Network registration method in roaming scenario and terminal device

Abstract

The present application relates to the field of communications, and provides a network registration method in a roaming scenario and a terminal device. In the method, if a terminal device fails to register in a first high-standard network (e.g. 4G network) of a PLMN of a first roaming network operator (e.g. China Mobile), when receiving a registration rejection message that instructs searching the PLMN of the first roaming network operator for a second network (e.g. a 3G network or a 2G network) of which the network standard is lower than that of the first network, in response to the registration rejection message, the terminal device searches PLMNs of other roaming network operators in a roaming region for the first high-standard network. Thus, when searching out the first high-standard network of a PLMN of a second roaming network operator (e.g. China Telecom) among the other roaming network operators, the terminal device sends a registration request to request registration in the first high-standard network. Therefore, the terminal device has more opportunities to preferentially register in the first high-standard network, thereby improving user experiences.

Description

Network registration method and terminal device in roaming scenario

[0001] This application claims priority to the Chinese patent application filed with the State Intellectual Property Office on November 30, 2023, with application number 202311637625.4 and application name “A network registration method and terminal device in a roaming scenario”, the entire contents of which are incorporated by reference into this application. Technical Field

[0002] The present application relates to the field of communications, and more specifically, to a network registration method and terminal device in a roaming scenario in the field of communications. Background Art

[0003] Mobile communications are a widely used communication method worldwide. Terminal devices (e.g., mobile phones) need to search for a public land mobile network (PLMN) and complete network registration on the PLMN before they can perform normal network communications. Currently, international roaming or domestic roaming, referred to as inter-operator roaming, is allowed between operators, and different operators have different PLMNs. For example, if the home operator of a terminal device is operator A, the terminal device can register to the network of another operator that has a roaming agreement with operator A through roaming.

[0004] In a roaming scenario, if the terminal device preferentially searches for a high-standard network (e.g., a 4G network) on the PLMN of an operator (e.g., operator B) in the roaming area but fails to register on the high-standard network of the operator's PLMN, the terminal device receives a registration rejection message including, for example, a reason value #111. In response to the registration rejection message, the terminal device will suspend disabling the high-standard network on the operator's PLMN and suspend network searches on the PLMNs of other operators in the roaming area. Instead, the terminal device will preferentially search for a low-standard network (e.g., a 2G network or a 3G network) on the PLMN of the operator where the network has been searched before. If the operator supports roaming registration of the terminal device to a low-standard network, then when the terminal device searches for the low-standard network of the operator and registers successfully, the terminal device will communicate on the low-standard network, resulting in a poor user experience.

[0005] Summary of the Invention

[0006] An embodiment of the present application provides a network registration method and terminal device in a roaming scenario. When a terminal device fails to register with a high-standard network of a PLMN of a roaming operator in a roaming location, in response to a received registration rejection message, the terminal device searches for a high-standard network on the PLMNs of other roaming operators in the roaming location and attempts to register on the high-standard network. In this way, if a high-standard network exists on the PLMNs of other roaming operators in the roaming location, the terminal device has more opportunities to preferentially register on the high-standard network, thereby improving the user experience of using the network in the roaming scenario.

[0007] In a first aspect, a network registration method in a roaming scenario is provided, comprising: sending a first registration request in a case where a first network is searched for on a PLMN of a first roaming operator in a roaming location, the first registration request being used to request that a terminal device be registered with the first network of the PLMN of the first roaming operator; receiving a registration rejection message in response to the first registration request, the registration rejection message being used to indicate that the terminal device has not successfully registered with the first network of the PLMN of the first roaming operator, and being used to instruct the terminal device to search for a second network having a network standard lower than the first network on the PLMN of the first roaming operator; in response to the registration rejection message, searching for the first network on PLMNs of other roaming operators in the roaming location other than the first roaming operator; and sending a second registration request in a case where the first network is searched for on a PLMN of a second roaming operator among the other roaming operators, to register the terminal device with the first network of the PLMN of the second roaming operator.

[0008] In a network registration method in a roaming scenario provided by an embodiment of the present application, when a terminal device fails to register with a first network (e.g., a 4G network) of a higher standard, such as a PLMN of a first roaming operator (e.g., China Mobile), and receives a registration rejection message instructing the terminal device to search for a second network (e.g., a 3G network or a 2G network) of a lower standard than the first network on the PLMN of the first roaming operator, in response to the registration rejection message, the terminal device searches for the first network of a higher standard on the PLMNs of other roaming operators in the roaming area other than the first roaming operator. In this way, when a first network of a higher standard is found on the PLMN of a second new roaming operator (e.g., China Telecom), the terminal device sends a registration request to register with the first network of a higher standard of the second roaming operator. This increases the terminal device's chance of preferentially registering with the first network of a higher standard, avoids the problem of a poor user experience caused by a terminal device searching for a second network of a lower standard on the PLMN of the first roaming operator and ultimately registering with the second network of a lower standard in the prior art, and effectively improves the user experience of using the network in roaming scenarios.

[0009] In some embodiments, in the above-mentioned step of searching for the first network on the PLMNs of other roaming operators other than the first roaming operator in the roaming area in response to the registration rejection message, the first network is searched on the PLMNs of other roaming operators within a first preset time period in response to the registration rejection message.

[0010] The network registration method in a roaming scenario provided in an embodiment of the present application, by setting a first preset duration, limits the search for the first network on the PLMN of other roaming operators to the first preset duration. This can avoid the problem of the terminal device being unable to access the network due to a long period of continuous searching for the first network, thereby further improving the user experience of using the network in a roaming scenario.

[0011] In some embodiments, after the above-mentioned step of sending a second registration request to register the terminal device with the first network of the PLMN of the second roaming operator when the first network is searched on the PLMN of the second roaming operator among other roaming operators, the method further includes: if the terminal device fails to successfully register with the first network of the PLMN of the second roaming operator and the first preset time has not timed out, continuing to search for the first network on the PLMNs of roaming operators other than the second roaming operator among other roaming operators within the first preset time.

[0012] In this way, the chance of the terminal device searching for the first network can be increased, thereby increasing the chance of registering with the first network and improving the user experience of using the network in a roaming scenario.

[0013] In some embodiments, after the above-mentioned step of sending a second registration request to register the terminal device with the first network of the PLMN of the second roaming operator when the first network is searched on the PLMN of the second roaming operator among other roaming operators, the method further includes: when the terminal device fails to successfully register with the first network of the PLMN of the second roaming operator and the first preset time period times out, searching for a second network with a network standard lower than the first network on the PLMN of at least one roaming operator in the roaming area.

[0014] In the network registration method in a roaming scenario provided in an embodiment of the present application, when a first preset time period expires and a terminal device has not successfully registered with a first network, such as a PLMN of a second roaming operator, in order to enable the terminal device to access the network as quickly as possible, the terminal device no longer searches for the first network, but instead searches for a second network of a lower standard on the PLMN of at least one roaming operator in the roaming area to register with the second network, thereby reducing the risk of the terminal device being unable to access the network for a long time and increasing the probability of the terminal device accessing the network as quickly as possible.

[0015] In some embodiments, the method further includes: before the first preset time period expires and the first network is not found on the PLMN of any roaming operator in other roaming operators, searching for a second network with a lower network standard than the first network on the PLMN of at least one roaming operator in the roaming area before the first preset time period expires.

[0016] In a network registration method in a roaming scenario provided in an embodiment of the present application, if a first network is not found on the PLMN of any roaming operator among other roaming operators before the first preset time expires, this means that the terminal device has traversed all roaming operators among the other roaming operators before the first preset time expires, and the traversal result is that the first network is not found on the PLMN of any roaming operator. In this way, if it is confirmed that the first network has not been found on the PLMNs of other roaming operators, the search duration (i.e., the first preset duration) is terminated early so that a search for a second network of a lower standard can be performed on the PLMN of at least one roaming operator in the roaming area in advance (i.e., before the first preset duration expires). This reduces unnecessary search duration, allows the terminal device to search for other networks earlier and access the network as soon as possible, and improves the user's network experience in the roaming scenario.

[0017] In some embodiments, the method further includes: when the first preset time period expires and the first network has not been searched on the PLMNs of other roaming operators, searching for a second network with a network standard lower than the first network on the PLMNs of at least one roaming operator in the roaming area.

[0018] The network registration method in a roaming scenario provided in an embodiment of the present application no longer searches for the first network after the first preset time period expires, but instead searches for a second network of a lower standard on the PLMN of at least one roaming operator in the roaming area. This allows the terminal device to access the network as much as possible by searching for other networks, reducing the risk of the terminal device being unable to access the network for a long time, thereby increasing the probability of the terminal device accessing the network as soon as possible.

[0019] In some embodiments, the method further includes: searching for a second network with a lower network standard than the first network on the PLMN of at least one roaming operator in the roaming area when the first network is not found on the PLMNs of at least some roaming operators of other roaming operators.

[0020] In this way, the terminal device can try to access the network by searching other networks, reducing the risk of the terminal device being unable to access the network for a long time and increasing the probability of the terminal device accessing the network as soon as possible.

[0021] In some embodiments, the method further includes: searching for a second network having a lower network standard than the first network on the PLMN of at least one roaming operator in the roaming area when the terminal device fails to successfully register with the first network of the PLMN of the second roaming operator.

[0022] In this way, the terminal device can try to access the network by searching other networks, reducing the risk of the terminal device being unable to access the network for a long time and increasing the probability of the terminal device accessing the network as soon as possible.

[0023] In some embodiments, in the above step of searching for a network with a lower network standard than the first network on the PLMN of at least one roaming operator in the roaming area, the second network with a lower network standard than the first network is preferentially searched on the PLMN of the first roaming operator.

[0024] In the network registration method in a roaming scenario provided by an embodiment of the present application, when searching for a second network of a lower standard, a terminal device preferentially searches for the second network on the PLMN of the first roaming operator in which the first network has been previously searched. In this way, the process of searching for the second network of the lower standard can comply with the existing protocol as much as possible, reducing changes to the protocol and achieving the purpose of simplifying the design.

[0025] In some embodiments, in response to the registration rejection message, searching for the first network on the PLMNs of other roaming operators within a first preset duration includes: in response to the registration rejection message, prohibiting the use of the first network of the PLMN of the first roaming operator within a second preset duration, and searching for the first network on the PLMNs of other roaming operators within the first preset duration, the first preset duration being less than the second preset duration.

[0026] In the network registration method in a roaming scenario provided in an embodiment of the present application, due to a registration failure of the first network of the PLMN of the first roaming operator, a second preset duration is set, during which the terminal device is prohibited from using the first network of the PLMN of the first roaming operator. This can avoid the problem that the terminal device may attempt to register with the first network of the PLMN of the first roaming operator multiple times in a short period of time without success, resulting in the terminal device being unable to access the network for a long time.

[0027] In some embodiments, in the above-mentioned step of searching for the first network on the PLMN of other roaming operators within the first preset duration in response to the registration rejection message, a timer is started in response to the registration rejection message, and the duration of the timer is the first preset duration; and the first network is searched on the PLMN of other roaming operators within the duration of the timer.

[0028] In some embodiments, the registration reject message includes any one of the following cause values: cause value #111, cause value #16, cause value #17.

[0029] In some embodiments, the first network is a 5G network or a 4G network.

[0030] In some embodiments, the first network is a 6G network or a higher-standard network.

[0031] In a second aspect, a terminal device is provided, which is configured to execute the method provided in the first aspect. Specifically, the terminal device may include a module configured to execute any possible implementation of the first aspect.

[0032] In a third aspect, a terminal device is provided, comprising a processor. The processor is coupled to a memory and configured to execute instructions in the memory to implement the method of any possible implementation of the first aspect. Optionally, the terminal device further comprises a memory. Optionally, the device further comprises a communication interface, the processor being coupled to the communication interface.

