Client devices and network nodes for efficient disaster recovery

Abstract

This disclosure relates to a client device (100) for efficient disaster handling based on a new list of PLMNs for disaster states. The client device (100) has a list of PLMNs available to it in the event that its serving PLMN (610) enters a disaster state. Upon determining that the serving PLMN (610) is in a disaster state, the client device (100) registers with the visited PLMN in the list. The new list of PLMNs for disaster states enables the client device (100) to roam into PLMNs that might be prohibited under normal conditions.

Description

Technical Field

[0001] This disclosure relates to a client device and network node for efficient disaster recovery. Furthermore, this disclosure also relates to corresponding methods and computer programs. Background Technology

[0002] During disasters, cellular networks are often overloaded, and users may experience a denial of service. Disasters can be man-made, such as a fire in a building, or natural, such as an earthquake. When a disaster occurs, many people may try to call emergency services or contact each other. As multiple users request service simultaneously, network resources may become congested, and users may be unable to obtain the service they requested. Summary of the Invention

[0003] The purpose of this disclosure is to provide a solution that reduces or solves the drawbacks and problems of conventional solutions.

[0004] The foregoing and other objectives are achieved through the subject matter of the independent claims. Other advantageous embodiments of this disclosure can be found in the dependent claims.

[0005] According to a first aspect of this disclosure, the above and other objectives are achieved through a client device for a communication system, said client device being served by a public land mobile network (PLMN), and also used for...

[0006] Obtain a list of PLMNs that include one or more visiting PLMNs; and

[0007] When it is determined that the service PLMN is in a disaster state, the visited PLMN in the PLMN list is registered.

[0008] A serving PLMN can be understood as the PLMN currently serving the client device, that is, providing communication services to the client device. The serving PLMN can be the home PLMN, which typically occurs when the client device is in its home country. The serving PLMN can also be a PLMN different from the home PLMN, for example, when the client device is roaming in different countries.

[0009] A visited PLMN can be understood as a PLMN that the client device can attempt to register in a disaster state. A visited PLMN can also be a PLMN that the client device is not allowed to register in normal circumstances, such as a disabled PLMN, for example, a PLMN configured in the disabled PLMN list in the client device 100. Each visited PLMN can be indicated by an identifier and can also be associated with a timer that defines the minimum waiting time before registration.

[0010] A disaster state can be understood as a state that the government decides when to initiate and terminate, and can be caused by man-made or natural disasters. When a disaster state occurs, users may have the opportunity to reduce service interruptions and failures.

[0011] According to the first aspect, the advantage of the client device is that it possesses information about the PLMN that can be used during a disaster, even before the disaster occurs. In the event of a disaster affecting the service PLMN, the client device therefore knows which PLMN to use and can quickly attempt to register for that PLMN. Thus, service interruption is minimized during a disaster.

[0012] According to the first aspect, in the implementation of the client device, obtaining the PLMN list includes:

[0013] Receive a first control message from a network node, wherein the first control message indicates the PLMN list.

[0014] The advantage of this implementation is that the network node can provide the client device with information about the PLMN to be used in a disaster situation even before the disaster occurs. Therefore, the network node can control the behavior of its client devices to cope with possible future disaster situations.

[0015] According to the first aspect, in the implementation of the client device, the first control message is part of a non-access stratum (NAS) protocol.

[0016] The advantage of this implementation is that it can use standard protocols already used for communication between the network node and the client device, which simplifies implementation.

[0017] According to the first aspect, in the implementation of the client device, the first control message is any one of the following: configuration update command message, registration accept message, registration reject message, service accept message, service reject message, and deregistration request message.

[0018] The advantage of this implementation is that it can use standard messages already used for communication between the network node and the client device, which simplifies the implementation. Furthermore, the PLMN list can be dynamically changed through any of these messages.

[0019] According to the first aspect, in the implementation of the client device, obtaining the PLMN list includes:

[0020] The PLMN list is obtained from the subscriber identity module (SIM) configuration of the client device.

[0021] The advantage of this implementation is that the PLMN list can be pre-configured in the SIM of the client device. Therefore, it is not necessary to transmit the PLMN list to the client device via signaling, and wireless resources can be saved.

[0022] According to the first aspect, in the implementation of the client device, obtaining the PLMN list includes:

[0023] The PLMN list is obtained from the mobile equipment (ME) configuration of the client device.

[0024] The advantage of this implementation is that the PLMN list can be pre-configured in the client device. Therefore, it is not necessary to transmit the PLMN list to the client device via signaling, and wireless resources can be saved.

[0025] According to the first aspect, in the implementation of the client device, the PLMN list includes the identifier of each visited PLMN in the PLMN list.

