  is connected to the processor  1020   b,  and may store various forms of information and/or instructions. The transceiver  1031   b  is connected to the processor  1020   b  and may be controlled transmit and receive radio signals. 
     The memory  1010   a  and/or the memory  1010   b  may be connected inside or outside the processor  1020   a  and/or the processor  1020   b,  respectively, and may be connected to another processor through various technologies, such as a wired or wireless connection. 
     The first device  100   a  and/or the second device  100   b  may have one or more antennas. For example, an antenna  1036   a  and/or an antenna  1036   b  may be configured to transmit and receive radio signals. 
     &lt;Scenarios to which the Disclosure of the Present Disclosure is Applicable&gt; 
     Hereinafter, scenarios to which the present disclosure is applicable are described. 
     In the present disclosure, an always-on PDU session for URLLC having a low-latency characteristic may be used for artificial intelligence, robots, autonomous driving, extended reality, and the like among the 5G scenarios below. 
       FIG. 34  illustrates an example of 5G use scenarios. 
     The 5G usage scenarios illustrated in  FIG. 34  are merely exemplary, and the technical features of the present disclosure may also be applied to other 5G usage scenarios that are not illustrated in  FIG. 34 . 
     Referring to  FIG. 34 , three major requirement areas of 5G include: (1) an enhanced mobile broadband (eMBB) area, (2) a massive machine type communication (mMTC) area, and (3) an ultra-reliable and low latency communications (URLLC) area. Some examples of usage may require multiple areas for optimization, while other examples of usage may focus only on one key performance indicator (KPI). The 5G supports these various examples of usage in a flexible and reliable way. 
     The eMBB focuses generally on improvements in data rate, latency, user density, and capacity and coverage of mobile broadband access. The eMBB aims at a throughput of about 10 Gbps. The eMBB makes it possible to far surpass basic mobile Internet access, and covers full-duplex operations, media in cloud or augmented reality, and entertainment applications. Data is one of the key drivers of 5G, and it may not be possible to see dedicated voice services for the first time in the 5G era. In 5G, voice is expected to be processed as an application program simply using data connection provided by a communication system. A main reason for an increased traffic volume is an increase in content size and an increase in the number of applications requiring high data rates. Streaming services (audio and video), interactive video and mobile Internet connections will become more prevalent as more devices are connected to the Internet. Many of these applications require always-on connectivity to push real-time information and notifications to users. Cloud storage and applications are rapidly increasing in mobile communication platforms, which may be applied to both work and entertainment. Cloud storage is a special use case that drives the growth of uplink data rates. 5G is also used for remote work in the cloud and requires much lower end-to-end latency to maintain a good user experience when tactile interfaces are used. In entertainment, for example, cloud gaming and video streaming are another key factor requiring improvement in mobile broadband capabilities. Entertainment is essential on smartphones and tablets anywhere, including in highly mobile environments such as trains, cars and airplanes. Another use case is augmented reality and information retrieval for entertainment. Here, augmented reality requires very low latency and an instantaneous data amount. 
     The mMTC, which is designed to enable communication between a large number of low-cost devices powered by batteries, is provided to support smart metering, logistics, fields, and applications such as body sensors. The mMTC aims at about 10-year batteries and/or about one million devices per km2. The mMTC enables seamless connection of embedded sensors in all fields to form a sensor network and is one of the most anticipated 5G use cases. Potentially, IoT devices are predicted to reach 20.4 billion by 2020. Smart networks utilizing industrial IoT is one of the areas where 5G plays a key role in enabling smart cities, asset tracking, smart utilities, agriculture and security infrastructure. 
     The URLLC, which enables devices and machines to communicate with high reliability, very low latency, and high availability, are ideal for vehicle communications, industrial control, factory automation, telesurgery, smart grid, and public safety applications. The URLLC aims at a delay of about 1 ms. The URLLC includes new services that will change the industry through ultra-reliable/low-latency links such as remote control of key infrastructures and autonomous vehicles. Levels of reliability and latency are essential for smart grid control, industrial automation, robotics, and drone control and adjustment. 