[0033] In a fourth aspect, a computer-readable storage medium is provided, on which a computer program is stored. When the computer program is executed by an apparatus, the apparatus implements the method in any possible implementation manner of the first aspect described above.

[0034] In a fifth aspect, a computer program product comprising instructions is provided, which, when executed by a computer, enables a device to implement the method in any possible implementation of the first aspect.

[0035] In the sixth aspect, a chip is provided, comprising: an input interface, an output interface, a processor and a memory, wherein the input interface, the output interface, the processor and the memory are connected through an internal connection path, and the processor is used to execute the code in the memory. When the code is executed, the processor is used to execute the method in any possible implementation of the first aspect above. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] FIG1 is a schematic scenario diagram of a mobile communication system provided in an embodiment of the present application.

[0037] FIG2 is a schematic diagram of the structure of a terminal device provided in an embodiment of the present application.

[0038] FIG3 is a network registration method in a roaming scenario according to the prior art provided by an embodiment of the present application.

[0039] FIG4 is an exemplary flowchart of a network registration method in a roaming scenario provided by an embodiment of the present application.

[0040] FIG5 is a schematic flowchart of the inter-device interaction of the network registration method in the roaming scenario provided by an embodiment of the present application.

[0041] FIG6 is another schematic flowchart of a network registration method in a roaming scenario provided by an embodiment of the present application.

[0042] FIG7 is another schematic flow chart of a network registration method in a roaming scenario provided by an embodiment of the present application

[0043] FIG8 is an exemplary block diagram of a terminal device provided in an embodiment of the present application.

[0044] FIG9 is a schematic structural diagram of a terminal device provided in an embodiment of the present application. DETAILED DESCRIPTION

[0045] The technical solution in this application will be described below with reference to the accompanying drawings.

[0046] First, a brief introduction is given to the relevant concepts or terms involved in the embodiments of this application.

[0047] Public land mobile network (PLMN)

[0048] A PLMN is a network established and operated by the government or its approved operators to provide land mobile communications services to the public. The PLMN interconnects with the public switched telephone network to form a regional or national communications network. PLMN is synonymous with mobile communications network. In China, each mobile communications operator's network can be considered a PLMN. The networks of China Mobile, China Unicom, and China Telecom are different PLMNs.

[0049] A PLMN consists of a mobile country code (MCC) and a mobile network code (MNC). The MCC uniquely identifies the country of a mobile user. For example, China's MCC is 460. The MNC uniquely identifies a network within that country. For example, the MNC for China Mobile (China Mobile) is 00, the MNC for China Unicom (China Unicom) is 01, the MNC for China Telecom (China Telecom) is 11, and the MNC for China Broadcasting Corporation (China Broadcasting Corporation) is 15. Each operator may have at least one PLMN.

[0050] Table 1 shows the different PLMNs corresponding to different operators.

[0051] Table 1

[0052] As shown in Table 1, China Mobile's PLMNs may include 46000, 46002, 46004, 46007, and 46008; China Unicom's PLMNs may include 46001, 46006, 46009, and 46010. China Telecom's PLMNs may include 46003, 46011, and 46012; and China Broadcasting and Television's PLMNs may include 46015. In the future, each operator's PLMNs may include other PLMNs, which are not limited in this application.

[0053] Home PLMN (HPLMN)

[0054] The HPLMN is the PLMN to which the terminal device belongs, also known as the Home PLMN. The MCC and MNC contained in the International Mobile Subscriber Identification Number (IMSI) on the terminal user's Universal Subscriber Identity Module (USIM) card (also known as the Global Subscriber Identity Card) are consistent with the MCC and MNC on the HPLMN. For a particular terminal device, there is only one Home PLMN. For example, a mobile PLMN includes four PLMNs, and the Home PLMN of a particular terminal device is one of these four PLMNs.

[0055] Home operator and roaming operator

[0056] The home operator is the operator of the terminal device's SIM card, or in other words, the home operator is the operator to which the terminal device's HPLMN belongs. For example, if the terminal device's SIM card is China Mobile's, then China Mobile is the home operator of the terminal device.

[0057] A roaming carrier is an operator in the roaming region, other than the home carrier. For example, in international roaming, if Xiao Wang is a China Mobile user, China Mobile is Xiao Wang's home carrier. If he is on a business trip in Germany, then the local operator in Germany, such as TMO, is the roaming carrier.

[0058] If the home operator has a roaming agreement with a roaming operator, the terminal device can access the PLMN of the roaming operator. For example, if the home operator of the terminal device is China Mobile, and China Mobile has a roaming agreement with Deutsche Telekom's TMO, then when the terminal device roams to Germany, it can access the TMO's PLMN.

[0059] It should be understood that the embodiments of the present application can be applied not only to international roaming scenarios, but also to domestic roaming scenarios. In order to save network construction costs, allowing domestic roaming between operators is an important means to reduce network construction costs. In a domestic roaming scenario, for example, if the home operator of a terminal device is China Unicom, and China Unicom has signed a roaming agreement with China Mobile, then China Mobile is the roaming operator, and China Unicom's terminal device can access China Mobile's network through roaming.

[0060] The technical solutions of the embodiments of the present application are applicable to any communication system that supports roaming services, such as the Global System for Mobile Communications (GSM) system, the General Packet Radio Service (GPRS) system, the Wideband Code Division Multiple Access (WCDMA) system, the Time-Division Code Division Multiple Access (TD-SCDMA) system, the Long Term Evolution (LTE) system, the LTE Frequency Division Duplex (FDD) system, the LTE Time Division Duplex (TDD) system, the Fifth Generation New Radio (5G NR) system, or the future Sixth Generation (6G) system.

[0061] Figure 1 is a schematic scenario diagram of a mobile communication system provided by an embodiment of the present application. Referring to Figure 1, the mobile communication system includes a terminal device, at least one access network device and at least one core network device. The embodiment of the present application does not limit the number of core network devices, access network devices and terminal devices in the mobile communication system. The terminal device is connected to the access network device wirelessly, and the access network device is connected to the core network device wirelessly or wired. The core network device and the access network device can be independent and different physical devices, or the functions of the core network device and the logical functions of the access network device can be integrated into the same physical device, or the functions of some core network devices and some access network devices can be integrated into one physical device. The terminal device can be fixed or movable.

[0062] The access network device is a device that the terminal device uses to access the mobile communication system wirelessly. It can be a base station NodeB, an evolved NodeB (eNodeB), a transmission reception point (TRP), a next-generation base station (next generation NodeB, gNB) in a 5G mobile communication system, a base station in a future mobile communication system, or an access node in a WiFi system. It can also be a wireless controller in a cloud radio access network (CRAN) scenario, a relay station, a vehicle-mounted device, a wearable device, and a network device in a future evolved PLMN network. The embodiments of the present application do not limit the specific technology and specific device form adopted by the access network device.

[0063] A terminal device is any device that can communicate using a SIM card. It may also be referred to as a terminal, user equipment (UE), mobile station (MS), or mobile terminal (MT). A terminal device may be a mobile phone, tablet computer, computer with wireless transceiver capabilities, smartwatch, or the like. The embodiments of this application do not limit the specific technology or device form factor used by the terminal device.

[0064] Different core network devices support different operators. As shown in Figure 1, core network devices 131, 132, 133, and 134 support their respective operators. That is, core network device 131 supports operator B, core network device 132 supports operator C, core network device 133 supports operator D, and core network device 134 supports operator A.

[0065] For an operator, the operator's core network equipment communicates with the terminal equipment through the operator's access network equipment.

[0066] An access network device can support one or more operators. When an access network device supports multiple operators, these operators jointly build and share the access network device to reduce network construction costs. This is especially true for current 5G network access network devices. For the same coverage area, the number of 5G network access network devices required is 3-4 times that of 4G network access network devices. By jointly building and sharing access network devices, network construction costs can be effectively reduced.

[0067] In one example, as shown in FIG1 , access network device 121 , access network device 122 , access network device 124 , and access network device 125 each support one operator, and each operator establishes its own access network device.

[0068] In another example, as shown in Figure 1, the access network device 123 supports two operators: operator B and operator C. That is, operator B and operator C jointly build the access network device 123. In this way, operator B and operator C can share the network of the access network device 123 to reduce the cost of network construction. For example, China Telecom and China Unicom can jointly build a 5G standalone (SA) base station. In this way, China Telecom and China Unicom can share the 5G network of the same base station. For another example, China Radio and Television and China Mobile can jointly build a 5G SA base station. In this way, China Radio and Television and China Mobile can also share the 5G network of the same base station.

[0069] It should be noted that if an access network device supports multiple networks, multiple operators can only share the network jointly built by both parties. For example, if an access network device supports 4G and 5G networks, and the 4G network was independently built by operator B, and operators B and C only jointly built the 5G network, then operators B and C can only share the 5G network, and operator C cannot use the 4G network of the access network device.

[0070] In non-roaming scenarios, a terminal device can access the access network of its home operator. In roaming scenarios, a terminal device can access the access network of a roaming operator that has a roaming agreement with its home operator. As shown in Figure 1, the home operator of terminal device 110 is operator A, access network device 121 is an access network device of operator B, access network device 122 is an access network device of operator C, access network device 123 is an access network device of the 5G network jointly built by operators B and C, access network device 124 is an access network device of operator D, and access network device 125 is an access network device of operator A.

[0071] Assume that operator A has signed a roaming agreement with operator B and operator C for a 5G network, and access network device 121, access network device 122, and access network device 123 all support the 5G network of their respective operators. Then, terminal device 110 can access the 5G networks of the access network devices 121, 122, and 123 of each operator through roaming, and can directly access the network of access network device 125 of the home operator (operator A), but cannot access the network of access network device 124. It should be noted that since access network device 123 is an access network device of the 5G network jointly built and shared by operator B and operator C, and operator A has signed a roaming agreement with operator B and operator C for a 5G network, in a roaming scenario, when terminal device 110 roams between operator B and operator C, it can access access network device 123 through roaming, that is, terminal device 110 accesses the 5G network of the same access network device through roaming.

[0072] Assume again that operator A and operator B have signed a roaming agreement for a 4G network, and operator A and operator C have signed a roaming agreement for a 5G network. Access network device 121 supports operator B's 4G network, access network device 122 supports operator C's 5G network, and access network device 123 supports operator C's 5G network and operator B's 4G network. Then, terminal device 110 can access the 4G network of access network device 121, the 5G network of access network device 122, and the 5G network of operator C of access network device 123 through roaming. It cannot access the 5G network of operator B of access network device 123 or the network of access network device 124, and can directly access the network of access network device 125 of the home operator (operator A). It should be noted that although the access network device 123 is an access network device of the 5G network jointly built and shared by operators B and C, operator A has only signed a roaming agreement for the 5G network with operator C. Therefore, in the roaming scenario, the terminal device 110 can only access the 5G network of operator C of the access network device 123 through roaming and cannot access the 5G network of operator B of the access network device 123.

[0073] It should be understood that the mobile communication system shown in FIG1 is merely an illustrative example and should not limit the embodiments of the present application. For example, the mobile communication system may include more or fewer core network devices, access network devices, and terminal devices.

[0074] Figure 2 shows a schematic diagram of the structure of a terminal device 110. Terminal device 110 may include, but is not limited to, components such as a processor 111, antenna 1, antenna 2, a mobile communication module 112, a wireless communication module 113, and a subscriber identification module (SIM) card interface 114. For example, terminal device 110 may also include an audio module 115, a display screen 116, a camera 117, a sensor module 118, an external memory interface, internal memory, a universal serial bus (USB) interface, a charging management module, a power management module, a battery, buttons, a motor, and an indicator.

[0075] It should be understood that the structure illustrated in the embodiments of the present application does not constitute a specific limitation on the terminal device 110. In other embodiments of the present application, the terminal device 100 may include more or fewer components than shown, or may combine or separate certain components, or arrange the components differently. The illustrated components may be implemented in hardware, software, or a combination of software and hardware.