[0026] The advantage of this implementation is that it provides a simple method for the client device to identify the PLMN.

[0027] According to the first aspect, in the implementation of the client device, the PLMN list includes one or more timers, wherein each timer is associated with a visited PLMN in the PLMN list and defines a start registration time instance for the visited PLMN and / or a re-registration time instance for the service PLMN.

[0028] The timer defining the start registration time instance can also be understood as a timer defining the minimum waiting time before registration begins. Similarly, the timer defining the re-registration time instance can be understood as a timer defining the minimum waiting time before re-registration begins. The minimum waiting time can be understood as the shortest time the client device waits before attempting to register or re-register.

[0029] The advantage of this implementation is that the PLMN list also includes timer information indicating when the client device can attempt to register with a visited PLMN in the list. Using this timer information, the registration attempts of the client device can be controlled, preventing the client device from simultaneously attempting to register with the PLMN, thereby preventing overload within the PLMN.

[0030] According to the first aspect, in an implementation of the client device, the client device is further configured to:

[0031] While residing at the visited PLMN, start a timer associated with the visited PLMN; and

[0032] When the timer associated with the visited PLMN expires, register with the visited PLMN.

[0033] Here, "when the timer expires" can be understood as either when the timer expires or after the timer expires.

[0034] The advantage of this implementation is that the registration time of the client devices can be controlled by the PLMN list. Therefore, the PLMN list can be used to assign client device registration attempts to specific PLMNs over time, thereby preventing the PLMNs from becoming overloaded during disaster situations.

[0035] According to the first aspect, in the implementation of the client device, one or more visited PLMNs in the PLMN list are arranged in order of registration priority of the client device.

[0036] This can be understood as meaning that, in certain circumstances, the client device should follow the order of the visited PLMNs in the PLMN list when attempting to register with a visited PLMN in the PLMN list.

[0037] The advantage of this implementation is that the PLMN list clearly indicates to the client device which PLMN it should attempt to register with in the event of a disaster. Therefore, the PLMN list can be used to assign client devices to different visited PLMNs.

[0038] According to the first aspect, in the implementation of the client device, determining that the service PLMN is in the disaster state includes:

[0039] Receive a second control message from a network node, wherein the second control message indicates that the service PLMN is in the disaster state.

[0040] The advantage of this implementation is that the client device will know when to start searching for other PLMNs based on the indication of a disaster state.

[0041] According to the first aspect, in an implementation of the client device, the client device is further configured to:

[0042] The system provides output to the user of the client device, wherein the output indicates that when the service PLMN is in the disaster state, one or more visited PLMNs in the PLMN list can be selected for roaming.

[0043] The advantage of this implementation is that it presents the user with information that allows them to select the appropriate PLMN in the event of a disaster.

[0044] According to the first aspect, in the implementation of the client device, the registration of the visited PLMN in the PLMN list includes:

[0045] Send a registration request message to the visited PLMN, wherein the registration request message indicates a registration request for the client device when the client device's previous serving PLMN is in the disaster state.

[0046] The advantage of this implementation is that the visited PLMN knows that the client device is attempting to register with this PLMN because the client device must leave another PLMN due to a disaster. This can help the visited PLMN to apply less stringent authentication to the client device, for example, considering that the client device is only seeking temporary services from the PLMN.

[0047] According to a second aspect of this disclosure, the above and other objectives are achieved through a network node for a wireless communication system, said network node being configured to:

[0048] A control message is sent to the client device, wherein the control message indicates a list of PLMNs, the list of PLMNs including one or more visited PLMNs that the client device can register with when the client device's serving PLMN is in a disaster state.

[0049] The network node can be associated with the service PLMN of the client device, which can be understood as the network node being part of the service PLMN.

[0050] According to the second aspect, the advantage of the network node is that it can provide the client devices with information about the PLMN to be used in a disaster situation even before a disaster occurs. Therefore, the network node can control the behavior of its client devices to cope with potential future disaster situations.

[0051] According to the second aspect, in the implementation of the network node, the network node is the access and mobility management function (AMF) of the core network.

[0052] The advantage of this implementation is that the AMF can provide the client devices with information about the PLMN to be used in a disaster situation even before the disaster occurs. Therefore, the AMF can control the behavior of its client devices to cope with possible future disaster situations.

[0053] According to the second aspect, in the implementation of the network node, the control message is part of the NAS protocol.

[0054] The advantage of this implementation is that it can use standard protocols already used for communication between the network node and the client device, which simplifies implementation.

[0055] According to the second aspect, in the implementation of the network node, the control message is any one of the following: configuration update command message, registration accept message, registration reject message, service accept message, service reject message, and deregistration request message.