     Next, a plurality of usage examples included in the triangle of  FIG. 34  will be described in more detail. 
     5G, which is a means of providing streams that are rated as hundreds of megabits per second to a gigabit per second, may complement fiber-to-the-home (FTTH) and cable-based broadband (or data over cable service interface specifications (DOCSIS)). Such a high speed may be required to deliver TVs with resolution of 4K or higher (6K, 8K and higher) as well as virtual reality (VR) and augmented reality (AR). VR and AR applications involve almost immersive sports events. Specific applications may require special network configuration. For example, in the case of VR games, a game company may need to integrate a core server with an edge network server of a network operator to minimize latency. 
     Automotive is expected to be an important new driver for 5G together with many use cases for mobile communication regarding vehicles. For example, entertainment for passengers require both high capacity and high mobile broadband. The reason is because future users will continue to expect high-quality connections, regardless of their location and speed. Another use case in the automotive sector is an augmented reality dashboard. The augmented reality dashboard allows drivers to identify objects in the dark on top of what they see through a front window. The augmented reality dashboard superimposes information to be provided to the driver regarding a distance and movement of objects. In the future, wireless modules will enable communication between vehicles, exchange of information between a vehicle and a supporting infrastructure, and exchange of information between a vehicle and other connected devices (e.g., devices carried by pedestrians). A safety system may lower the risk of accidents by guiding the driver to alternative courses of action to make driving safer. A next step will be a remotely controlled vehicle or an autonomous vehicle. This requires very reliable and very fast communication between different autonomous vehicles and/or between vehicles and infrastructure. In the future, autonomous vehicles will perform all driving activities and drivers will be forced to focus only on traffic anomalies that the vehicle itself cannot identify. The technical requirements of autonomous vehicles require ultra-low latency and ultra-fast reliability to increase traffic safety to levels that cannot be achieved by humans. 
     Smart cities and smart homes referred to as smart society will be embedded with high-density wireless sensor networks as an example of smart networks. A distributed network of intelligent sensors will identify the conditions for cost and energy efficient maintenance of a city or home. A similar setup may be done for each household. Temperature sensors, window and heating controllers, burglar alarms, and home appliances are all wirelessly connected. Many of these sensors typically require low data rates, low power, and low cost. However, for example, real-time HD video may be required in certain types of devices for surveillance. 
     The consumption and distribution of energy including heat or gas is highly decentralized, requiring automated control of distributed sensor networks. A smart grid interconnects these sensors using digital information and communication technologies to collect information and act accordingly. This information may include the behavior of suppliers and consumers, so that the smart grid may improve efficiency, reliability, economical efficiency, sustainability of production, and a distribution of fuels such as electricity in an automated manner The smart grid may also be considered as another low-latency sensor network. 
     A health sector has many applications that may benefit from mobile communications. The communication system may support telemedicine providing clinical care from remote locations. This may help reduce barriers to distance and improve access to medical services that are not consistently available in remote rural areas. It is also used to save lives in critical care and emergencies. A wireless sensor network based on mobile communication may provide remote monitoring and sensors for parameters such as a heart rate and blood pressure. 
     Wireless and mobile communications are becoming increasingly important in industrial applications. Wiring is expensive to install and maintain. Thus, a possibility of replacing cables with reconfigurable wireless links is an attractive opportunity for many industries. However, achieving this requires that a wireless connection operates with a delay, reliability and capacity similar to those of a cable and requires simplified management. Low latency and very low error probability are new requirements that need to be connected to 5G. 
     Logistics and cargo tracking is an important use case for mobile communications that enables tracking of inventory and packages from anywhere using a location-based information system. Logistics and freight tracking use cases typically require low data rates but require a wide range and reliable location information. 
