WO2025213860A1 - Network selection method, terminal device, computer-readable storage medium and chip - Google Patents

Abstract

The present application relates to the technical field of communications. Provided are a network selection method, a terminal device, a computer-readable storage medium and a chip. The method is applied to a terminal device, wherein a SIM card installed in the terminal device supports a first VPLMN and a second VPLMN, which are different from each other. The method comprises: successfully performing registration with a first network of a first network standard of a first VPLMN; detecting that the first network cannot provide a service to a terminal device, and searching for a second network of a second network standard of a second VPLMN, wherein the first network standard is the same as the second network standard, or the second network standard is higher than the first network standard; and after the second network is found, performing registration with the second network. In the technical solutions provided in the embodiments of the present application, after being disconnected from a network in a roaming scenario, a terminal device can be preferentially connected to high-standard networks of other VPLMNs, so as to avoid the downgrade of the network of the terminal device from a higher standard to a lower standard as much as possible, thereby ensuring the communication quality of the terminal device, and improving the user experience.

Description

Network selection method, terminal device, computer-readable storage medium, and chip

This application claims priority to the Chinese patent application filed with the State Intellectual Property Office on April 10, 2024, with application number 202410430510.6 and application name “Network selection method, terminal device, computer-readable storage medium and chip”, the entire contents of which are incorporated by reference into this application.

Technical Field

The present application relates to the field of communication technology, and in particular to a network selection method, terminal equipment, computer-readable storage medium, and chip.

Background Art

Currently, terminal devices need to connect to a roaming network in the roaming area to use network services such as voice, data, and multimedia. The roaming network is the visited public land mobile network (VPLMN).

Terminal devices typically prioritize registering with the higher-standard VPLMN network and, after successful registration, mark the VPLMN as a registered public land mobile network (RPLMN). Later, if the terminal device detects that the higher-standard RPLMN network is temporarily unavailable, it will automatically fall back to the lower-standard RPLMN network. Understandably, the change from a higher-standard network to a lower-standard network prevents the terminal device from using the higher-standard high-speed and high-quality voice services, resulting in poor communication quality and a significant impact on the user experience.

Summary of the Invention

The present application provides a network selection method, a terminal device, a computer-readable storage medium, and a chip, which are used to solve the problem in the prior art that the call quality of the terminal device may deteriorate after being disconnected from the network in a random field.

To achieve the above objectives, this application adopts the following technical solutions:

In a first aspect, an embodiment of the present application provides a network selection method, which is applied to a terminal device, wherein the terminal is equipped with a user identification module SIM card, and the SIM card supports a first VPLMN and a second VPLMN. The method specifically includes: successfully registering a first network of a first network standard of the first VPLMN; detecting that the first network cannot provide services to the terminal device, and searching for a second network of a second network standard of the second VPLMN; wherein the first network standard is the same as the second network standard, or the second network standard is higher than the first network standard; after searching for the second network, registering the second network.

Through the network selection method provided in the embodiment of the present application, after the terminal device is disconnected from the network in a roaming scenario, it can preferentially connect to the high-standard network of other VPLMNs, thereby avoiding the terminal device's network from dropping from a high standard to a low standard as much as possible, thereby ensuring the communication quality of the terminal device and improving the user experience.

In some embodiments, the terminal device detects that the first network cannot provide services to the terminal device, including: under the first network, the terminal device cannot search for a cell that meets the registration conditions; or the terminal device receives a first indication message sent by the network device, and the first indication message is used to indicate that the terminal device cannot temporarily use the first network.

In other words, the terminal device may determine whether the first network can provide services by itself, or may determine whether the first network can provide services based on a notification from the network device.

In some embodiments, the coverage area of the first network includes different and partially overlapping first location areas and second location areas; then, the terminal device successfully registers with the first network of the first network standard of the first VPLMN, including: the terminal device successfully registers with the first cell of the first location area.