[0076] The processor 111 may include one or more processing units, for example: the processor 111 may include an application processor (AP), a modem processor, a graphics processing unit (GPU), an image signal processor (ISP), a controller, a memory, a video codec, a digital signal processor (DSP), a baseband processor, and / or a neural-network processing unit (NPU), etc. Among them, different processing units can be independent devices or integrated into one or more processors. Among them, the controller can be the nerve center and command center of the terminal device 110. The controller can generate an operation control signal based on the instruction opcode and timing signal to complete the control of instruction fetching and execution.

[0077] Processor 110 may also include a memory for storing instructions and data. In some embodiments, the memory in processor 110 is a cache memory. This memory can store instructions or data that have just been used or are being recycled by processor 110. If processor 110 needs to use the same instruction or data again, it can directly retrieve it from the memory. This avoids duplicate accesses, reduces processor 110 latency, and thus improves system efficiency.

[0078] In an embodiment of the present application, the processor 110 searches for a network in a roaming scenario. After searching for a high-standard network (e.g., a 4G network or a 5G network) of a PLMN of a roaming operator in the roaming area, the processor 110 sends a registration request to request network registration. If the registration is successful, the processor 110 resides in the network for communication. If the registration fails, the processor 110 searches for a network of the same standard on the PLMNs of other roaming operators in the roaming area to attempt to register on the high-standard network. Furthermore, if a high-standard network is not found on the PLMNs of other roaming operators, the processor 110 searches for a low-standard network (e.g., a 3G network or a 2G network) of a lower standard on the PLMNs of at least one roaming operator in the roaming area to allow the terminal device to access the network as much as possible.

[0079] The wireless communication function of the terminal device 110 can be implemented through antenna 1, antenna 2, mobile communication module 112, wireless communication module 113, modem processor and baseband processor.

[0080] Antenna 1 and Antenna 2 are used to transmit and receive electromagnetic wave signals. Each antenna in terminal device 110 can be used to cover a single or multiple communication frequency bands. Different antennas can also be reused to improve antenna utilization. For example, antenna 1 can be reused as a diversity antenna for a wireless local area network. In other embodiments, the antennas can be used in conjunction with a tuning switch.

[0081] The mobile communication module 112 can provide solutions for wireless communications including 2G / 3G / 4G / 5G applied to the terminal device 110. The mobile communication module 112 may include at least one filter, a switch, a power amplifier, a low noise amplifier (LNA), etc. The mobile communication module 112 can receive electromagnetic waves from the antenna 1, and filter, amplify, and process the received electromagnetic waves, and transmit them to the modulation and demodulation processor for demodulation. The mobile communication module 112 can also amplify the signal modulated by the modulation and demodulation processor, and convert it into electromagnetic waves for radiation through the antenna 1. In some embodiments, at least some of the functional modules of the mobile communication module 112 can be set in the processor 111. In some embodiments, at least some of the functional modules of the mobile communication module 112 can be set in the same device as at least some of the modules of the processor 111.

[0082] The wireless communication module 113 can provide wireless communication solutions including wireless local area networks (WLAN) (such as wireless fidelity (Wi-Fi) networks), Bluetooth (BT), global navigation satellite system (GNSS), frequency modulation (FM), near field communication (NFC), infrared (IR), etc., which are applied to the terminal device 110. The wireless communication module 113 can be one or more devices that integrate at least one communication processing module. The wireless communication module 113 receives electromagnetic waves via the antenna 2, frequency modulates and filters the electromagnetic wave signals, and sends the processed signals to the processor 111. The wireless communication module 113 can also receive the signal to be sent from the processor 111, frequency modulate it, amplify it, and convert it into electromagnetic waves for radiation through the antenna 2.

[0083] In some embodiments, the antenna 1 of the terminal device 110 is coupled to the mobile communication module 112, and the antenna 2 is coupled to the wireless communication module 113, so that the terminal device 110 can communicate with the network and other devices through wireless communication technology. The wireless communication technology may include GSM, GPRS, WCDMA, TD-SCDMA, LTE, FDD, TDD, 5G NR or 6G system, BT, GNSS, WLAN, NFC, FM, and / or IR technology. The GNSS may include a global positioning system (GPS), a global navigation satellite system (GLONASS), a Beidou navigation satellite system (BDS), a quasi-zenith satellite system (QZSS) and / or a satellite-based augmentation system (SBAS).

[0084] The SIM card of the terminal device supports different mobile networks of various operators. The terminal device can interact with various mobile networks through the SIM card and the mobile communication module 112 to achieve mobile calls and data communications. For example, if the SIM card of the terminal device is a telecom card, the terminal device can interact with the telecom network through the SIM card and the mobile communication module 112 to achieve mobile calls and data communications on the telecom network.

[0085] The SIM card interface 114 is used to connect a SIM card. A SIM card can be connected to and disconnected from the terminal device 110 by inserting or removing it from the SIM card interface 114. The terminal device 110 may support one or N SIM card interfaces, where N is a positive integer greater than 1. The SIM card interface 114 may support Nano SIM cards, Micro SIM cards, SIM cards, and other types of cards. Multiple cards can be inserted into the same SIM card interface 114 simultaneously. These cards can be of the same or different types. The SIM card interface 114 is also compatible with different types of SIM cards. The SIM card interface 114 is also compatible with external memory cards. The terminal device 110 interacts with the networks of various carriers through the SIM card to implement functions such as call and data communications.

[0086] Figure 3 illustrates a network registration method for a roaming scenario in the prior art, provided by an embodiment of the present application. In this case, a terminal device roams to a roaming location and needs to access the network of the roaming location through roaming. Operator B is the operator of the roaming location, access network device A supports operator B's 4G network, and access network device B supports operator B's 3G and 2G networks.

[0087] In step S310, the terminal device roams to a roaming location and searches for a 4G network of the PLMN of operator B in the roaming location.

[0088] In the roaming scenario, the terminal device searches for networks in descending order of network standards, and preferentially searches for the 4G network of the PLMN of operator B. It should be understood that compared with 3G and 2G networks, the 4G network is a high-standard network.

[0089] In step S320, the terminal device sends a 4G network registration request to the access network device A to request registration to the 4G network of the PLMN of operator B.

[0090] In step S330, in response to the registration request, access network device A sends a registration rejection message to the terminal device, indicating that the terminal device has not successfully registered with the 4G network of the PLMN of operator B. The registration rejection message includes a reason value for network registration failure.

[0091] It should be noted that if a terminal device fails to register with the network, there are generally two reasons: one is network reasons, such as network interruption, system failure, etc.; the other is user reasons, such as network rejection due to the user not having a GPRS subscription or a roaming agreement. The terminal device will determine the reason for the registration failure based on the cause value in the registration rejection message fed back by the access network device.

[0092] For example, common user cause values ​​include Cause #7, indicating GPRS service is not allowed; Cause #11, indicating PLMN is not allowed; and common network cause values ​​include Cause #16, indicating that the mobile switching center (MSC) is temporarily unreachable; Cause #17, indicating network failure; and Cause #111, indicating a protocol error.

[0093] In the above step S330, the cause value included in the registration rejection message may be a network registration failure caused by a network reason such as Cause#16, Cause#17, and Cause#111. Based on the cause value, the terminal device executes step S340.

[0094] In step S340 , the terminal device disables the 4G network of the PLMN of operator B within a preset time (eg, 12 minutes), and preferentially searches for a low-standard 3G network or 2G network on the PLMN of operator B.

[0095] The terminal device receives the registration rejection message sent by access network device A. The reason for the network registration failure can be determined based on the reason value in the registration rejection message. Based on the protocol, the terminal device disables the 4G network of operator B within a preset time (for example, 12 minutes) and preferentially searches for 3G or 2G networks with network standards lower than 4G on operator B's PLMN.

[0096] It should be understood that the priority here to search for low-standard 3G networks or 2G networks on operator B's PLMN means that after failing to successfully register on the 4G network of operator B's PLMN, the terminal device will first search for the 3G network or 2G network on operator B's PLMN to try to register the 3G network or 2G network on operator B's PLMN. During this period, the terminal device will temporarily not search for networks of any standards on other operators' PLMNs. Only when the registration on the 3G network or 2G network of operator B's PLMN fails or the 3G network or 2G network is not searched, the terminal device will try to search for networks on other operators' PLMNs.

[0097] In step S350, the terminal device searches for the 3G network of the PLMN of operator B.

[0098] In step S360, the terminal device sends a 3G network registration request to the access network device B to request registration to the 3G network of the PLMN of operator B.

[0099] In step S370, access network device B sends a registration success message to the terminal device.

[0100] At this point, it means that the terminal device has successfully registered with operator B's 3G network.

[0101] In step S380, after the preset time expires, the terminal device releases the disabled state of the 4G network of operator B's PLMN, performs reselection or redirection processes to return to the 4G network and retry to register on the 4G network. If the registration fails, step S340 and subsequent steps are continued to finally register to the 3G network. If the registration is successful, it resides in the 4G network.

[0102] It can be seen that in the above roaming scenario, if the terminal device preferentially searches for a high-standard network (for example, a 4G network) on the PLMN of a roaming operator (for example, operator B) but fails to register with the high-standard network of the PLMN of the roaming operator, the terminal device will respond to the received registration rejection message including, for example, the reason value #111, and will suspend the use of the high-standard network of the roaming operator and suspend the search for networks on the PLMNs of other roaming operators. Instead, it will preferentially search for low-standard networks (for example, 2G networks or 3G networks) on the PLMN of the roaming operator. If a low-standard network is found on the PLMN of the roaming operator, the terminal device will register to the low-standard network of the roaming operator through roaming.

[0103] However, in the network registration process of the above-mentioned roaming scenario, if the terminal device itself supports roaming registration to the high-standard network of the PLMN of other roaming operators (for example, operator C), but the terminal device fails to register in the high-standard network of the PLMN of a certain roaming operator (for example, operator B) and receives a registration rejection message including, for example, reason value #111, the search for the PLMN of other roaming operators will be suspended, resulting in the terminal device being able to register only to the low-standard network and unable to register to the high-standard network of other roaming operators, resulting in a poor user experience.

[0104] Based on this, an embodiment of the present application provides a network registration method in a roaming scenario. When a terminal device fails to register for a high-standard network of a PLMN of a roaming operator in the roaming area, in response to the received registration rejection message, the terminal device will search for a high-standard network on the PLMN of other roaming operators in the roaming area to attempt to register to the high-standard network. In this way, when a high-standard network exists on the PLMN of other roaming operators in the roaming area, the terminal device has more opportunities to register to the high-standard network first, thereby improving the user experience.

[0105] The network registration method in a roaming scenario of the embodiment of the present application can be applied to any roaming scenario. For example, the method can be applied to scenarios such as a terminal device first accessing a network in a roaming location, reselecting a network in a roaming location, and restarting a terminal device in a roaming location to access a network again.

[0106] Hereinafter, the network registration method in a roaming scenario according to an embodiment of the present application will be described in detail with reference to FIG. 4 to FIG. 7 .

[0107] In the embodiment of the present application, the method 400 is described in detail by taking the terminal device as the execution subject of the method 400. As an example but not a limitation, the execution subject of the method 400 may also be a chip or processor of the corresponding terminal device.

[0108] Figure 4 is an exemplary flow chart of a network registration method 400 in a roaming scenario provided by an embodiment of the present application. Figure 5 is a schematic flow chart of device-to-device interaction of a network registration method 400 in a roaming scenario provided by an embodiment of the present application.

[0109] In step S410, when a first network is found on the PLMN of the first roaming operator in the roaming area, a first registration request is sent, where the first registration request is used to request registration with the first network of the PLMN of the first roaming operator.