     &lt;Artificial Intelligence (AI)&gt; 
     Artificial intelligence refers to a field of studying artificial intelligence or a methodology for creating the same, and machine learning refers to a field of defining various problems dealing in an artificial intelligence field and studying methodologies for solving the same. The machine learning may be defined as an algorithm for improving performance with respect to a certain task through repeated experiences with respect to the task. 
     An artificial neural network (ANN) is a model used in machine learning. It can mean a whole model of problem-solving ability, consisting of artificial neurons (nodes) that form a network of synapses. An ANN can be defined by a connection pattern between neurons in different layers, a learning process for updating model parameters, and/or an activation function for generating an output value. 
     The artificial neural network may include an input layer, an output layer, and optionally one or more hidden layers. Each layer includes one or more neurons, and the artificial neural network may include neurons and synapses connecting neurons. In the artificial neural network, each neuron may output a function value of an activation function for input signals, weights, and biases input through synapses. 
     Model parameters refer to parameters determined through learning, and include the weight of synaptic connections and the bias of neurons. In addition, the hyperparameter refers to a parameter that must be set before learning in a machine learning algorithm, and includes a learning rate, the number of iterations, a mini-batch size, an initialization function, and the like. 
     The purpose of learning artificial neural networks can be seen as determining the model parameters that minimize the loss function. The loss function may be used as an index for determining optimal model parameters in the learning process of the artificial neural network. 
     Machine learning can be classified into supervised learning, unsupervised learning, and reinforcement learning according to a learning method. 
     Supervised learning refers to a method of training an artificial neural network in a state where a label for the learning data is given, and the label may mean the correct answer (or result value) that the artificial neural network must infer when the learning data is input to the artificial neural network. Unsupervised learning may refer to a method of training an artificial neural network in a state where no labels are given for training data. Reinforcement learning can refer to a learning method in which an agent defined in an environment learns to select an action or sequence of actions that maximizes the cumulative reward in each state. 
     Among artificial neural networks, machine learning implemented as a deep neural network (DNN) including a plurality of hidden layers is also called deep learning, and deep learning is a part of machine learning. Hereinafter, machine learning is used in a sense including deep learning. 
     &lt;Robot&gt; 
     A robot may refer to a machine which automatically handles a given task by its own ability, or which operates autonomously. Particularly, a robot that functions to recognize an environment and perform an operation according to its own judgment may be referred to as an intelligent robot. 
     Robots may be classified into, for example, industrial, medical, household, and military robots, according to the purpose or field of use. 
     A robot may include an actuator or a driving unit including a motor in order to perform various physical operations, such as moving joints of the robot. In addition, a movable robot may include, for example, a wheel, a brake, and a propeller in the driving unit thereof, and through the driving unit, may thus be capable of traveling on the ground or flying in the air. 
     &lt;Self-Driving or Autonomous-Driving&gt; 
     Autonomous driving refers to self-driving technology, and an autonomous vehicle refers to a vehicle that moves without any manipulation by a user or with minimum manipulation by a user. 
     For example, autonomous driving may include all of a technology for keeping a vehicle within a driving lane, a technology for automatically controlling a speed such as an adaptive cruise control, a technology for automatically driving the vehicle along a determined route, and a technology for, when a destination is set, automatically setting a route and driving the vehicle along the route. 
     A vehicle includes a vehicle having only an internal combustion engine, a hybrid vehicle having both an internal combustion engine and an electric motor, and an electric vehicle having only an electric motor, and may include not only an automobile but also a train, a motorcycle, or the like. 
     In this case, an autonomous vehicle may be considered as a robot with an autonomous driving function. 
     &lt;Extended Reality; XR&gt; 
     Extended reality collectively refers to virtual reality (VR), augmented reality (AR), and mixed reality (MR). The VR technology provides real world objects or backgrounds only in CG images, the AR technology provides virtual CG images together with real object images, and the MR technology is computer graphic technology for mixing and combining virtual objects with the real world. 