In some embodiments, after searching for a second network of the second network standard of the second VPLMN, the terminal device registers the second network, specifically including: if the terminal device does not search for a second cell that meets the registration conditions in the second location area, searching for a second network of the second network standard of the second VPLMN; and, after searching for the second network, registering with the second network. Alternatively, if the terminal device searches for a second cell that meets the registration conditions in the second location area and registration with the second cell fails, searching for a second network of the second network standard of the second VPLMN; and, after searching for the second network, registering with the second network.

Through the network selection method provided in this embodiment, the terminal device can continue to try to register the first network of the RPLMN first network standard in other location areas to ensure that the terminal device still resides on the first network as much as possible, avoid the terminal device from continuing to search and switch PLMN, and improve the network recovery speed of the terminal device.

In some embodiments, after the terminal device successfully registers the first network of the first network standard of the first VPLMN, the method further includes: marking the first VPLMN as RPLMN; and after failing to register the second network, registering a third network of the third network standard of RPLMN; wherein the third network standard is lower than the first network standard.

Through the network selection method provided in this embodiment, when other VPLMNs cannot guarantee that the network standard of the network selected by the terminal device will not be reduced, the terminal device will preferably select a network with a lower RPLMN standard (such as 3G) to avoid the terminal device from searching and switching the PLMN again, thereby improving the network recovery speed of the terminal device.

In some embodiments, the method further includes: after registering the third network fails, registering a fourth network of the third network standard of the second VPLMN.

Through the method provided in this embodiment, when the terminal device cannot search for an RPLMN network with a lower network standard (such as 3G), it can search for a network with that network standard (such as 3G) in other VPLMNs, thereby ensuring that the terminal device network does not fall back to a lower standard (such as 2G).

In some embodiments, registering the second network of the second network standard of the second VPLMN includes: obtaining frequency information of the second network; searching for a target cell meeting a registration condition in the second network based on the frequency information; and registering the target cell.

Exemplarily, the frequency information is historical frequency information of the second network stored locally; or, the frequency information is historical frequency information of the second network obtained from a server, and the historical frequency information is uploaded by the terminal device and/or other terminal devices.

Through the method provided in this embodiment, the terminal device can avoid searching for the target cell in the full frequency band on the second network as much as possible, thereby improving the cell search rate and the network recovery speed of the terminal device.

In a second aspect, an embodiment of the present application further provides a network selection device, which is applied to a terminal device, wherein a SIM card of the terminal device supports a first VPLMN and a second VPLMN, and the device specifically includes:

The network registration module is configured to register a first network of a first network standard of a first VPLMN.

The network detection module is used to detect whether the first network can provide services to the terminal device after the first network is successfully registered.

The network registration module is further configured to register the terminal device with the second network after the first network fails to provide services to the terminal device and a second network of a second network standard of a second VPLMN is searched for, wherein the first network standard is the same as the second network standard, or the second network standard is higher than the first network standard.

In a third aspect, an embodiment of the present application provides a terminal device, which includes a memory, a processor, and a computer program stored in the memory and runnable on the processor, and when the processor executes the computer program, it implements the network selection method shown in the first aspect above.

In a fourth aspect, an embodiment of the present application provides a computer-readable storage medium, which stores a computer program. When the computer program is executed by a processor, it implements the network selection method shown in the first aspect above.

In a fifth aspect, an embodiment of the present application provides a chip, which includes a processor and a memory, wherein a computer program is stored in the memory, and when the computer program is executed by the processor, the network selection method shown in the first aspect above is implemented.

In a sixth aspect, an embodiment of the present application provides a computer program product, which includes a computer program. When the computer program is executed by an electronic device, the electronic device implements the network selection method shown in the first aspect.