[0110] In the above steps, the terminal device may automatically search for a network or perform a network search based on a network search instruction input by the user. If the user is currently in a roaming location, the user's terminal device searches for a first network of a PLMN of a first roaming operator in the roaming location. The terminal device then sends a first registration request to the access network device, requesting registration with the first network of the PLMN of the first roaming operator currently searched. It should be understood that the first roaming operator is any operator in the roaming location.

[0111] In the process of searching for a network, the terminal device can search for networks in order of network standards from high to low. Therefore, the first network searched by the terminal device can be considered to be the network with the highest network standard that the terminal device can (or is allowed to) search at present. For example, if the first network is a 4G network, it can be considered that the 4G network is the network with the highest network standard that the terminal device can currently search. For the 5G network, the terminal device may not have successfully searched for the 5G network due to reasons such as previous registration failure or failure to search for a signal. For another example, if the first network is a 5G network, it can be considered that the 5G network is the network with the highest network standard that the terminal device can search for. For another example, if the first network is a 3G network, it can be considered that the 3G network is the network with the highest network standard that the terminal device can search for. For the 4G network or 5G network, the terminal device may not have successfully searched for the relevant network due to reasons such as previous registration failure or failure to search for a signal.

[0112] It should be understood that in the case where the first roaming operator includes multiple PLMNs, the first network of the PLMN of the first roaming operator searched by the terminal device is the first network of any PLMN of the first roaming operator. No limitation is made here, and the specific PLMN searched by the terminal device in the actual scenario shall prevail.

[0113] 5 , taking the example of access network device #1 supporting the first network of the first roaming operator, illustratively, in step S411, when the first network is searched on the PLMN of the first roaming operator in the roaming location, the terminal device sends a first registration request to access network device #1.

[0114] In step S420, the terminal device receives a registration rejection message in response to the first registration request. The registration rejection message is used to indicate that the terminal device has not successfully registered with the first network of the PLMN of the first roaming operator and is used to instruct the terminal device to search for a second network with a lower network standard than the first network on the PLMN of the first roaming operator.

[0115] It can be understood that compared with the first network, the second network is a low-standard network and the first network is a high-standard network.

[0116] In this step, the access network device receives the first registration request and, in response to the first registration request, sends a registration rejection message to the terminal device, which then receives the registration rejection message. Based on the registration reason message, the terminal device knows the following two things: first, the terminal device failed to successfully register with the first network (e.g., 4G network) of the PLMN of the first roaming operator (e.g., China Mobile) for which registration was requested; and second, the terminal device needs to search for a second network (e.g., 3G network or 2G network) on the PLMN of the first roaming operator (e.g., China Mobile) with a network standard lower than the first network (e.g., 4G network).

[0117] It should be understood that the registration rejection message indicates that while the terminal device searches for a second network with a network standard lower than the first network on the PLMN of the first roaming operator, the terminal device will not search for a network with any network standard on the PLMN of other roaming operators.

[0118] The Registration Reject message includes a reason value indicating a registration failure. This application does not impose any restrictions on the specific content of the reason value, as long as the reason value can express the meaning of "the terminal device failed to successfully register with the first network of the PLMN of the first roaming operator" and can express the meaning of "the terminal device searched for a second network with a lower network standard than the first network on the PLMN of the first roaming operator." Generally, the reason value in the Registration Reject message of this application indicates the reason for the registration failure due to network reasons.

[0119] Exemplarily, the cause value can be any of the following: cause value #111, cause value #16, or cause value #17. Cause value #111 indicates a protocol error, cause value #16 indicates that the MSC is temporarily unreachable, and cause value #17 indicates a network failure. All three cause values ​​indicate registration failures due to network issues.

[0120] For the reason value #111, the terminal device can execute step S430 after a registration failure, that is, the terminal device can execute step S430 after receiving the first registration rejection message including the reason value #111.

[0121] For reason values ​​#16 and #17, the protocol stipulates that the terminal device can have five consecutive opportunities to register with the network. In other words, as long as network registration is unsuccessful, the terminal device can initiate five registration requests to request registration with the network. Therefore, in order to comply with the protocol to the greatest extent possible, in the embodiment of the present application, the terminal device can execute step S430 after sending a registration request for the fifth time and failing to successfully register with the network. In other words, the terminal device can execute step S430 after receiving the fifth registration rejection message including reason value #16 or reason value #17.

[0122] Referring to Figure 5, continuing to take the access network device #1 supporting the first network of the first roaming operator as an example, illustratively, in step S421, after the access network device #1 receives the first registration request sent by the terminal device, it responds to the first registration request and sends a registration rejection message to the terminal device.

[0123] In step S430 , in response to the registration rejection message, the terminal device searches for the first network on PLMNs of other roaming operators except the first roaming operator in the roaming area.

[0124] In this step, when the terminal device receives the registration rejection message sent by the access network device, it does not search for a second network (e.g., a 3G network or a 2G network) with a network standard lower than the first network (e.g., a 4G network) on the PLMN of the first roaming operator (e.g., China Mobile) as in the prior art. Instead, it searches for the first network (e.g., a 4G network) on the PLMNs of other roaming operators (e.g., China Unicom, China Telecom, or China Broadcasting Corporation) in the roaming area other than the first roaming operator (e.g., China Mobile). In this way, the terminal device searches for a higher-standard first network on other roaming operators, which can give the terminal device more opportunities to access the higher-standard first network as early as possible, thereby improving user experience.

[0125] It should be noted that the "other roaming operators" here can be at least one roaming operator other than the first roaming operator, and does not necessarily mean all operators other than the first roaming operator. This is not a limitation. For example, if a terminal device roams from abroad to China, and there are four roaming operators in China, and the first roaming operator is China Mobile, then the "other roaming operators" can be at least one of China Unicom, China Telecom, and China Radio and Television.

[0126] It should also be noted that when a terminal device searches for the first network on the PLMNs of other roaming operators, it means that the terminal device can search for the first network on the PLMNs of other roaming operators, and the terminal device does not necessarily search every roaming operator among the other roaming operators. For example, if the other roaming operators include three roaming operators, and during the network search process, the terminal device first searches for the first network on one of the roaming operators and successfully registers with the first network, then the terminal device does not need to continue searching for the first network on the remaining two roaming operators.

[0127] It should be understood that while the terminal device is searching for the first network on the PLMNs of other roaming operators, the terminal device will not search for any network of any standard on the PLMN of the first roaming operator. Only when the first network is not found on the PLMNs of other roaming operators or the registration for the first network fails, will it be possible to search for a network of a lower standard on the PLMN of the first roaming operator.

[0128] In step S440, when the terminal device searches for the first network on the PLMN of the second roaming operator among other roaming operators, the terminal device sends a second registration request to register the terminal device with the first network of the PLMN of the second roaming operator.

[0129] That is, if the terminal device searches for a high-standard first network on the PLMN of the second roaming operator, the terminal device then sends a second registration request to the access network device to register the terminal device with the first network of the second roaming operator's PLMN. If the terminal device successfully registers, the access network device sends a registration success message to the terminal device, indicating that the terminal device has successfully registered with the first network of the second roaming operator's PLMN. Thereafter, the terminal device can communicate on the first network of the second roaming operator's PLMN. The second roaming operator is any operator in the roaming area other than the first roaming operator.

[0130] In one example, the second roaming operator and the first roaming operator can jointly build and share the same access network device, such as access network device 123 shown in Figure 1. The second roaming operator and the first roaming operator can share the first network of the same access network device. In this example, the terminal device sends the first registration request and the second registration request to the same access network device.

[0131] In another example, the second roaming operator and the first roaming operator each use different access network devices. Referring to Figure 5 , taking the example of access network device #1 supporting the first network of the first roaming operator and access network device #2 supporting the first network of the second roaming operator, in step S441, the terminal device sends a second registration request to access network device #2, requesting registration with the first network of the second roaming operator's PLMN. If the terminal device successfully registers, in step S450, access network device #2 sends a registration success message to the terminal device, indicating that the terminal device has successfully registered with the first network of the second roaming operator's PLMN. Thereafter, the terminal device can communicate on the first network of the second roaming operator's PLMN.

[0132] It should be understood that in the case where the second roaming operator includes multiple PLMNs, the first network of the PLMN of the second roaming operator searched by the terminal device is the first network of any PLMN of the second roaming operator. No limitation is made here, and the specific PLMN searched by the terminal device in the actual scenario shall prevail.

[0133] As a specific example, the home operator of the terminal device is the TMO of Deutsche Telekom. The user of the terminal device moves from Germany to China. The four operators in China (China Mobile, China Unicom, China Telecom and China Broadcasting Corporation) are the roaming operators of the terminal device. After the terminal device is turned on, it searches for a 4G network (an example of the first network) of a PLMN of China Mobile (an example of the first roaming operator) and sends a registration request to request registration to the 4G network of China Mobile's PLMN. After the terminal device receives a registration rejection message including, for example, a reason value #111 for the failure to register with China Mobile's 4G network, the terminal device stops searching for the 4G network on China Mobile's PLMN, and does not search for a 3G network or a 2G network on China Mobile's PLMN as in the prior art. Instead, it searches for a 4G network on the PLMN of at least one operator among China Unicom, China Telecom and China Broadcasting Corporation. After searching for a 4G network on China Telecom's PLMN, it sends a registration request to register the terminal device to China Telecom's 4G network.

[0134] In the network registration method provided above in the roaming scenario, if a terminal device fails to register with a first network (e.g., a 4G network) of a higher standard in a PLMN of a first roaming operator (e.g., China Mobile) and receives a registration rejection message instructing the terminal device to search for a second network (e.g., a 3G network or a 2G network) of a lower standard than the first network on the PLMN of the first roaming operator, in response to the registration rejection message, the terminal device searches for the first network on PLMNs of other roaming operators in the roaming area other than the first roaming operator. In this way, if a first network of a higher standard is found on a PLMN of a second roaming operator (e.g., China Telecom) of the other roaming operators, the terminal device sends a registration request to request registration with the first network of a higher standard. This increases the terminal device's chance of preferentially registering with the first network of a higher standard, avoids the problem in the prior art where a terminal device searches for a second network of a lower standard in the PLMN of the first roaming operator and ultimately registers with the second network of a lower standard, resulting in a poor user experience, and effectively improves the user experience.

[0135] In some embodiments, if the terminal device fails to successfully register with the first network of the PLMN of the second roaming operator, the terminal device searches for a second network with a lower network standard than the first network on the PLMN of at least one roaming operator in the roaming region. In other words, if the terminal device fails to successfully register, the terminal device searches for a second network with a lower network standard than the first network on the PLMN of at least one roaming operator in the roaming region.

[0136] It should be noted that the at least one roaming operator in the roaming location herein may be some or all of the operators in the roaming location, without any limitation. The at least one roaming operator in the roaming location may include or exclude the first roaming operator, without any limitation. The explanation of "at least one roaming operator in the roaming location" in the following similar description of "searching for a second network with a lower network standard than the first network (or searching for a second network with a lower network standard) on the PLMN of at least one roaming operator in the roaming location" is the same here and will not be repeated.

[0137] It should also be noted that when a terminal device searches for a second network on the PLMN of at least one roaming operator in a roaming location, it means that the terminal device is able to search for the second network on the PLMN of the at least one roaming operator, and the terminal device does not necessarily search through every roaming operator in the at least one roaming operator. For example, if the at least one roaming operator includes three roaming operators, and during the network search process, the terminal device first searches for and successfully registers with a second network on one of the roaming operators, then the terminal device does not need to continue searching for the second network on the remaining two roaming operators. The explanations for similar descriptions below are the same and will not be repeated here.

[0138] Regarding the process in which a terminal device searches for a second network having a lower network standard than the first network on the PLMN of at least one roaming operator, two possible implementations are exemplified below.