     The MR technology is similar to the AR technology in that both real and virtual objects are shown together. However, there is a difference in that a virtual object is used to complement a real object in the AR technology, whereas a virtual object and a real object are used in an equivalent nature in the MR technology. 
     The XR technology may be applied to a head-mount display (HMD), a head-up display (HUD), a mobile phone, a tablet PC, a laptop, a desktop, a TV, digital signage, etc. A device to which the XR technology is applied may be referred to as an XR device. 
       FIG. 35  shows an AI system  1  according to an embodiment. 
     Referring to  FIG. 35 , an AI system  1  is connected to at least one of an AI server  200 , a robot  100   a,  a self-driving vehicle  100   b,  an XR device  100   c,  a smartphone  100   d,  or home appliances  100   e  over a cloud network  10 . In this case, the robot  100   a,  the self-driving vehicle  100   b,  the XR device  100   c,  the smartphone  100   d  or the home appliances  100   e  to which the AI technology has been applied may be called AI devices  100   a  to  100   e.    
     The cloud network  10  may be a network that constitutes a part of a cloud computing infrastructure or a network that exists in the cloud computing infrastructure. Here, the cloud network  10  may be configured using a 3G network, a 4G or long term evolution (LTE) network, or a 5G network. 
     The devices  100   a  to  100   e  and  200  configuring the AI system  1  may be interconnected over the cloud network. Particularly, the devices  100   a  to  100   e  and  200  may communicate with each other through a base station but may directly communicate with each other without the intervention of a base station. 
     The AI server  200  may include a server that performs AI processing and a server that performs an operation on big data. 
     The AI server  200  is connected to at least one of the robot  100   a,  the self-driving vehicle  100   b,  the XR device  100   c,  the smartphone  100   d  or the home appliances  100   e,  that is, AI devices configuring the AI system, over the cloud network  10  and may help at least some of the AI processing of the connected AI devices  100   a  to  100   e.    
     In this case, the AI server  200  may train an artificial neural network based on a machine learning algorithm in place of the AI devices  100   a  to  100   e,  may directly store a learning model or may transmit the learning model to the AI devices  100   a  to  100   e.    
     In this case, the AI server  200  may receive input data from the AI devices  100   a  to  100   e,  may deduce a result value of the received input data using the learning model, may generate a response or control command based on the deduced result value, and may transmit the response or control command to the AI devices  100   a  to  100   e.    
     Alternatively, the AI devices  100   a  to  100   e  may directly deduce a result value of input data using a learning model and may generate a response or control command based on the deduced result value. 
     Hereinafter, various embodiments of the AI devices  100   a  to  100   e  to which the aforementioned technology is applied will be described. 
     &lt;AI+Robot&gt; 
     The robot  100   a,  which adopts an AI technology, may be implemented as a guide robot, a transport robot, a cleaning robot, a wearable robot, an entertainment robot, a pet robot, an unmanned flying robot, and the like. 
     The robot  100   a  may include a robot control module for controlling an operation, and the robot control module may refer to a software module or a chip implemented with hardware. 
     The robot  100   a  may acquire status information of the robot  100   a  using sensor information acquired from various types of sensors, detect (recognize) surrounding environments and objects, generate map data, determine moving routes and driving plans, determine responses to user interactions, or determine actions. 
     Here, the robot  100   a  may use sensor information obtained from at least one sensor from among lidar, radar, and camera to determine a moving route and a driving plan. 
     The robot  100   a  may perform the above operations using a learning model including at least one artificial neural network. For example, the robot  100   a  may recognize a surrounding environment and an object using a learning model and may determine an operation using the recognized surrounding environment information or object information. Here, the learning model may be directly learned by the robot  100   a  or learned by an external device such as the AI server  200 . 
     Here, the robot  100   a  may directly generate a result using a learning model and perform an operation, or transmit sensor information to an external device such as the AI server  200 , receive a result generated accordingly, and perform an operation. 