It can be understood that the beneficial effects of the second to sixth aspects mentioned above can be found in the relevant description of the first aspect mentioned above, and will not be repeated here.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG1 is a schematic diagram of the structure of a communication system provided in an embodiment of the present application;

FIG2 is a schematic flow chart of a network selection method provided in one embodiment of the present application;

FIG3 is a schematic diagram of a network selection scenario provided in an embodiment of the present application;

FIG4 is a schematic flow chart of a network selection method provided in another embodiment of the present application;

FIG5 is a schematic structural diagram of a network selection device 500 provided in one embodiment of the present application;

FIG6 is a schematic diagram of the structure of the chip provided in an embodiment of the present application.

DETAILED DESCRIPTION

The technical solutions provided in the embodiments of the present application are described below with reference to the accompanying drawings.

It should be understood that in the description of the embodiments of the present application, unless otherwise specified, "/" means or, for example, A/B can mean A or B; "and/or" in this article is merely a way to describe the association relationship of associated objects, indicating that three relationships can exist, for example, A and/or B can mean: A exists alone, A and B exist at the same time, and B exists alone.

In this embodiment, the terms "first" and "second" are used for descriptive purposes only and should not be understood to indicate or imply relative importance or implicitly specify the number of the technical features indicated. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of this embodiment, unless otherwise specified, "plurality" means two or more.

To facilitate description and understanding, the basic concepts involved in the embodiments of the present application are first explained.

(1)PLMN

A public land mobile network (PLMN) is a network used by operators to provide land mobile communication services to the public. Each operator has one or more PLMNs.

PLMNs are identified by their mobile country code (MCC) and mobile network code (MNC). For ease of description, PLMNs can be expressed as PLMN = MCC + MNC. The MCC uniquely identifies the country to which the public land mobile network belongs. For example, China's MCC is 460, Thailand's MCC is 520, and Singapore's MCC is 525. The MNC identifies the network within the corresponding country. An operator can use one or more MNCs to identify its network. For example, China Mobile's MNCs include 00, 02, 04, and 07; China Unicom's MNCs include 01, 06, and 09; China Telecom's MNCs include 03, 05, and 11; and China Tietong's MNC includes 20. It can be understood that China Mobile's PLMNs include 46000, 46002, 46004, and 46007, while China Telecom's PLMNs include 46001, 46006, and 46009.

For a terminal device, it needs to maintain the following types of PLMNs in the form of a list. Specifically including:

RPLMN (register PLMN): The PLMN registered by the terminal device before it was last turned on or disconnected from the network, saved in the SIM card or memory of the terminal device.

EPLMN (equivalent PLMN): A PLMN that is equivalent to the terminal's currently selected PLMN and has the same priority. The EPLMN is configured on the mobile switching center (MSC) or mobility management entity (MME) in the core network and is equivalent to the HPLMN in the current network. As you can see, if the user is in their home area, the EPLMN is equal to the EHPLMN. If they are roaming, the EPLMN is not equal to the EHPLMN.

HPLMN (home PLMN): The PLMN corresponding to the International Mobile Subscriber Identification Number (IMSI) in the user's universal subscriber identification module (SIM) card. A registered user has only one HPLMN.

EHPLMN (equivalent home PLMN): A local PLMN that is equivalent to the device's currently selected PLMN. Essentially, the EHPLMN and EPLMN are like China Mobile's newly established 158 network, while the PLMN is like the existing 135-139 networks. Carriers may have different number blocks for HPLMNs, such as 46000, 46002, and 46007. 46002 is the EPLMN equivalent to 46000. Carriers will write the EHPLMN to the SIM card when they flash it.

UPLMN (user controlled PLMN) is the PLMN selected by the terminal device when the user manually selects the network. UPLMN is stored in the SIM card.

OPLMN (operator controlled PLMN): When the operator burns the SIM card, the operator’s PLMN that has signed a roaming agreement with the operator will be written into the SIM card as OPLMN, which will serve as a suggestion for users to select a network later.

VPLMN (Visited PLMN): A PLMN that a mobile device visits. The VPLMN may have different or completely different MCC/MNC components from the IMSI in the SIM card. When a mobile device loses network coverage, a VPLMN is selected.