[0056] The advantage of this implementation is that it can use standard messages already used for communication between the network node and the client device, which simplifies the implementation. Furthermore, the PLMN list can be dynamically changed through any of these messages.

[0057] According to a third aspect of this disclosure, the above and other objectives are achieved through a method for a client device to be served by a PLMN service, the method comprising:

[0058] Obtain a list of PLMNs that include one or more visited PLMNs; and

[0059] When it is determined that the service PLMN is in a disaster state, the visited PLMN in the PLMN list is registered.

[0060] The method according to the third aspect can be extended to an implementation corresponding to the implementation of the client device according to the first aspect. Therefore, the implementation of the method includes one or more features of the corresponding implementation of the client device.

[0061] The advantages of the method according to the third aspect are the same as the advantages of the corresponding implementation of the client device according to the first aspect.

[0062] According to a fourth aspect of this disclosure, the above and other objectives are achieved through a method for network nodes, the method comprising:

[0063] A control message is sent to the client device, wherein the control message indicates a list of PLMNs, the list of PLMNs including one or more visited PLMNs that the client device can register with when the client device's serving PLMN is in a disaster state.

[0064] The method according to the fourth aspect can be extended to an implementation corresponding to the implementation of the network node according to the second aspect. Therefore, the implementation of the method includes one or more features of the corresponding implementation of the network node.

[0065] The advantages of the method according to the fourth aspect are the same as the advantages of the corresponding implementation of the network node according to the second aspect.

[0066] This disclosure also relates to a computer program characterized by program code that, when run by at least one processor, causes the at least one processor to perform any method according to embodiments of this disclosure. Furthermore, this disclosure relates to a computer program product comprising a computer-readable medium and the computer program therein, wherein the computer program is contained in the computer-readable medium and includes one or more of the group consisting of: read-only memory (ROM), programmable ROM (PROM), erasable PROM (EPROM), flash memory, electrically EPROM (EEPROM), and hard disk drive.

[0067] Other applications and advantages of embodiments of this disclosure will become apparent from the following detailed description. Attached Figure Description

[0068] The accompanying drawings are intended to illustrate and explain different embodiments of this disclosure, in which:

[0069] - Figure 1 A client device according to an embodiment of this disclosure is shown;

[0070] - Figure 2 A method for a client device according to an embodiment of this disclosure is shown;

[0071] - Figure 3 A network node according to an embodiment of this disclosure is shown;

[0072] - Figure 4 A method for a network node according to an embodiment of this disclosure is shown;

[0073] - Figure 5 A communication system according to an embodiment of the present disclosure is shown;

[0074] - Figure 6 A flowchart of a method for a client device according to an embodiment of the present disclosure is shown;

[0075] - Figure 7 The signaling from a network node according to an embodiment of this disclosure is illustrated. Detailed Implementation

[0076] If a public land mobile network (PLMN) is unable to provide services such as voice calls or mobile data to user equipment (UE) due to a disaster, there are usually other PLMNs in the area that may be able to provide services to the UE. However, those PLMNs can be configured as disabled PLMNs in the UE, so the UE will never select one of those PLMNs.

[0077] To minimize service disruption, it is beneficial for a UE in a given PLMN to be able to obtain service from another PLMN in the area where a disaster occurs, even if that other PLMN is a disabled PLMN for the UE under normal conditions. PLMN selection is a process within the UE that allows the UE to select the most suitable PLMN at a given point in time. Most of the time, when the UE is in its home country, the home PLMN will be the most suitable PLMN and therefore the serving PLMN. To prevent the UE from switching from the home PLMN, roaming is typically disabled within the home country. For example, other PLMNs in the home country can be added to the disabled PLMN list so that the UE does not needlessly roam into these PLMNs.

[0078] This disclosure provides an improved PLMN selection method for a UE during a disaster. The UE has a list of PLMNs available to the UE when its serving PLMN is in a disaster state. With the help of the list of PLMNs for disaster states, the UE can roam into or even disable PLMNs during a disaster state.

[0079] Figure 1 A client device 100 according to an embodiment of this disclosure is shown. Figure 1 In the illustrated embodiment, client device 100 includes a processor 102, a transceiver 104, and a memory 106. The processor 102 is coupled to the transceiver 104 and the memory 106 via a communication component 108 known in the art. Client device 100 also includes an antenna or antenna array 110 coupled to the transceiver 104, meaning that client device 100 is used for wireless communication in a wireless communication system.

[0080] In this disclosure, the client device 100 being used to perform certain actions can be understood to mean that the client device 100 includes appropriate components for performing said actions, such as processor 102 and transceiver 104.