     The robot  100   a  may determine a moving path and a driving plan using at least one of map data, object information detected from sensor information, or object information acquired from an external device, and control a driving unit to drive the robot  100   a  according to the moving path and the driving plan. 
     The map data may include object identification information on various objects arranged in a space in which the robot  100   a  moves. For example, the map data may include object identification information on fixed objects such as walls and doors and movable objects such as flower pots and desks. In addition, the object identification information may include a name, a type, a distance, and a location. 
     In addition, the robot  100   a  may perform an operation or run by controlling the driving unit based on the user&#39;s control/interaction. In this case, the robot  100   a  may acquire interaction intention information according to a user&#39;s motion or voice speech, determine a response based on the acquired intention information, and perform an operation. 
     &lt;AI+Autonomous-Driving/Self-Driving&gt; 
     The autonomous vehicle  100   b  may be implemented as a mobile robot, a vehicle, an unmanned aerial vehicle, etc., to which AI technology is applied. 
     The autonomous vehicle  100   b  may include an autonomous driving control module for controlling the autonomous driving function, and the autonomous driving control module may refer to a software module and/or a chip implementing the software module. The autonomous driving control module may be included in the autonomous vehicle  100   b  as a component of the autonomous vehicle  100   b,  but may be connected to the outside of the autonomous vehicle  100   b  with separate hardware. 
     The autonomous vehicle  100   b  may acquire the state information of the autonomous vehicle  100   b  using the sensor information acquired from various kinds of sensors and/or detect (recognize) the surrounding environment and/or the object, and/or generate map data, and/or determine a travel route and/or a travel plan, and/or determine an operation. 
     Like the robot  100   a,  the autonomous vehicle  100   b  can use the sensor information acquired from at least one sensor among the LIDAR, the radar, and/or the camera to determine the travel route and/or the travel plan. 
     In particular, the autonomous vehicle  100   b  can recognize an environment and/or an object for an area in which the field of view is obscured and/or over a certain distance by receiving sensor information from external devices, and/or receive the recognized information directly from external devices. 
     The autonomous vehicle  100   b  can perform the above-described operations using a learning model composed of at least one ANN. For example, the autonomous vehicle  100   b  can recognize the surrounding environment and/or the object using the learning model, and can determine the travel route using the recognized surrounding information and/or the object information. The learning model may be learned directly from the autonomous vehicle  100   b  and/or learned from an external device such as the AI server  200 . 
     In this case, the autonomous vehicle  100   b  may perform an operation by generating a result using a direct learning model, but the autonomous vehicle may also perform operation by transmitting sensor information to an external device such as the AI server  200  and receiving the generated result. 
     The autonomous vehicle  100   b  may determine the travel route and/or the travel plan using at least one of the map data, the object information detected from the sensor information and/or the object information acquired from the external device, and drive the autonomous vehicle  100   b  according to the determined travel route and/or travel plan by controlling the driving unit. 
     The map data may include object identification information on various objects arranged in a space (e.g. road) in which the autonomous vehicle  100   b  moves. For example, the map data may include object identification information on fixed objects such as street lamps, rocks, and buildings, and/or on movable objects such as vehicles and pedestrians. The object identification information may include a name, a type, a distance, and/or a position, etc. 
     Also, the autonomous vehicle  100   b  may perform the operation and/or run by controlling the driving unit based on the control/interaction of the user. The autonomous vehicle  100   b  may acquire the intention information of the interaction due to the user&#39;s operation and/or voice utterance, determine the response based on the acquired intention information, and perform the operation. 
     &lt;AI+XR&gt; 
     The XR device  100   c  may be implemented as a HMD, a HUD, a TV, a mobile phone, a smartphone, a computer, a wearable device, a home appliance, a digital signage, a vehicle, a fixed robot, a mobile robot, etc., to which AI technology is applied. 