[0139] Method 1

[0140] In some embodiments, the operator is prioritized. For a roaming operator, the terminal device attempts to search for second networks of all network standards on the PLMN of the roaming operator in descending order of network standards. If a second network of any network standard is found, a registration request is initiated to request network registration. If the registration is successful, networks of other network standards are no longer searched. If the registration is not successful, the search for networks of other network standards continues. If the second network of all network standards is not found on the PLMN of the roaming operator, the terminal device attempts to search for second networks of all network standards on the PLMN of another roaming operator until a second network of any network standard is found on the PLMN of any roaming operator.

[0141] Assuming that the first network is a 4G network, and the terminal device fails to register on the mobile PLMN and the first preset time expires, the terminal device can search for a 3G network or a 2G network with a network standard lower than the 4G network on the PLMN of China Mobile, China Unicom, China Telecom and China Radio and Television. Here, 3G and 2G can be regarded as two network standards of the second network. In the process of searching for 3G network or 2G network, the terminal device first searches for 3G network on the mobile PLMN. If a 3G network is found, a registration request for the 3G network is initiated to request registration to the 3G network. If the registration is successful, the mobile 2G network is no longer searched. If the registration is not successful or the mobile 3G network is not found, the terminal device continues to search for 2G network on the mobile PLMN. Similarly, if a 2G network is found, a registration request for the 2G network is initiated to request registration to the 2G network. If the registration is successful, the network of other roaming operators is no longer searched. If the registration is not successful or the mobile 2G network is not found, the 3G network or 2G network is searched on the PLMN of another roaming operator (for example, China Unicom) in descending order of network standards until a 3G network or 2G network is found on the PLMN of any roaming operator.

[0142] Method 2

[0143] In other embodiments, the network standard is prioritized. For one network standard, the terminal device attempts to search for a second network under the network standard on the PLMNs of various roaming operators. If the second network of the network standard is found on the PLMNs of any roaming operator, a registration request is initiated to request network registration. If the registration is successful, the second network of the network standard of other roaming operators is no longer searched. If the registration is unsuccessful, the second network of the network standard of other roaming operators is continued to be searched. If the second network of the network standard is not found on the PLMNs of any roaming operator, for another network standard, the terminal device attempts to search for the second network of the other network standard on the PLMNs of various roaming operators until a second network of any network standard is found on the PLMNs of any roaming operator.

[0144] Assuming that the first network is a 4G network, if the terminal device fails to register on the China Mobile PLMN and the first preset duration times out, the terminal device may search for a 3G network or a 2G network with a network standard lower than the 4G network on the PLMNs of China Mobile, China Unicom, China Telecom, and China Broadcasting Corporation. Here, 3G and 2G can be regarded as two network standards of the second network. When searching for a 3G network or a 2G network, the 3G network is prioritized. The terminal device searches for the 3G network on the PLMN of China Mobile. If a 3G network is found, a registration request for the 3G network is initiated to request registration to the 3G network. If the registration is successful, the 3G networks of China Unicom, China Telecom and China Broadcasting Corporation will no longer be searched. If the registration is not successful or the 3G network of China Mobile is not found, the terminal device searches for the 3G network on the PLMNs of China Unicom, China Telecom and China Broadcasting Corporation until a 3G network is found and registration is successful on the PLMN of any roaming operator. If a 3G network is not found on the PLMN of any roaming operator, the terminal device starts searching for the 2G network on the PLMNs of China Mobile, China Unicom, China Telecom and China Broadcasting Corporation until a 2G network is found on the PLMN of any roaming operator.

[0145] Illustratively, in the step of the terminal device searching for a second network with a lower network standard than the first network on the PLMN of at least one roaming operator in the roaming region, the terminal device preferentially searches for the second network with a lower network standard than the first network on the PLMN of the first roaming operator. It is understood that the at least one roaming operator includes the first roaming operator.

[0146] In this embodiment, when searching for a second network of a lower standard, the terminal device prioritizes searching for the second network on the PLMN of the first roaming operator, which has previously searched for the first network. If the second network is found on the PLMN of the first roaming operator, the terminal device initiates a registration request to attempt to register with the second network. If the second network is not found on the PLMN of the first roaming operator, the terminal device may continue searching for the second network on the PLMNs of other roaming operators. In this way, the process of searching for a second network of a lower standard can adhere to existing protocols as much as possible, reducing protocol modifications and simplifying the design.

[0147] The terminal device preferentially searches for the second network on the PLMN of the first roaming operator. In one example, for the above-mentioned method 1, it can be understood that the terminal device preferentially attempts to search for the second network of all network standards on the PLMN of the first roaming operator; in another example, for the above-mentioned method 2, it can be understood that when searching for the second network of the same network standard on the PLMN of at least one roaming operator, the terminal device preferentially attempts to search for the second network of the network standard on the PLMN of the first roaming operator.

[0148] In some embodiments, when the first network is not found on the PLMNs of at least some of the other roaming operators, a second network with a lower network standard than the first network is searched on the PLMNs of at least one roaming operator in the roaming area.

[0149] That is, when the terminal device fails to search for the first network, the terminal device will search for a second network of a lower standard on the PLMN of at least one roaming operator in the roaming area.

[0150] It should be understood that the phrase "at least some of the roaming operators" herein refers to some or all of the other roaming operators. Due to certain restrictions (e.g., the time limit of method 600 below) or network issues, the terminal device may not be able to search for all of the other roaming operators. Therefore, the terminal device may search for a second network of a lower standard after searching for some of the roaming operators.

[0151] For a detailed description of the terminal device searching for a second network with a network standard lower than the first network on the PLMN of at least one roaming operator in the roaming area, please refer to the above related description and will not be repeated here.

[0152] In some embodiments, the registration rejection message is also used to instruct the terminal device to prohibit the use of the first network of the PLMN of the first roaming operator within a second preset time period, and, in the above-mentioned step S430, that is, the step of searching for the first network on the PLMNs of other roaming operators in response to the registration rejection message, the terminal device prohibits the use of the first network of the PLMN of the first roaming operator within the second preset time period in response to the registration rejection message, and searches for the first network on the PLMNs of other roaming operators.

[0153] The second preset duration can be any duration and is not limited herein. For example, the second preset duration is less than or equal to 15 minutes. For example, the second preset duration can be 14 minutes, 13 minutes, 12 minutes, 10 minutes, 9 minutes, 8 minutes, 7 minutes, etc.

[0154] Since the registration of the first network of the PLMN of the first roaming operator failed, in order to avoid the problem that the terminal device may try to register the first network of the PLMN of the first roaming operator multiple times in a short period of time and all fail, resulting in the terminal device being unable to access the network, a second preset time period is limited. During the second preset time period, the terminal device is prohibited from using the first network of the PLMN of the first roaming operator, and during the period of disabling the first network of the PLMN of the first roaming operator, the first network is searched for on the PLMNs of other roaming operators first.

[0155] In the above embodiment, after the second preset duration expires, the terminal device removes the disabled state from the first network of the PLMN of the first roaming operator. Thus, the terminal device can return to the first network by performing a reselection or redirection process to retry registration with the first network. If registration fails, step S430 and subsequent steps are continued. If registration succeeds, the terminal device remains on the first network. Thus, if the terminal device ultimately fails to successfully register with the first network, removing the disabled state from the first network of the PLMN of the first roaming operator gives the terminal device another opportunity to return to the higher-standard first network and attempt registration with the first network, thereby maximizing the user experience.

[0156] In the above embodiment, a timer (defined as a second timer) may be set to control the second preset duration.

[0157] Exemplarily, in response to the registration rejection message, the terminal device starts a second timer to prohibit use of the first network of the PLMN of the first roaming location for a duration of the second timer, where the duration of the second timer is a second preset duration; the terminal device searches for the first network on PLMNs of other roaming location operators. Furthermore, after the second timer expires, the terminal device releases the prohibition status of the first network of the PLMN of the first roaming location operator.

[0158] It should be noted that, when the first roaming operator includes multiple PLMNs, in step S410, no matter which PLMN of the first roaming operator the terminal device searches for the first network, after receiving the registration rejection message, the terminal device will prohibit the use of the first network on all PLMNs of the first roaming operator.

[0159] In some embodiments, in the above-mentioned step S430, i.e., the step of searching for the first network on the PLMN of other roaming operators in response to the registration rejection message, the terminal device searches for the first network on the PLMN of other roaming operators within a first preset time period in response to the registration rejection message.

[0160] Exemplarily, the first preset time length is less than or equal to 2 minutes. For example, the first preset time length may be 2 minutes, 1.5 minutes, 1 minute, 0.5 minutes, etc.

[0161] In the embodiment of the present application, different first preset durations can be set for first networks of different network standards. There is no specific limitation on the first preset durations for first networks of different network standards and they can be flexibly set based on actual conditions. For example, for a 5G network, the first preset duration is duration 1, for a 4G network, the first preset duration is duration 2, and for a 3G network, the first preset duration is duration 3, where duration 1, duration 2, and duration 3 are all different.

[0162] In some embodiments, generally speaking, networks with higher network standards have more frequencies, and searching for these networks takes longer. Therefore, in order to enable the terminal device to search for higher-standard networks as much as possible, the higher the network standard of the first network, the longer the first preset duration is set. For example, the first preset duration for a 5G network is longer than the first preset duration for a 4G network.

[0163] In the above embodiment, by setting a first preset time duration and limiting the search for the first network on the PLMN of other roaming operators to the first preset time duration, the problem of the terminal device being unable to access the network due to long-term continuous search for the first network can be avoided, thereby further improving the user experience.

[0164] In the above embodiment, a timer (defined as a first timer) may be set, and the first preset duration may be controlled by the timer.

[0165] Exemplarily, in response to the registration rejection message, the terminal device starts a first timer, where the duration of the first timer is a first preset duration; the terminal device searches for the first network on the PLMN of other roaming operators within the duration of the first timer.

[0166] In combination with the above-mentioned second preset duration for limiting the first network of the PLMN of the first roaming operator, in some embodiments, the terminal device prohibits the use of the first network of the PLMN of the first roaming operator within the second preset duration in response to the registration rejection message, and searches for the first network on the PLMNs of the other roaming operators within the first preset duration, wherein the first preset duration is less than the second preset duration.

[0167] That is, during the second preset duration during which the use of the first network of the PLMN of the first roaming operator is prohibited, the terminal device searches for the first network on the PLMNs of other roaming operators for the first network during the first preset duration. After the first preset duration expires, regardless of the terminal device's status (successfully registered with the first network, unsuccessfully registered with the first network, or failed to search for the first network), the terminal device stops searching for the first network on any PLMN of the other roaming operators, and because the second preset duration has not expired, the terminal device is still prohibited from using the first network of the PLMN of the first roaming operator.

[0168] Exemplarily, the second preset time length is 12 minutes, and the first preset time length is less than or equal to 2 minutes. For example, the first preset time length can be 2 minutes, 1.5 minutes, 1 minute, 0.5 minutes, etc.

[0169] In conjunction with the first timer and the second timer defined above, illustratively, in response to the registration rejection message, the terminal device starts the second timer to prohibit the use of the first network of the PLMN of the first roaming location during the duration of the second timer; and starts the first timer to search for the first network on the PLMNs of other roaming operators during the duration of the first timer. The duration of the first timer is a first preset duration, and the duration of the second timer is a second preset duration, where the first preset duration is less than the second preset duration.

[0170] It should be understood that the steps of starting the second timer and the first timer of the terminal device can be performed simultaneously, or the second timer can be started first and then the first timer. There is no limitation here.

[0171] Figure 6 is a schematic flow chart of a network registration method 600 in a roaming scenario provided by an embodiment of the present application. In method 600, various situations in which a terminal device searches for a network are described in detail in combination with the first preset duration and the second preset duration.

[0172] In step S611, the terminal device searches for the first network on the PLMN of the first roaming location.