In other words, a VPLMN is the roaming network of a terminal device, also known as a roaming network. An operator typically subscribes to one or more VPLMNs. For example, one operator's VPLMNs include 52003, 52004, 52005, 52501, and 52502. When a mobile terminal loses coverage in its home network (i.e., when the terminal device cannot search for the HPLMN and EHPLMN subscribed to its SIM card), it selects a VPLMN from the available VPLMNs and enters roaming mode.

It should be noted that VPLMN and HPLMN usually belong to different operators. They can belong to different operators in different countries or to operators in different regions of the same country. For example, the VPLMN belongs to operator A in country A, and the HPLMN belongs to operator B in country B. Alternatively, the VPLMN belongs to operator A in country A, and the HPLMN belongs to operator C in country A.

APLMN (approve PLMN, captureable PLMN) is a PLMN on which the terminal device can find at least one cell and read its PLMN identification information.

FPLMN (Forbidden PLMN): A PLMN that is prohibited from access. Usually, when a terminal attempts to access a PLMN and is rejected, it will add it to the FPLMN list.

(2) Network standard

A network standard refers to the type of network, also known as a communication standard or standard. Currently, network standards include, but are not limited to, second-generation wireless telephone technology (2G), third-generation wireless telephone technology (3G), fourth-generation wireless telephone technology (4G), and fifth-generation wireless telephone technology (5G), as well as other future communication technologies (such as sixth-generation wireless telephone technology (6G)).

It's important to note that network generations (i.e., 2G, 3G, 4G, 5G, and 6G) are named based on the network's development history. Each generation of communication networks typically includes one or more types, depending on the communication protocols used. For example, 2G networks include Global System of Mobile Communications (GSM) and Code Division Multiple Access (CDMA). 3G networks include Wideband Code Division Multiple Access (WCDMA), Time Division-Synchronous CDMA (TD-SCDMA), and Universal Mobile Telecommunications System (UMTS). 4G networks include Long Term Evolution (LTE). 5G networks include New Radio (NR).

Generally speaking, the higher the network standard, the faster the network transmission rate, and the better the communication quality. For example, the communication quality of 5G network is better than that of 4G network, the communication quality of 4G network is better than that of 3G network, and the communication quality of 3G network is better than that of 2G network.

In this embodiment, high network standards (referred to as high standards) and low network standards (referred to as low standards) are relative concepts. For example, the network standards decrease in order of 6G, 5G, 4G, 3G, and 2G. Specifically, for 5G and 4G, 5G is the high standard, while 4G is the low standard. For 4G and 3G, 4G is the high standard, while 3G is the low standard. For 3G and 2G, 3G is the high standard, while 2G is the low standard.

(3) Roaming

Roaming refers to the ability of a mobile communications system to continue providing service to a terminal device even after it leaves its registered service area and moves to another service area. In other words, roaming allows a terminal device to communicate using another PLMN network, leaving its own HPLMN or EHPLMN network. Roaming is typically only possible between cities within a country with compatible network standards and established connectivity, or between regions or countries with established bilateral roaming agreements.

(4) Location Area

To facilitate network equipment in determining the location of a terminal device, each PLMN's coverage area is divided into multiple location areas (LAs). Each LA can contain one or more cells. The network equipment stores the current LA of each terminal device and uses this information as location information for future paging calls to the terminal device. Furthermore, the network equipment pages the terminal device by paging all cells in the terminal device's LA. Because cells often overlap, the same location may be covered by multiple LAs.

The technical solutions of the embodiments of the present application are described in detail below with reference to the accompanying drawings.

FIG1 is a schematic diagram of the structure of a communication system provided by an embodiment of the present application. The system includes terminal equipment and network equipment. Taking a 5G communication system as an example, the network equipment includes access network equipment, core network equipment, and a data network (DN). The details are as follows.