     The XR device  100   c  analyzes the three-dimensional point cloud data and/or image data acquired from various sensors and/or from an external device to generate position data and/or attribute data for the three-dimensional points, thereby obtaining information about the surrounding space and/or the real object, and outputting the rendered XR object. For example, the XR device  100   c  may output an XR object, which includes the additional information about the recognized object, by corresponding to the recognized object. 
     The XR device  100   c  can perform the above-described operations using a learning model composed of at least one ANN. For example, the XR device  100   c  can recognize a real object from three-dimensional point cloud data and/or image data using the learning model, and can provide information corresponding to the recognized real object. The learning model may be learned directly from the XR device  100   c  and/or learned from an external device such as the AI server  1200 . 
     In this case, the XR device  100   c  may perform an operation by generating a result using a direct learning model, but the autonomous vehicle may also perform operation by transmitting sensor information to an external device such as the AI server  200  and receiving the generated result. 
     &lt;AI+Robot+Autonomous-Driving/Self-Driving&gt; 
     The robot  100   a  may be implemented as a guide robot, a carrying robot, a cleaning robot, a wearable robot, an entertainment robot, a pet robot, an unmanned flying robot, etc., to which AI technology and autonomous-driving technology are applied. 
     The robot  100   a,  to which the AI technology and the autonomous-driving technology are applied, may mean the robot  100   a  having the autonomous-driving function itself and/or the robot  100   a  interacting with the autonomous vehicle  100   b.    
     The robot  100   a  having an autonomous-driving function can collectively refer to devices that move by themselves in accordance with a given travel route and/or move by determining the traveling route by themselves without user&#39;s control. 
     The robot  100   a  having the autonomous-driving function and the autonomous vehicle  100   b  can use a common sensing method to determine at least one of the travel route and/or the travel plan. For example, the robot  100   a  having the autonomous-driving function and the autonomous vehicle  100   b  can determine at least one of the travel route and/or the travel plan using the information sensed through the LIDAR, the radar, and/or the camera. 
     The robot  100   a  interacting with the autonomous vehicle  100   b  may exist separately from the autonomous vehicle  100   b,  and the robot  100   a  interacting with the autonomous vehicle  100   b  may be associated with the autonomous-driving function inside and/or outside the autonomous vehicle  100 , and/or may perform an operation associated with the user aboard the autonomous vehicle  100   b.    
     The robot  100   a  interacting with the autonomous vehicle  100   b  may acquire the sensor information on behalf of the autonomous vehicle  100   b  and provide it to the autonomous vehicle  100   b,  or the robot  100   a  interacting with the autonomous vehicle  100   b  may obtain the sensor information and generate the environment information and/or the object information to provide the autonomous vehicle  100   b,  thereby controlling and/or assisting the autonomous-driving function of the autonomous vehicle  100   b.    
     Or, the robot  100   a  interacting with the autonomous vehicle  100   b  may monitor the user boarding the autonomous vehicle  100   b  and/or may control the functions of the autonomous vehicle  100   b  through interaction with the user. For example, when it is determined that the driver is in a drowsy state, the robot  100   a  may activate the autonomous-driving function of the autonomous vehicle  100   b  and/or assist the control of the driving unit of the autonomous vehicle  100   b.  The function of the autonomous vehicle  100   b  controlled by the robot  100   a  may include not only an autonomous-driving function but also a function provided by a navigation system and/or an audio system provided in the autonomous vehicle  100   b.    
     Or, the robot  100   a  interacting with the autonomous vehicle  100   b  may provide information and/or assist the function to the autonomous vehicle  100   b  outside the autonomous vehicle  100   b.  For example, the robot  100   a,  such as a smart traffic light, may provide traffic information including signal information, etc., to the autonomous vehicle  100   b.  The robot  100   a,  such as an automatic electric charger of an electric vehicle, may interact with the autonomous vehicle  100   b  to connect the electric charger to the charging hole automatically. 