[0081] According to an embodiment of this disclosure, client device 100 is used to be served by service PLMN 610, and is also used to obtain a list of PLMNs including one or more visited PLMNs 620a, 620b, ..., 620n. Client device 100 is also used to register with the visited PLMNs in the PLMN list when it is determined that service PLMN 610 is in a disaster state.

[0082] Figure 2 A flowchart of the corresponding method 200 is shown, which can be implemented on a client device 100, for example... Figure 1 The method shown is executed on a client device served by service PLMN 610. Method 200 includes 202: obtaining a list of PLMNs including one or more visited PLMNs 620a, 620b, ..., 620n. Method 200 also includes 204: registering the visited PLMNs in the PLMN list when it is determined that service PLMN 610 is in a disaster state.

[0083] Figure 3 A network node 300 according to an embodiment of this disclosure is shown. Figure 3 In the illustrated embodiment, network node 300 includes a processor 302, a transceiver 304, and a memory 306. The processor 302 is coupled to the transceiver 304 and the memory 306 via a communication component 308 known in the art. Network node 300 can be used for wireless and wired communication in wireless and wired communication systems, respectively. Wireless communication capability is provided via an antenna or antenna array 310 coupled to the transceiver 304, while wired communication capability is provided via a wired communication interface 312 coupled to the transceiver 304.

[0084] In this disclosure, the network node 300 performing certain actions can be understood to mean that the network node 300 includes appropriate components for performing said actions, such as processor 302 and transceiver 304.

[0085] According to an embodiment of this disclosure, network node 300 is used to send control message 510 to client device 100. Control message 510 indicates a PLMN list, the PLMN list including one or more visited PLMNs 620a, 620b, ..., 620n that the client device 100 can register when its serving PLMN 610 is in a disaster state.

[0086] Figure 4 This shows that it can be done at network node 300, such as Figure 3 The flowchart illustrates the corresponding method 400 executed in the network node. Method 400 includes 402: sending a control message 510 to the client device 100. The control message 510 indicates a PLMN list, which includes one or more visited PLMNs 620a, 620b, ..., 620n that the client device 100 can register with when its serving PLMN 610 is in a disaster state.

[0087] Figure 5 A communication system 500 according to an embodiment of the present disclosure is illustrated. The communication system 500 includes a client device 100 and a plurality of PLMNs 610, 620a, 620b that at least partially overlap each other. The client device 100 is served by a serving PLMN 610. The serving PLMN 610 can be a home PLMN or a visited PLMN. In the home country of the client device 100, the serving PLMN 610 is typically the home PLMN of the client device 100. When the client device 100 roams in another country, the serving PLMN 610 is typically a visited PLMN.

[0088] Several additional PLMNs may at least partially cover the same area as the serving PLMN 610, and these additional PLMNs are herein referred to as one or more visited PLMNs 620a, 620b, ..., 620n. Figure 5 In the illustrated embodiment, the first visited PLMN 620a and the second visited PLMN 620b cover the area where the client device 100 is located.

[0089] According to an embodiment of this disclosure, client device 100 obtains a list of PLMNs available to client device 100 in the event that service PLMN 610 is in a disaster state (i.e., a disaster occurs affecting service PLMN 610). The PLMN list includes one or more visited PLMNs 620a, 620b, ..., 620n, and when it is determined that service PLMN 610 is in a disaster state, client device 100 can register with one of the visited PLMNs in the PLMN list. Each visited PLMN 620n can be associated with a timer that defines when client device 100 can attempt to register with visited PLMN 620n, for example, defining a minimum waiting time before registration. Furthermore, one or more visited PLMNs 620a, 620b, ..., 620n can be arranged in the PLMN list according to registration priority. Therefore, the client device 100 can select the visited PLMN 620n from the PLMN list according to the order in which the visited PLMNs are arranged in the PLMN list, and further register with the selected visited PLMN 620n after the timer associated with the visited PLMN 620n expires, as will be referred to below. Figure 6 Further explanation.

[0090] refer to Figure 5 Assume that client device 100 obtains a list of PLMNs including a first visited PLMN 620a and a second visited PLMN 620b. Also assume that serving PLMN 610 enters a disaster state and can no longer provide any communication services to client device 100, while the first visited PLMN 620a and / or the second visited PLMN 620b are functioning normally, i.e., not in a disaster state. In this case, when client device 100 determines that serving PLMN 610 is in a disaster state, the PLMN list allows client device 100 to register with either the first visited PLMN 620a or the second visited PLMN 620b, as further described below. Therefore, during a disaster, service interruption for client device 100 can be minimized.

[0091] Figure 6 A flowchart of a method 600 according to an embodiment of the present disclosure is shown. Method 600 can be executed by the client device 100 when the client device 100 is served by the service PLMN 610.