Terminal devices connect to the operator's access network equipment via wireless air interfaces and then to the data network through core network equipment. After powering on or disconnecting from the network, the terminal device first selects a PLMN. Within the selected PLMN, it then searches for a suitable cell based on the network standards supported by the PLMN. Finally, it registers and resides in the cell based on the SIM card information. After successful registration, the terminal device can enjoy network services such as voice, data, and multimedia.

In some embodiments, the process of selecting a PLMN by a terminal device is as follows:

Terminal devices typically maintain a PLMN list, which includes PLMNs of varying priorities and the network standards supported by some PLMNs. For example, as shown in Table 1, the PLMN list, from top to bottom, includes RPLMN, EPLMN, HPLMN, EHPLMN, UPLMN, OPLMN, VPLMN, and other PLMNs. Other PLMNs refer to all PLMNs that the terminal can currently search. PLMNs are ranked in descending order of priority from top to bottom.

Table 1 PLMN list

During PLMN selection, the terminal device searches for PLMNs based on the PLMN list, in descending order of PLMN priority. After successfully finding a PLMN, it selects that PLMN as the selected PLMN for subsequent cell searches. For example, after finding the RPLMN, the terminal device then searches for a cell in the RPLMN.

In some embodiments, the process of searching for a cell by a terminal device is as follows:

The PLMN selected by the terminal device usually supports multiple network standards. For example, the selected RPLMN supports four network standards: 5G, 4G, 3G, and 2G. Normally, the terminal device searches for cells in descending order of network standards, and preferentially resides in cells with higher standards. For example, a cell search is first performed under the 5G standard. If no suitable cell is found under the 5G standard, a cell search is performed under the 4G standard. If no suitable cell is found under the 4G standard, a cell search is performed under the 3G standard. If no suitable cell is found under the 3G standard, a cell search is performed under the 2G standard.

After searching for a suitable cell, the terminal device initiates network registration to the core network and data network through the access network device according to the information of the SIM card installed therein, so as to reside in the cell through the SIM card.

In this embodiment, the terminal device includes user equipment (UE), a mobile station, a mobile terminal, and a communication device capable of installing a SIM card. For example, the terminal can be a mobile phone, a smart watch, a smart bracelet, a tablet computer, a laptop computer, a PDA, a mobile internet device (MID), a virtual reality (VR) device, an augmented reality (AR) device, a wireless terminal in industrial control, a wireless terminal in self-driving, a wireless terminal in remote medical surgery, a wireless terminal in smart grid, a wireless terminal in transportation safety, a wireless terminal in smart city, or a wireless terminal in smart home. The embodiments of this application do not limit the specific technology and specific device form adopted by the terminal.

Access network equipment is primarily used to implement wireless physical layer functions, resource scheduling and wireless resource management, wireless access control, and mobility management. In this embodiment, the access network equipment can be an access network (AN) or a radio access network (RAN) device.

In the embodiments of the present application, the access network devices include but are not limited to: evolved node B (eNB), radio network controller (RNC), node B (NB), base station controller (BSC), base transceiver station (BTS), home network equipment (e.g., home evolved Node B, or home Node B, HNB), baseband unit (BBU), access point ( The invention relates to a wireless access point (AP), a wireless relay node, a wireless backhaul node, a transmission and reception point (TRP), a transmission point (TP), etc.; it can also be a device used in 5G, 6G and other systems, such as a gNB in an NR system, or a transmission point (TRP or TP), one or a group of antenna panels (including multiple antenna panels) of a network device in a 5G system, or it can also be a network node constituting a gNB or a transmission point, such as a baseband unit (BBU), a distributed unit (DU), or an RSU in a vehicle to everything (V2X) or smart driving scenario.