[0173] In step S612, when the first network is found on the PLMN of the first roaming operator, a registration request #1 is sent to the access network device 1, where the registration request #1 is used to request registration with the first network of the PLMN of the first roaming operator.

[0174] The registration request #1 here may correspond to the first registration request mentioned above.

[0175] In step S613, in response to the registration request #1, the access network device 1 sends a registration rejection message #1, and the terminal device receives the registration rejection message #1.

[0176] Registration Reject Message #1 is used to indicate that the terminal device has failed to successfully register with the first network of the PLMN of the first roaming operator and to instruct the terminal device to search for a second network with a lower network standard than the first network on the PLMN of the first roaming operator. Exemplarily, Registration Reject Message #1 includes Cause Value #111, Cause Value #16, or Cause Value #17.

[0177] In step S614, in response to the registration rejection message #1, the terminal device prohibits the use of the first network of the PLMN of the first roaming operator within the second preset duration, and searches for the first network on the PLMNs of other roaming operators within the first preset duration.

[0178] In step S615, the terminal device determines whether the first network is searched within the first preset time period.

[0179] In other words, the terminal device determines whether it has searched for a 4G network before the first preset time expires.

[0180] If the first network is found within the first preset time period, the terminal device executes step S620.

[0181] When the first network is not found within the first preset time period, there are two situations. The terminal device can choose one of the two situations to execute. In the first case, the terminal device executes step S641, or in the second case, the terminal device executes step S642. The purpose is to search for a second network with a network standard lower than the first network when the first network is not found.

[0182] In step S620, when the terminal device searches for the first network on the PLMN operated by the second roaming operator of another roaming operator, it sends a registration request #2 to the access network device 2. The registration request #2 is used to request registration to the first network of the PLMN of the second roaming operator.

[0183] The registration request #2 here may correspond to the second registration request above.

[0184] It should be understood that access network device 1 and access network device 2 can be the same device or different devices, depending on whether the first roaming operator and the second roaming operator share the same access network device. If the first roaming operator and the second roaming operator share the same access network device, access network device 1 and access network device 2 can be the same device, and the terminal device will send registration request #1 and registration request #2 to the same access network device. If the first roaming operator and the second roaming operator do not share the same access network device, different access network devices support their respective roaming operators. Access network device 1 and access network device 2 are different devices, and the terminal device will send registration request #1 and registration request #2 to access network device 1 and access network device 2, respectively, supported by the first roaming operator and the second roaming operator.

[0185] In step S621, the terminal device determines whether the registration is successful.

[0186] In this step, the terminal device determines whether the terminal device is successfully registered with the first network of the PLMN of the second roaming operator.

[0187] If the terminal device is successfully registered, the terminal device communicates through the first network of the second roaming operator until the second preset time period times out, and then executes step S660.

[0188] If the terminal device fails to register successfully, step S623 and step S631 or step S632 are executed to determine whether the first preset time has timed out, and to execute different steps if it has timed out or not.

[0189] The terminal device determines whether the registration is successful based on the feedback from the access network device. If the terminal device receives a registration rejection message #2 for registration request #2, it means that the registration is unsuccessful; if the terminal device receives a registration success message for registration request #2d, it means that the registration is successful.

[0190] In step S623 , when the terminal device fails to successfully register with the first network of the PLMN of the second roaming operator, the terminal device determines whether the first preset duration has timed out.

[0191] If the first preset time period times out, the terminal device executes step S632; if the first preset time period does not time out, the terminal device executes step S631.

[0192] In step S631, if the terminal device fails to successfully register with the first network of the PLMN of the second roaming operator and the first preset time period has not timed out, the terminal device continues to search for the first network on the PLMNs of other roaming operators except the second roaming operator within the first preset time period.

[0193] In this step, during the process of searching for the first network, step S615 and subsequent related steps are repeatedly executed to try to register with the first network of a higher standard or the second network of a lower standard.

[0194] Specifically, within a first preset duration, if the terminal device searches for the first network on the PLMN of a roaming operator other than the second roaming operator among other roaming operators, for example, a third roaming operator, the terminal device initiates a new registration request. If the registration is successful, the terminal device uses the first network of the PLMN of the third roaming operator for communication. If the first network of the PLMN of the third roaming operator is not successfully registered and the first preset duration has not expired, the terminal device continues to search for the first network on the PLMNs of roaming operators other than the second and third roaming operators among other roaming operators until the first network is found within the first preset duration or a second network of a lower standard is searched after the first preset duration expires.

[0195] Of course, if there is only the first roaming operator and no other roaming operators among the other roaming operators, this step is skipped, and the terminal device directly searches for the second network of the lower standard.

[0196] In the above embodiment, when the terminal device fails to successfully register with the first network of the PLMN of the second roaming operator and the first preset time period has not timed out, the terminal device continues to search for the first network on the PLMNs of other roaming operators except the second roaming operator within the first preset time period, which can increase the chance of the terminal device searching for the first network, thereby increasing the chance of registering with the first network and improving the user experience.

[0197] In step S632, when the terminal device fails to successfully register with the first network of the PLMN of the second roaming operator and the first preset time period times out, the terminal device searches for a second network with a network standard lower than the first network on the PLMN of at least one roaming operator in the roaming area.

[0198] That is, if the terminal device fails to successfully register with the first network of the second roaming operator's PLMN after the first preset duration expires, to expedite network access, the terminal device no longer searches for the first network, but instead searches for a second network of a lower standard on the PLMN of at least one roaming operator in the roaming location to register with the second network. If a second network of a lower standard is found, step S650 is executed to register with the second network of the lower standard. It will be understood that in this case, it takes a certain amount of time for the terminal device to search for the first network of the second roaming operator, and the terminal device is likely to fail to search for the first network on PLMNs of roaming operators other than the second roaming operator. Therefore, searching for a second network of a lower standard after the first preset duration expires increases the probability of the terminal device gaining network access as quickly as possible.

[0199] In some embodiments, in the step where the terminal device searches for a second network with a network standard lower than the first network on the PLMN of at least one roaming operator in the roaming area, the terminal device preferentially searches for the second network with a network standard lower than the first network on the PLMN of the first roaming operator.

[0200] For a detailed description of the terminal device searching for a second network with a network standard lower than the first network on the PLMN of at least one roaming operator in the roaming area, please refer to the above related description and will not be repeated here.

[0201] In step S641, when the first preset time has not timed out and the first network is not found on the PLMN of any roaming operator in other roaming operators, before the first preset time has timed out, the terminal device searches for a second network with a network standard lower than the first network on the PLMN of at least one roaming operator in the roaming area.

[0202] That is, if the terminal device has traversed all roaming operators in other roaming areas before the first preset duration expires, and the traversal result is that the first network has not been found on any roaming operator's PLMN. In this case, the terminal device does not need to wait for the first preset duration to expire before searching for the second network of a lower standard. Instead, the terminal device ends the search duration (i.e., the first preset duration) in advance and searches for the second network of a lower standard on the PLMN of at least one roaming operator in the roaming area before the first preset duration expires. In this way, if it is confirmed that the first network has not been found on any roaming operator's PLMN, the terminal device ends the search duration in advance so that the second network of a lower standard can be searched on the PLMN of at least one roaming operator in the roaming area in advance. This reduces unnecessary search time, allows the terminal device to search for other networks as quickly as possible, and access the network as soon as possible, and improves the user experience.

[0203] It should be understood that "the first preset duration has not timed out" means a time that does not exceed the end time of the first preset duration, and "before the first preset duration times out" means a time before the end time of the first preset duration exceeds.

[0204] In some embodiments, in the step where the terminal device searches for a second network with a network standard lower than the first network on the PLMN of at least one roaming operator in the roaming area, the terminal device preferentially searches for the second network with a network standard lower than the first network on the PLMN of the first roaming operator.

[0205] For a detailed description of the terminal device searching for a second network with a network standard lower than the first network on the PLMN of at least one roaming operator in the roaming area, please refer to the above related description and will not be repeated here.

[0206] In combination with the first timer for the first preset duration defined above, in implementation, the terminal device starts the first timer and searches for the first network on the PLMNs of other roaming operators within the duration of the first timer; if the first timer has not timed out and the first network is not found on the PLMNs of any of the other roaming operators, the terminal device turns off the first timer in advance; after turning off the first timer, the terminal device searches for a second network with a network standard lower than the first network on the PLMNs of at least one roaming operator in the roaming area.

[0207] It should be understood that the early closing of the first timer described here means closing the timer before the first timer expires. In this way, after closing the first timer, the terminal device can search for the second network with a low standard in advance before the first preset time period expires.

[0208] In step S642, when the first preset time expires and the first network has not been searched on the PLMN of other roaming operators, the terminal device searches for a second network with a network standard lower than the first network on the PLMN of at least one roaming operator in the roaming area.

[0209] In this step, when the first preset time has expired, the terminal device has not searched for the first network on the PLMN of other roaming operators, but the first preset time has expired. In this case, the terminal device no longer searches for the first network, but searches for a low-standard second network on the PLMN of at least one roaming operator in the roaming area.

[0210] In some embodiments, in the step where the terminal device searches for a second network with a network standard lower than the first network on the PLMN of at least one roaming operator in the roaming area, the terminal device preferentially searches for the second network with a network standard lower than the first network on the PLMN of the first roaming operator.

[0211] For a detailed description of the terminal device searching for a second network with a network standard lower than the first network on the PLMN of at least one roaming operator in the roaming area, please refer to the above related description and will not be repeated here.

[0212] In step S650, when the terminal device searches for a second network with a lower network standard than the first network on any roaming operator's PLMN, it sends a registration request #3 to request that the terminal device be registered with the second network of the roaming operator's PLMN.

[0213] It should be understood that the "any roaming operator" herein refers to any one of the at least one roaming operator described above. In an embodiment where the terminal device preferentially searches for the second network on the PLMN of the first roaming operator, if the terminal device searches for the second network on the PLMN of the first roaming operator, then the "any roaming operator" is the first roaming operator.

[0214] In step S660, when the second preset time period expires, the terminal device releases the disabled state of the first network of the PLMN of the first roaming operator.

[0215] In this way, after the disabled state of the first network of the first roaming operator's PLMN is lifted, the terminal device can return to the first network through a reselection or redirection process to re-search and attempt to register with the first network. If registration fails, the terminal device continues to search the first network or the second network to try to connect the terminal device to the network. If registration is successful, the terminal device will reside on the first network. In this way, if the terminal device ultimately fails to successfully register with the first network, after the disabled state of the first network of the first roaming operator's PLMN is lifted, the terminal device will have the opportunity to return to the first network of the higher standard and attempt to register with the first network, thereby maximizing the user experience.

[0216] FIG7 is a schematic flowchart of a network registration method 700 in a roaming scenario provided by an embodiment of the present application.

[0217] In method 700, a specific embodiment is illustrated by taking an example in which the first network is a 4G network and the second network is a 3G network or a 2G network, and an example in which roaming operator #1 is a first roaming operator, roaming operator #2 is a second roaming operator, timer #1 is a first timer, and timer #2 is a second timer. In combination with the above description, similar or identical contents in method 700 are briefly described and are not repeated here.

[0218] In method 700, in a roaming scenario, the terminal device is located in the roaming area, is powered on and searches for a network on the PLMN of the roaming area operator in the roaming area.

[0219] In step S711, the terminal device searches for a 4G network on the PLMN of the roaming operator #1.

[0220] In step S712, when a 4G network is found on the PLMN of the roaming operator #1, a registration request #1 is sent to the access network device 1. The registration request #1 is used to request registration to the 4G network of the PLMN of the roaming operator #1.

[0221] In step S713, in response to the registration request #1, the access network device 1 sends a registration rejection message #1, and the terminal device receives the registration rejection message #1.