[0092] In step 602, client device 100 obtains a list of PLMNs including one or more visited PLMNs 620a, 620b, ..., 620n. Obtaining the PLMN list may include client device 100 receiving a first control message 510 from network node 300, wherein the first control message 510 indicates the PLMN list. Network node 300 may be associated with a serving PLMN 610, which can be understood as meaning that network node 300 is part of the serving PLMN 610, such as a core network function in the serving PLMN 610. The PLMN list may be explicitly indicated in the control message 510, for example, as a new or updated information element (IE) included in the control message 510. In an embodiment, the first control message 510 is part of a non-access stratum (NAS) protocol. The first control message 510 may be, for example, any of a configuration update command message, a registration accept message, a registration reject message, a service accept message, a service reject message, and a deregistration request message.

[0093] Obtaining the PLMN list may also include the client device 100 obtaining the PLMN list from at least one of the client device 100's subscriber identity module (SIM) configuration and the client device 100's mobile equipment (ME) configuration. The PLMN list may, for example, be pre-configured in the SIM and / or stored in the ME.

[0094] The obtained PLMN list may include an identifier for each visited PLMN 620n in the list. The identifier of the visited PLMN 620n enables the client device 100 to detect and register with the visited PLMN 620n. The PLMN list may also include one or more timers T1, T2, ..., Tn, where each timer Tn is associated with a visited PLMN 620n in the PLMN list and defines a start registration time instance and / or a re-registration time instance at the visited PLMN 620n and / or the service PLMN 610. Timer Tn may define the minimum waiting time before starting registration and / or re-registration, i.e., the shortest time the client device 100 waits before attempting to register with the visited PLMN 620n or re-register with the previously service PLMN 610. In this way, the time instances for client device 100's registration and / or re-registration can be controlled based on the visited PLMN 620n. However, a single timer for all or one visited PLMNs 620a, 620b, ..., 620n in the PLMN list can also be used without departing from the scope of this disclosure. Therefore, in an embodiment, client device 100 can register all visited PLMNs and / or re-register a previously served PLMN 610 using the same minimum waiting time.

[0095] The value of timer Tn can be based on the characteristics of client device 100 and / or users, such as user priority. For example, a high-priority user's client device may obtain a list of PLMNs where the timer Tn value for each visited PLMN 620n is lower than that of a normal or low-priority user's client device. In this way, a high-priority user's client device may attempt to register with the visited PLMN 620n earlier than a normal or low-priority user's client device.

[0096] In this embodiment, one or more visited PLMNs 620a, 620b, ..., 620n in the PLMN list are arranged in order of registration priority of the client device 100. Therefore, each visited PLMN 620n in the PLMN list can be associated with a registration priority, and arranged, for example, with the visited PLMN 620n having the highest registration priority being first in the PLMN list. When the client device 100 determines to register a visited PLMN 620n in the PLMN list, the client device 100 can select a visited PLMN 620n from the PLMN list according to the registration priority order, and for example, first attempt to register the visited PLMN ranked first in the PLMN list.

[0097] In step 604, client device 100 determines that serving PLMN 610 is in a disaster state. Client device 100 can determine this based on an indication from serving PLMN 610 or another PLMN. In an embodiment, determining that serving PLMN 610 is in a disaster state may include client device 100 receiving a second control message 520 from network node 300', wherein the second control message 520 indicates that serving PLMN 610 is in a disaster state. The network node 300' sending the second control message 520 may be the same as or different from the network node 300 that sent the first control message 510. Network node 300' may be, for example, a base station of a radio access network (RAN) or a core network function in serving PLMN 610 or another PLMN.

[0098] The second control message 520 may be, for example, a system information block (SIB) broadcast by network node 300'. If the serving PLMN 610 does not respond, the client device 100 may read the SIB broadcast from another PLMN and obtain from there an indication that the serving PLMN 610 is in a disaster state.

[0099] When it is determined in step 604 that the service PLMN 610 is in a disaster state, the client device 100 registers with the visited PLMN 620n in the PLMN list in step 606. Step 606 may include the client device 100 residing on the visited PLMN 620n selected from the PLMN list and sending a registration request to the visited PLMN.

[0100] Before attempting to register a visited PLMN 620n in the PLMN list, client device 100 may fail to perform a conventional PLMN selection. Client device 100 may, for example, have scanned for available PLMNs and found only disabled PLMNs, or found non-disabled PLMNs but be unable to register them. Client device 100 then performs step 606 and registers the visited PLMN in the PLMN list.