     &lt;AI+Robot+XR&gt; 
     The robot  100   a  may be implemented as a guide robot, a carrying robot, a cleaning robot, a wearable robot, an entertainment robot, a pet robot, an unmanned flying robot, a drone, etc., to which AI technology and XR technology are applied. 
     The robot  100   a  to which the XR technology is applied may refer to a robot that is subject to control/interaction in the XR image. In this case, the robot  100   a  may be separated from the XR device  100   c  and can be associated with each other. 
     When the robot  100   a  that is the subject to control/interaction in the XR image acquires the sensor information from the sensors including the camera, the robot  100   a  and/or the XR device  100   c  may generate an XR image based on the sensor information and the XR device  100   c  can output the generated XR image. The robot  100   a  can operate based on a control signal and/or a user&#39;s interaction input through the XR device  100   c.    
     For example, the user can acknowledge the XR image corresponding to the viewpoint of the robot  100   a  remotely linked through the external device such as the XR device  100   c,  and can adjust the autonomous travel path of the robot  100   a,  control operation and/or driving, or check the information of neighboring objects, through interaction. 
     &lt;AI+Autonomous-Driving/Self-Driving+XR&gt; 
     The autonomous vehicle  100   b  may be implemented as a mobile robot, a vehicle, an unmanned aerial vehicle, etc., to which AI technology and XR technology are applied. 
     The autonomous driving vehicle  100   b  to which the XR technology is applied may mean an autonomous vehicle having means for providing an XR image and/or an autonomous vehicle that is subject to control/interaction in the XR image. Particularly, the autonomous vehicle  100   b  that is subject to control/interaction in the XR image may be separated from the XR device  100   c  and can be associated with each other. 
     The autonomous vehicle  100   b  having the means for providing the XR image can acquire the sensor information from the sensors including the camera and output the generated XR image based on the acquired sensor information. For example, the autonomous vehicle  100   b  may include an HUD to output an XR image, thereby providing a passenger with a real object and/or an XR object corresponding to an object in the screen. 
     At this time, when the XR object is output to the HUD, at least a part of the XR object may be output so as to overlap with the actual object that the passenger&#39;s gaze is directed to. On the other hand, when the XR object is output to the display provided in the autonomous vehicle  100   b,  at least a part of the XR object may be output so as to overlap with the object in the screen. For example, the autonomous vehicle  100   b  can output XR objects corresponding to objects such as a lane, another vehicle, a traffic light, a traffic sign, a two-wheeled vehicle, a pedestrian, a building, etc. 
     When the autonomous vehicle  100   b  that is the subject to control/interaction in the XR image acquires the sensor information from the sensors including the camera, the autonomous vehicle  100   b  and/or the XR device  100   c  may generate an XR image based on the sensor information and the XR device  100   c  can output the generated XR image. The autonomous vehicle  100   b  can operate based on a control signal and/or a user&#39;s interaction input through the XR device  100   c.    
     In the above, embodiments have been exemplarily described, but the disclosure of the present specification is not limited to such specific embodiments, and thus, modifications, changes, or can be improved. 
     In the exemplary system described above, the methods are described on the basis of a flowchart as a series of steps or blocks, however, the present specification is not limited to the order of the steps, and some steps may occur in a different order or concurrently with other steps as described above. In addition, those skilled in the art will understand that the steps shown in the flowchart are not exhaustive and that other steps may be included or that one or more steps of the flowchart may be deleted without affecting the scope of the present specification. 
     The claims described herein may be combined in various ways. For example, the technical features of the method claims of the present specification may be combined and implemented as an apparatus, and the technical features of the apparatus claims of the present specification may be combined and implemented as a method. In addition, the technical features of the method claim of the present specification and the technical features of the apparatus claim may be combined to be implemented as an apparatus, and the technical features of the method claim of the present specification and the technical features of the apparatus claim may be combined and implemented as a method.