[0222] In step S714, the terminal device starts timer #2 and prohibits the use of the 4G network of the PLMN of the roaming operator #2 during the duration of timer #2. The duration of timer #2 is the second preset duration.

[0223] In step S715, the terminal device starts timer #1. The duration of timer #1 is a first preset duration, which is shorter than a second preset duration.

[0224] In the above steps, there is no limitation on the order of step S714 and step S715, and step S714 and step S715 can be executed simultaneously, that is, the terminal device can start timer #2 and timer #1 at the same time; or, step S714 can be executed before step S715, that is, the terminal device starts timer #2 first and then starts timer #1.

[0225] In step S716, the terminal device searches for a 4G network on the PLMN of other roaming operators within the duration of timer #1.

[0226] In step S717, the terminal device determines whether a 4G network is found within the duration of timer #1.

[0227] In other words, the terminal device determines whether a 4G network is found before timer #1 times out.

[0228] If a 4G network is found within the duration of timer #1, the terminal device executes step S720; if a 4G network is not found within the duration of timer #1, the terminal device executes step S741 or step S742, with the purpose of searching for a 3G network or a 2G network with a network standard lower than that of a 4G network if a 4G network is not found.

[0229] In step S720, when the terminal device searches for a 4G network on the PLMN of roaming operator #2 of other roaming operators, it sends a registration request #2 to access network device 2. Registration request #2 is used to request registration to the 4G network of the PLMN of roaming operator #2.

[0230] In step S721, the terminal device determines whether the registration is successful.

[0231] It should be understood that when the terminal device determines whether the registration is successful, what is determined is whether the terminal device is successfully registered to the 4G network of the PLMN of the roaming operator #2.

[0232] If the terminal device is successfully registered, the terminal device communicates through the 4G network of the roaming operator #2 until timer #2 times out, and then executes step S760.

[0233] If the terminal device fails to register successfully, step S723 and step S731 or step S732 are executed to determine whether timer #1 has timed out, and to execute different steps if it has timed out or not.

[0234] The terminal device determines whether the registration is successful based on the information fed back by the access network device. If the terminal device receives the registration rejection message #2, it means that the registration is unsuccessful; if the terminal device receives the registration success message, it means that the registration is successful.

[0235] In step S723, the terminal device determines whether timer #1 has timed out.

[0236] If timer #1 times out, the terminal device executes step S732; if timer #1 does not time out, the terminal device executes step S731.

[0237] In step S731, if the terminal device fails to successfully register to the 4G network of the PLMN of roaming operator #2 and timer #1 has not expired, the terminal device continues to search for 4G networks on the PLMNs of other roaming operators except roaming operator #2 within the duration of timer #1.

[0238] In the process of searching for a 4G network, step S717 and subsequent related steps are repeatedly performed, and finally an attempt is made to register on a high-standard 4G network, or an attempt is made to register on a low-standard 3G network or 2G network. For a detailed description of this step, please refer to the description of step S631 in method 600, which will not be repeated here.

[0239] In step S732, if the terminal device fails to successfully register with the 4G network of the PLMN of the roaming operator #2 and timer #1 times out, the terminal device searches for a 3G network or a 2G network on the PLMN of at least one roaming operator in the roaming area.

[0240] For a detailed description of this step, please refer to the relevant description of step S632 in method 600, which will not be repeated here.

[0241] In step S741, if timer #1 has not timed out and no 4G network is searched on the PLMN of any roaming operator in other roaming operators, timer #1 is closed in advance; after closing timer #1, the terminal device searches for a 3G network or a 2G network on the PLMN of at least one roaming operator in the roaming area.

[0242] It should be understood that the early closing of timer #1 described here means closing the timer before timer #1 expires. In this way, after closing timer #1, the terminal device can search for the 3G network or 2G network in advance before the first preset time period expires.

[0243] For a detailed description of this step, please refer to the relevant description of step S641 in method 600, which will not be repeated here.

[0244] In step S742, when timer #1 times out and no 4G network has been found on the PLMN of other roaming operators, the terminal device searches for a 3G network or a 2G network on the PLMN of at least one roaming operator in the roaming area.

[0245] For a detailed description of this step, please refer to the relevant description of step S642 in method 600, which will not be repeated here.

[0246] In step S750, when the terminal device searches for a 3G network or a 2G network on any roaming operator's PLMN, it sends a registration request #3 to request that the terminal device be registered with the 3G network or the 2G network of the roaming operator's PLMN.

[0247] It should be understood that the "any roaming operator" herein refers to any one of the at least one roaming operator mentioned above. In an embodiment where the terminal device preferentially searches for a lower-standard network on the PLMN of roaming operator #1, if the terminal device searches for a 3G network or a 2G network on the PLMN of roaming operator #1, then the "any roaming operator" is roaming operator #1.

[0248] In step S760, when timer #2 times out, the terminal device releases the disabled state of the 4G network of the PLMN of the roaming operator #1.

[0249] It should be noted again that the size of the serial numbers of the steps in the above method embodiments does not mean the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of this application.

[0250] Above, in combination with Figures 1 to 7, the network registration method in the roaming scenario provided by the embodiment of the present application is described in detail. Below, in combination with Figures 8 to 9, the terminal device provided according to the embodiment of the present application is described in detail.

[0251] FIG8 is an exemplary block diagram of a terminal device 800 provided in an embodiment of the present application. The terminal device 800 includes a processing unit 810 and a transceiver unit 820 .

[0252] The transceiver unit 820 is configured to: when a first network is searched for on a public land mobile network PLMN of a first roaming operator in a roaming area, send a first registration request, wherein the first registration request is used to request registration of the terminal device with the first network of the PLMN of the first roaming operator;

[0253] The transceiver unit 820 is further configured to: receive a registration rejection message in response to the first registration request, where the registration rejection message is used to indicate that the terminal device has not successfully registered with the first network of the PLMN of the first roaming operator, and is used to instruct the terminal device to search for a second network with a network standard lower than that of the first network on the PLMN of the first roaming operator;

[0254] The processing unit 810 is configured to: in response to the registration rejection message, search for the first network on PLMNs of other roaming operators in the roaming region except the first roaming operator;

[0255] The transceiver unit 820 is further configured to, when the first network is found on the PLMN of a second roaming operator among the other roaming operators, send a second registration request to register the terminal device with the first network of the PLMN of the second roaming operator.

[0256] Optionally, the processing unit 810 is specifically configured to: in response to the registration rejection message, search for the first network on the PLMN of the other roaming operator within a first preset time period.

[0257] Optionally, the processing unit 810 is further used to: when the terminal device fails to successfully register to the first network of the PLMN of the second roaming operator and the first preset time has not timed out, continue searching for the first network on the PLMNs of the other roaming operators except the second roaming operator within the first preset time.

[0258] Optionally, the processing unit 810 is further used to: when the terminal device fails to successfully register with the first network of the PLMN of the second roaming operator and the first preset time period times out, search for a second network with a network standard lower than that of the first network on the PLMN of at least one roaming operator in the roaming area.

[0259] Optionally, the processing unit 810 is further configured to: when the first preset duration has not timed out and the first network is not found on the PLMN of any roaming operator among the other roaming operators, before the first preset duration times out, search for a second network having a lower network standard than the first network on the PLMN of at least one roaming operator in the roaming area.

[0260] Optionally, the processing unit 810 is further configured to: when the first preset time expires and the first network has not been searched on the PLMNs of the other roaming operators, search for a second network having a lower network standard than the first network on the PLMNs of at least one roaming operator in the roaming area.

[0261] Optionally, the processing unit 810 is further configured to: when the first network is not found on the PLMNs of at least some of the other roaming operators, search for a second network having a lower network standard than the first network on the PLMNs of at least one roaming operator in the roaming area.

[0262] Optionally, the processing unit 810 is further configured to: when the terminal device fails to successfully register with the first network of the PLMN of the second roaming operator, search for a second network having a lower network standard than the first network on the PLMN of at least one roaming operator in the roaming area.

[0263] Optionally, the processing unit 810 is specifically configured to: preferentially search, on the PLMN of the first roaming operator, for the second network having a lower network standard than that of the first network.

[0264] Optionally, the processing unit 810 is specifically used to: in response to the registration rejection message, prohibit the use of the first network of the PLMN of the first roaming operator within a second preset time period, and search for the first network on the PLMNs of other roaming operators within the first preset time period, and the first preset time period is less than the second preset time period.

[0265] Optionally, the processing unit 810 is specifically configured to: in response to the registration rejection message, start a timer, where the duration of the timer is the first preset duration;

[0266] Searching for the first network on the PLMN of the other roaming operator within the duration of the timer.

[0267] Optionally, the registration rejection message includes any one of the following reason values: reason value #111, reason value #16, and reason value #17.

[0268] Optionally, the first network is a 5G network or a 4G network.

[0269] It should be understood that the processing unit 810 can be used to execute the various steps performed by the terminal device in methods 400, 600 and 700. For specific descriptions, please refer to the relevant descriptions above and will not be repeated here.

[0270] It should be understood that the terminal device 800 herein is embodied in the form of a functional unit. The term "unit" herein may refer to an application specific integrated circuit (ASIC), an electronic circuit, a processor (e.g., a shared processor, a dedicated processor, or a group processor, etc.) and memory for executing one or more software or firmware programs, a combined logic circuit, and / or other suitable components that support the described functionality.

[0271] In an embodiment of the present application, the terminal device in FIG8 may also be a chip or a chip system, for example, a system on chip (SoC).

[0272] FIG9 is a schematic structural diagram of a terminal device 900 provided in an embodiment of the present application. The terminal device 900 is used to execute the corresponding steps and / or processes in the above method embodiment.

[0273] The terminal device 900 includes a processor 910, a transceiver 920, and a memory 930. The terminal device 900 may correspond to the terminal device 110 shown in FIG. 2 above, where the processor 910 may correspond to the processor 111 of the terminal device 110, and the transceiver 920 may integrate the function of the antenna 1 of the terminal device 110.

[0274] The processor 910, transceiver 920, and memory 930 communicate with each other via an internal connection path, and the processor 910 can implement the functions of the processor 910 in various possible implementations of the terminal device 900. The memory 930 is used to store instructions, and the processor 910 is used to execute the instructions stored in the memory 930. In other words, the processor 910 can call these stored instructions to implement the functions of the processor 910 in the terminal device 900.

[0275] Optionally, the memory 930 may include a read-only memory and a random access memory, and provide instructions and data to the processor. A portion of the memory may also include non-volatile random access memory. For example, the memory may also store device type information. The processor 910 may be configured to execute instructions stored in the memory, and when the processor 910 executes the instructions stored in the memory, the processor 910 is configured to perform the various steps and / or processes of the above-described method embodiment corresponding to the terminal device.

[0276] The transceiver 920 is configured to: when a first network is searched for on a public land mobile network PLMN of a first roaming operator in a roaming area, send a first registration request, wherein the first registration request is used to request registration of the terminal device with the first network of the PLMN of the first roaming operator;

[0277] The transceiver 920 is further configured to: receive a registration rejection message in response to the first registration request, where the registration rejection message is used to indicate that the terminal device has not successfully registered with the first network of the PLMN of the first roaming operator, and is used to instruct the terminal device to search for a second network having a network standard lower than that of the first network on the PLMN of the first roaming operator;

[0278] The processor 910 is configured to: in response to the registration rejection message, search for the first network on PLMNs of other roaming operators in the roaming region except the first roaming operator;

[0279] The transceiver 920 is further configured to, when the first network is searched for on the PLMN of a second roaming operator among the other roaming operators, send a second registration request to register the terminal device with the first network of the PLMN of the second roaming operator.

[0280] It should be understood that the specific process of each device executing the corresponding steps in the above methods has been described in detail in the above method embodiments, and for the sake of brevity, it will not be repeated here.