[0101] To indicate that registration is associated with a disaster state, client device 100 can indicate this to the visited PLMN 620n in the registration request. This allows the visited PLMN 620n to treat client device 100 specially. For example, when client device 100 is only seeking temporary service from the visited PLMN 620n, the visited PLMN 620n can dilute the authentication requirements. Therefore, step 606 in an embodiment may include client device 100 sending a registration request message to the visited PLMN 620n, wherein the registration request message indicates a registration request for client device 100 when the client device 100's previous service PLMN 610 is in a disaster state.

[0102] Client device 100 can automatically select the visited PLMN 620n from the PLMN list, or the visited PLMN 620n can be manually selected by the user of client device 100. For example, client device 100 can operate in automatic mode where client device 100 automatically selects the PLMN, or in manual mode where the user is responsible for selecting the PLMN from the PLMN list presented to the user.

[0103] When client device 100 operates in automatic mode, it automatically selects a visited PLMN 620n from the PLMN list when it determines that service PLMN 610 is in a disaster state. In a disaster state, the selection may involve a PLMN list and a PLMN selection process. The PLMN selection process may, for example, define that visited PLMNs should be selected from the PLMN list in the order they are listed. Therefore, client device 100 can select the first visited PLMN from the PLMN list and attempt to register with it. If registration fails, client device 100 can select and attempt to register with the next visited PLMN in the PLMN list.

[0104] When the PLMN list includes a timer Tn associated with the selected visited PLMN 620n, the client device 100 can start the timer Tn associated with the visited PLMN 620n while residing in the visited PLMN 620n, and register with the visited PLMN 620n when the timer Tn associated with the visited PLMN 620n expires. The timer defines a start registration time instance. The client device 100 can register with the visited PLMN 620n either when the timer expires or after the timer Tn expires; that is, the client device 100 can register at any time once the timer expires. Therefore, the timer Tn can define a minimum waiting time, i.e., the shortest time the client device 100 waits before attempting to register with the visited PLMN 620n. In this way, the registration of the client device with the visited PLMN 620n due to a disaster state in the serving PLMN 610 can be controlled in time according to the PLMN list.

[0105] Timer Tn can also define a re-registration time instance at service PLMN 610 and can be used immediately after the disaster recovery period ends. Similar to registration, timer Tn can define a minimum wait time, which is the shortest time client device 100 must wait before attempting to re-register with service PLMN 610. When it is determined that service PLMN 610 is no longer in a disaster recovery state, client device 100 can re-register with service PLMN 610 after the minimum wait time according to timer Tn. Once client device 100 resides on service PLMN 610, it can wait for timer Tn to perform the registration update process for service PLMN 610. This is to ensure that service PLMN 610 does not become congested when all client devices attempt to recover after a disaster recovery.

[0106] When client device 100 operates in manual mode, it can provide output to its user. This output can indicate that when the serving PLMN 610 is in a disaster state, one or more visited PLMNs 620a, 620b, ..., 620n from the PLMN list can be selected for roaming. Therefore, when the serving PLMN 610 of client device 100 is in a disaster state, and the user of client device 100 initiates manual PLMN selection, the output according to this disclosure can be presented to the user. Thus, the user receives an indication that one or more visited PLMNs 620a, 620b, ..., 620n support disaster roaming and are available for safe selection by the user (even if the visited PLMN is a disabled PLMN in normal operation).

[0107] Figure 7The illustration shows signal transmission from network node 300 according to an embodiment of this disclosure, wherein network node 300 provides a list of PLMNs to client device 100. Network node 300 may be, for example, an access and mobility management function (AMF) serving the core network in PLMN 610.

[0108] refer to Figure 7 Network node 300 sends control message 510 to client device 100. Control message 510 indicates a PLMN list, which includes one or more visited PLMNs 620a, 620b, ..., 620n that the client device 100 can register with when its serving PLMN 610 is in a disaster state. Control message 510 may be part of a NAS protocol. Control message 510 may be, for example, any of a configuration update command message, registration accept message, registration reject message, service accept message, service reject message, and deregistration request message. For example, control message 510 may be a new or updated information element (IE) in any of the above messages.

[0109] As previously mentioned, each visited PLMN 620n in the PLMN list can be associated with an identifier and / or a timer Tn. Using the value of timer Tn, network node 300 can control when client device 100 attempts to register with a visited PLMN 620n in the PLMN list during a disaster. By providing different timer Tn values ​​for different client devices for the same visited PLMN 620n, registration attempts with the visited PLMN 620n can be distributed over time, preventing overload of the visited PLMN 620n when the serving PLMN 610 enters a disaster state.

[0110] Furthermore, one or more visited PLMNs 620a, 620b, ..., 620n in the PLMN list can be arranged according to the registration priority order of client devices 100. By providing different registration priority orders to different client devices, client devices can be distributed across one or more visited PLMNs 620a, 620b, ..., 620n in the PLMN list, ensuring that a single visited PLMN 620n will not be overloaded when the service PLMN 610 enters a disaster state. For example, if PLMN B and PLMNC support disaster roaming from PLMN A, PLMN A can configure a first client device to have PLMN lists (PLMNB, PLMN C) and a second client device to have PLMN lists (PLMN C, PLMN B), so that in the event of a disaster state in PLMN A, the first client device will go to PLMN B, and the second client device will go to PLMN C.

[0111] If the service PLMN 610 enters a disaster state, the network node 300 can send a second control message 520 to the client device 100 indicating that the service PLMN 610 is in a disaster state, such as... Figure 7 As shown. In this embodiment, the second control message 520 can be sent by another network node 300' in the serving PLMN 610 or another PLMN, that is, the first control message 510 and the second control message 520 can be sent to the client device 100 from different network nodes in this embodiment.

[0112] In this document, client device 100 can refer to a user device, user equipment (UE), mobile station, Internet of Things (IoT) device, sensor device, wireless terminal, and / or mobile terminal capable of wireless communication in a wireless communication system (sometimes also called a cellular wireless system). UE can also be referred to as a wirelessly capable mobile phone, cellular phone, computer tablet, or portable computer. For example, in this context, UE can be a portable, pocket-sized, handheld, computer-based, or vehicle-mounted mobile device capable of transmitting voice and / or data with another entity (e.g., another receiver or server) via a wireless access network. UE can be a station (STA), i.e., any device containing IEEE 802.11-compliant media access control (MAC) and physical layer (PHY) interfaces connected to the wireless medium (WM). UE can also be used for communication in 3GPP-related LTE and LTE-Advanced, in WiMAX and its evolutions, and in fifth-generation wireless technologies (e.g., New Radio).

[0113] In this paper, network nodes 300 and 300' can represent the access and mobility management function (AMF) of the core network as defined by the 3GPP standard. The AMF can be a function used for communication in 3GPP fifth-generation radio technologies, such as new radio (NR).

[0114] Furthermore, any method according to embodiments of this disclosure can be implemented in a computer program having code components, which, when run by a processing component, causes the processing component to perform method steps. The computer program is included in a computer-readable medium of the computer program product. The computer-readable medium can substantially include any memory, such as read-only memory (ROM), programmable read-only memory (PROM), erasable PROM (EPROM), flash memory, electrically erasable PROM (EEPROM), or a hard disk drive.

[0115] Furthermore, those skilled in the art recognize that embodiments of the client device 100 and network node 300 include the necessary communication capabilities for executing the scheme, in the form of, for example, functions, components, units, elements, etc. Examples of other such components, units, elements, and functions include: processors, memories, buffers, control logic, encoders, decoders, rate matchers, de-rate matchers, mapping units, multipliers, decision units, selection units, switches, interleavers, deinterleavers, modulators, demodulators, inputs, outputs, antennas, amplifiers, receiving units, transmitting units, digital signal processors (DSPs), management systems divisions (MSDs), trellis coded modulation (TCM) encoders, TCM decoders, power supply units, power feeders, communication interfaces, communication protocols, etc., which are appropriately arranged together to execute the scheme.

[0116] Specifically, one or more processors in the client device 100 and network node 300 may include, for example, a central processing unit (CPU), processing unit, processing circuitry, processor, application-specific integrated circuit (ASIC), microprocessor, or one or more instances of other processing logic capable of interpreting and executing instructions. Therefore, the expression "processor" can refer to a system comprising multiple processing circuits, such as any, some, or all of the aforementioned processing circuits. The processing circuitry system can also perform data processing functions for inputting, outputting, and processing data, including data buffering and device control functions such as call processing control, user interface control, etc.

[0117] Finally, it should be understood that this disclosure is not limited to the embodiments described above, but also relates to and incorporates all embodiments within the scope of the appended independent claims.

Claims

1. A client device (100) for a communication system (500), characterized in that, The client device (100) is used to serve by the Public Land Mobile Network (PLMN) (610), and is also used to: Obtain a list of PLMNs including one or more visited PLMNs (620a, 620b, ..., 620n); as well as When it is determined that the service PLMN (610) is in a disaster state, register the visited PLMN in the PLMN list. The PLMN list includes one or more timers (T1, T2, ..., Tn), wherein each timer (Tn) is associated with a visited PLMN (620n) in the PLMN list and defines the shortest time the client device (100) must wait before attempting to register with the visited PLMN (620n) and / or re-register with the service PLMN (610).