[0281] It should be understood that in the embodiments of the present application, the processor of the above-mentioned device may be a central processing unit (CPU), and the processor may also be other general-purpose processors, digital signal processors (DSPs), application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs) or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. The general-purpose processor may be a microprocessor or any conventional processor, etc.

[0282] During implementation, each step of the above method can be completed by an integrated logic circuit of hardware in a processor or by instructions in the form of software. The steps of the method disclosed in conjunction with the embodiments of the present application can be directly embodied as being executed by a hardware processor, or can be executed by a combination of hardware and software units in the processor. The software unit can be located in a storage medium mature in the art, such as a random access memory, a flash memory, a read-only memory, a programmable read-only memory, or an electrically erasable programmable memory, a register, etc. The storage medium is located in a memory, and the processor executes the instructions in the memory, and in combination with its hardware, completes the steps of the above method. To avoid repetition, a detailed description is not given here.

[0283] The present application provides a computer program product that, when executed on a terminal device, enables the terminal device to execute the technical solution in the above embodiment. The implementation principle and technical effects are similar to those of the above method-related embodiments and will not be described in detail here.

[0284] The embodiment of the present application provides a readable storage medium, which contains instructions. When the instructions are executed on a terminal device, the terminal device executes the technical solution of the above embodiment. The implementation principle and technical effect are similar and will not be repeated here.

[0285] The present application provides a chip for executing instructions. When the chip is running, the technical solution of the above embodiment is executed. The implementation principle and technical effect are similar and will not be described here.

[0286] In the above embodiments, all or part of the embodiments may be implemented by software, hardware, firmware, or any combination thereof. When implemented using software, all or part of the embodiments may be implemented in the form of a computer program product. The computer program product includes one or more computer instructions. When the computer instructions are loaded and executed on a computer, all or part of the processes or functions described in the embodiments of the present application are generated. The computer may be a general-purpose computer, a special-purpose computer, a computer network, or other programmable device. The computer instructions may be stored in a computer-readable storage medium or transmitted from one computer-readable storage medium to another computer-readable storage medium. For example, the computer instructions may be transmitted from one website, computer, server, or data center to another website, computer, server, or data center via a wired (e.g., coaxial cable, optical fiber, digital subscriber line (DSL)) or wireless (e.g., infrared, wireless, microwave, etc.) method. The computer-readable storage medium may be any available medium that a computer can access or a data storage device such as a server or data center that includes one or more available media integrated therein. The available medium may be a magnetic medium (eg, a floppy disk, a hard disk, a magnetic tape), an optical medium (eg, a high-density digital video disc (DVD)), or a semiconductor medium (eg, a solid state disk (SSD)).

[0287] It should be understood that the “embodiment” mentioned throughout the specification means that the specific features, structures or characteristics related to the embodiment are included in at least one embodiment of the present application. Therefore, the various embodiments in the entire specification do not necessarily refer to the same embodiment. In addition, these specific features, structures or characteristics can be combined in one or more embodiments in any suitable manner. It should be understood that in the various embodiments of the present application, the size of the sequence number of the above-mentioned processes does not mean the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiment of the present application.

[0288] It should also be understood that in this application, "when", "if" and "if" all mean that the UE or base station will take corresponding measures under certain objective circumstances. It does not limit the time, and does not require the UE or base station to take judgment actions when implementing it, nor does it mean that there are other limitations.

[0289] Those skilled in the art will understand that the various numerical numbers such as first and second involved in this application are only for the convenience of description and are not used to limit the scope of the embodiments of this application, and also indicate the order of precedence.

[0290] In this application, elements expressed in the singular are intended to mean "one or more" rather than "one and only one" unless otherwise specified. In this application, unless otherwise specified, "at least one" is intended to mean "one or more" and "a plurality" is intended to mean "two or more."

[0291] The term "and / or" in this article is merely a description of the association relationship of associated objects, indicating that there can be three relationships. For example, A and / or B can mean: A exists alone, A and B exist at the same time, and B exists alone. A can be singular or plural, and B can be singular or plural.

[0292] In this document, the term "at least one of..." or "at least one of..." means all or any combination of the listed items. For example, "at least one of A, B and C" may mean: A exists alone, B exists alone, C exists alone, A and B exist at the same time, B and C exist at the same time, and A, B and C exist at the same time. A may be singular or plural, B may be singular or plural, and C may be singular or plural.

[0293] Those skilled in the art will appreciate that the units and algorithm steps of each example described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are performed in hardware or software depends on the specific application and design constraints of the technical solution. Professional and technical personnel can use different methods to implement the described functions for each specific application, but such implementation should not be considered beyond the scope of this application.

[0294] Those skilled in the art will clearly understand that, for the convenience and brevity of description, the specific working processes of the above-described systems, devices and units can refer to the corresponding processes in the aforementioned method embodiments and will not be repeated here.

[0295] In the several embodiments provided in this application, it should be understood that the disclosed systems, devices and methods can be implemented in other ways. For example, the device embodiments described above are merely schematic. For example, the division of the units is merely a logical function division. In actual implementation, there may be other division methods, such as multiple units or components can be combined or integrated into another system, or some features can be ignored or not executed. Another point is that the mutual coupling or direct coupling or communication connection shown or discussed can be through some interfaces, indirect coupling or communication connection of devices or units, which can be electrical, mechanical or other forms.

[0296] The units described as separate components may or may not be physically separate, and the components shown as units may or may not be physical units, that is, they may be located in one place or distributed across multiple network units. Some or all of these units may be selected to achieve the purpose of this embodiment according to actual needs.

[0297] In addition, each functional unit in each embodiment of the present application may be integrated into one processing unit, or each unit may exist physically separately, or two or more units may be integrated into one unit.

[0298] If the functions are implemented in the form of software functional units and sold or used as independent products, they can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present application, or the part that contributes to the prior art, or the part of the technical solution, can be embodied in the form of a software product. The computer software product is stored in a storage medium and includes several instructions for enabling a computer device (which can be a personal computer, a server, or a network device, etc.) to execute all or part of the steps of the method described in each embodiment of the present application. The aforementioned storage medium includes various media that can store program codes, such as a USB flash drive, a mobile hard disk, a read-only memory (ROM), a random access memory (RAM), a magnetic disk or an optical disk.

[0299] The same or similar parts between the various embodiments in this application can refer to each other. In the various embodiments in this application, and the various implementation methods / implementation methods / implementation methods in each embodiment, if there is no special explanation and logical conflict, the terms and / or descriptions between different embodiments and the various implementation methods / implementation methods / implementation methods in each embodiment are consistent and can be referenced to each other. The technical features in different embodiments and the various implementation methods / implementation methods / implementation methods in each embodiment can be combined to form new embodiments, implementation methods, implementation methods, or implementation methods according to their inherent logical relationships. The above-described implementation methods of this application do not constitute a limitation on the scope of protection of this application.

[0300] The above is only a specific embodiment of the present application, but the scope of protection of the present application is not limited thereto. Any technician familiar with the technical field can easily think of changes or replacements within the technical scope disclosed in the present application, which should be included in the scope of protection of the present application. Therefore, the scope of protection of the present application should be based on the scope of protection of the claims. In short, the above is only a preferred embodiment of the technical solution of the present application, and is not used to limit the scope of protection of the present application. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present application should be included in the scope of protection of the present application.

Claims

1. A network registration method in a roaming scenario, applied to a terminal device, characterized in that: include: In the case where a first network is searched for on a public land mobile network PLMN of a first roaming operator in a roaming area, sending a first registration request, wherein the first registration request is used to request that a terminal device be registered to the first network of the PLMN of the first roaming operator; receiving a registration rejection message in response to the first registration request, the registration rejection message being used to indicate that the terminal device has not successfully registered with the first network of the PLMN of the first roaming operator, and being used to instruct the terminal device to search for a second network with a network standard lower than that of the first network on the PLMN of the first roaming operator; In response to the registration rejection message, searching for the first network on PLMNs of other roaming operators in the roaming area except the first roaming operator; When the first network is searched for on the PLMN of a second roaming operator among the other roaming operators, a second registration request is sent to register the terminal device with the first network of the PLMN of the second roaming operator.

2. The network registration method according to claim 1, characterized in that: In response to the registration rejection message, searching for the first network on PLMNs of other roaming operators in the roaming area except the first roaming operator, comprises: In response to the registration rejection message, searching for the first network on the PLMN of the other roaming operator within a first preset time period.

3. The network registration method according to claim 2, characterized in that: The method further comprises: When the terminal device fails to successfully register with the first network of the PLMN of the second roaming operator and the first preset time period has not timed out, continue searching for the first network on the PLMNs of roaming operators among other roaming operators except the second roaming operator within the first preset time period.

4. The network registration method according to claim 2 or 3, characterized in that: The method further comprises: When the terminal device fails to successfully register with the first network of the PLMN of the second roaming operator and the first preset time period times out, a second network with a network standard lower than that of the first network is searched on the PLMN of at least one roaming operator in the roaming area.

5. The network registration method according to any one of claims 2 to 4, characterized in that: The method further comprises: When the first preset time has not timed out and the first network has not been searched on the PLMN of any roaming operator among the other roaming operators, before the first preset time has timed out, a second network with a network standard lower than that of the first network is searched on the PLMN of at least one roaming operator in the roaming area.

6. The network registration method according to any one of claims 2 to 5, characterized in that: The method further comprises: When the first preset time expires and the first network has not been searched on the PLMNs of the other roaming operators, a second network with a network standard lower than that of the first network is searched on the PLMNs of at least one roaming operator in the roaming area.

7. The network registration method according to any one of claims 1 to 6, characterized in that: The method further comprises: When the first network is not found on the PLMNs of at least some of the other roaming operators, a second network having a lower network standard than the first network is searched on the PLMNs of at least one roaming operator in the roaming area.

8. The network registration method according to any one of claims 1 to 7, characterized in that: The method further comprises: In the case that the terminal device fails to successfully register with the first network of the PLMN of the second roaming operator, a second network having a network standard lower than that of the first network is searched on the PLMN of at least one roaming operator in the roaming area.

9. The network registration method according to any one of claims 4 to 8, characterized in that: The searching, on the PLMN of at least one roaming operator in the roaming location, for a second network having a network standard lower than that of the first network comprises: The second network having a network standard lower than that of the first network is preferentially searched on the PLMN of the first roaming operator.

10. The network registration method according to any one of claims 2 to 6, characterized in that: In response to the registration rejection message, searching for the first network on the PLMN of the other roaming operator within a first preset time period includes: In response to the registration rejection message, the use of the first network of the PLMN of the first roaming operator is prohibited within a second preset time period, and the first network is searched on the PLMNs of the other roaming operators within the first preset time period, and the first preset time period is less than the second preset time period.

11. The network registration method according to any one of claims 2 to 10, characterized in that: In response to the registration rejection message, searching for the first network on the PLMN of the other roaming operator within a first preset time period includes: In response to the registration rejection message, start a timer, where the duration of the timer is the first preset duration; The first network is searched on the PLMN of the other roaming operator within the duration of the timer.

12. The network registration method according to any one of claims 1 to 11, characterized in that: The registration rejection message includes any one of the following reason values: reason value #111, reason value #16, reason value #17.

13. The network registration method according to any one of claims 1 to 12, characterized in that: The first network is a 5G network or a 4G network.

14. A terminal device, characterized in that: include: Memory, for storing computer instructions; A processor, configured to call the computer instructions stored in the memory to execute the method according to any one of claims 1 to 13.

15. A computer-readable storage medium, characterized in that: Used to store computer instructions, wherein the computer instructions are used to implement the method according to any one of claims 1 to 13.

16. A chip, characterized in that: The chip comprises: Memory: used to store instructions; A processor, configured to call and execute the instructions from the memory, so that a communication device equipped with the chip system executes the method as claimed in any one of claims 1 to 13.

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