2. The client device (100) according to claim 1, characterized in that, Obtaining the PLMN list includes: Receive a first control message (510) from the network node (300), wherein the first control message (510) indicates the PLMN list.

3. The client device (100) according to claim 2, characterized in that, The first control message (510) is part of the non-access stratum NAS protocol.

4. The client device (100) according to claim 3, characterized in that, The first control message (510) is any one of the following: configuration update command message, registration accept message, registration reject message, service accept message, service reject message, and deregistration request message.

5. The client device (100) according to claim 4, characterized in that, Obtaining the PLMN list includes: The PLMN list is obtained from the SIM configuration of the user identification module of the client device (100).

6. The client device (100) according to claim 4, characterized in that, Obtaining the PLMN list includes: The PLMN list is obtained from the mobile device ME configuration of the client device (100).

7. The client device (100) according to claim 1, characterized in that, The PLMN list includes the identifier of each visited PLMN (620n) in the PLMN list.

8. The client device (100) according to claim 1, characterized in that, Also used for: While residing at the visited PLMN (620n), start the timer (Tn) associated with the visited PLMN (620n); and When the timer (Tn) associated with the visited PLMN (620n) expires, register with the visited PLMN (620n).

9. The client device (100) according to claim 8, characterized in that, The one or more visited PLMNs (620a, 620b, ..., 620n) in the PLMN list are arranged in order of registration priority of the client device (100).

10. The client device (100) according to claim 9, characterized in that, Determining that the service PLMN (610) is in the disaster state includes: Receive a second control message (520) from the network node (300'), wherein the second control message (520) indicates that the service PLMN (610) is in the disaster state.

11. The client device (100) according to claim 10, characterized in that, Also used for: Output is provided to the user (600) of the client device (100), wherein the output indicates that when the service PLMN (610) is in the disaster state, one or more visited PLMNs (620a, 620b, ..., 620n) in the PLMN list are selected for roaming.

12. The client device (100) according to any one of claims 1 to 11, characterized in that, The visited PLMN registration in the PLMN list includes: Send a registration request message to the visited PLMN, wherein the registration request message indicates a registration request for the client device (100) when the client device (100)’s previous serving PLMN (610) is in the disaster state.

13. A network node (300) for a communication system (500), characterized in that, The network node (300) is used for: A first control message (510) is sent to the client device (100), wherein the first control message (510) indicates a list of PLMNs, the list of PLMNs including one or more visited PLMNs (620a, 620b, ..., 620n) for the client device (100) to register when the client device (100)’s service PLMN (610) is in a disaster state, the list of PLMNs including one or more timers (T1, T2, ..., Tn), wherein each timer (Tn) is associated with a visited PLMN (620n) in the list of PLMNs and defines the shortest time the client device (100) must wait before attempting to register with the visited PLMN (620n) and / or re-register with the service PLMN (610).

14. The network node (300) according to claim 13, characterized in that, The network node (300) is the core network's Access and Mobility Management Function (AMF).

15. The network node (300) according to claim 13 or 14, characterized in that, The first control message (510) is part of the NAS protocol.

16. The network node (300) according to claim 15, characterized in that, The first control message (510) is any one of the following: configuration update command message, registration accept message, registration reject message, service accept message, service reject message, and deregistration request message.

17. A method (200) for a client device (100) to be served by a service PLMN (610), characterized in that, The method (200) includes: Obtain (202) a list of PLMNs including one or more visited PLMNs (620a, 620b, ..., 620n); and When it is determined that the service PLMN (610) is in a disaster state, the visited PLMN in the PLMN list is registered (204), the PLMN list including one or more timers (T1, T2, ..., Tn), wherein each timer (Tn) is associated with a visited PLMN (620n) in the PLMN list, and defines the shortest time the client device (100) must wait before attempting to register with the visited PLMN (620n) and / or re-register with the service PLMN (610).

18. A method (400) for a network node (300), characterized in that, The method (400) includes: Send a (402) first control message (510) to the client device (100), wherein the first control message (510) indicates a list of PLMNs, the list of PLMNs including one or more visited PLMNs (620a, 620b, ..., 620n) for the client device (100) to register with when the client device (100)’s service PLMN (610) is in a disaster state, the list of PLMNs including one or more timers (T1, T2, ..., Tn), wherein each timer (Tn) is associated with a visited PLMN (620n) in the list of PLMNs and defines the shortest time the client device (100) must wait before attempting to register with the visited PLMN (620n) and / or re-register with the service PLMN (610).

19. A computer-readable medium, characterized in that, The computer-readable medium includes a computer program having program code for performing the method according to claim 17 or 18 when the computer program is run on a computer.

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