In some deployments, a gNB may consist of a centralized unit (CU) and a DU. The gNB may also include a radio unit (RU). The CU implements some gNB functions, while the DU implements some gNB functions. For example, the CU implements radio resource control (RRC) and packet data convergence protocol (PDCP) layer functions, while the DU implements radio link control (RLC), media access control (MAC), and physical (PHY) layer functions. Because RRC layer information ultimately becomes PHY layer information, or is converted from PHY layer information, in this architecture, higher-layer signaling, such as RRC layer signaling, can be considered to be sent by the DU, or by both the DU and the CU. It is understood that a network device can be a CU node, a DU node, or a device that includes both a CU and a DU node. In addition, CU can be divided into network equipment in the access network (radio access network, RAN), and CU can also be divided into network equipment in the core network (core network, CN), which is not limited in this application.

The core network equipment includes functional units such as the access and mobility management function (AMF), session management function (SMF), policy control function (PCF), and operation, administration and maintenance (OAM). These functional units can work independently or be combined to implement certain control functions. For example, AMF, SMF, and PCF can work together to complete access control and mobility management functions such as access authentication, security encryption, and location registration for terminal devices, as well as session management functions such as the establishment, release, and modification of user plane transmission paths, and the analysis of some network slice-related data and terminal device-related data. In this embodiment, the core network equipment only needs to be able to implement the above-mentioned network element functions. This embodiment does not limit the specific network element deployment method in the core network equipment.

The data network can correspond to a variety of different business domains, such as IP multimedia subsystem (IMS), the Internet, and third-party application-related business areas. It is mainly used to provide a variety of data business services for terminal devices, which may include servers (such as third-party application servers), routers, gateways and other devices.

It should be noted that Figure 1 is only a schematic architecture diagram of the 5G communication system. In addition to the functional units shown in Figure 1, the network architecture of the communication system may also include other functional units or functional entities, which is not limited in this embodiment.

Currently, in roaming scenarios, terminal devices can usually only search for VPLMN. According to the network search rules of the terminal device, the terminal device will give priority to registering the high-standard network of the VPLMN, and after successful registration, the VPLMN will be marked as RPLMN and stored in the PLMN list. In the subsequent process, if the terminal device detects that the high-standard network of the RPLMN is temporarily unavailable, it will automatically fall back to the low-standard network of the RPLMN. It is understandable that due to the change from high to low network standard, the terminal device cannot use the high-speed and high-quality voice call services provided by the high standard, such as voice over long-term evolution (VoLTE) and voice over New Radio (VoNR), etc., resulting in poor communication quality of the terminal device, which seriously affects the user experience.

In one example, if a terminal device is roaming and successfully registers on VPLMN1 5G, VPLMN1 is stored as the terminal device's RPLMN in the PLMN list. Later, if the terminal device detects that it has lost access to the tracking area (TA) of the current network and still cannot find a suitable cell in the current cell, it will prioritize registering on a lower-standard RPLMN network, such as the RPLMN 4G network, when reselecting a network. In this case, the terminal device's network standard drops from 5G to 4G, resulting in poor communication quality.

To this end, an embodiment of the present application provides a network selection method for improving the communication quality of a terminal device after it is disconnected from the network and reselects a network in a roaming scenario.

Figure 2 is a schematic flowchart of a network selection method provided by an embodiment of the present application. This method involves the process of selecting a network after a terminal device is disconnected from the network in a roaming scenario. The SIM card installed in the terminal device supports a first VPLMN and a second VPLMN. The first VPLMN and the second VPLMN are different, and the second VPLMN is any VPLMN supported by the SIM card other than the first VPLMN. The method specifically includes the following steps S201 to S203.

S201: A terminal device successfully registers with a first network of a first network standard of a first VPLMN.

In one example, the first network is a VPLMN14G network. It should be noted that after the terminal device successfully registers the VPLMN14G network, the VPLMN1 will be stored in the PLMN list as an RPLMN by the terminal device.

In addition, the coverage of the first network generally includes multiple location areas, such as the first location area and the second location area. Based on this, the terminal device successfully registers with the first network of the first network standard of the first VPLMN, specifically, the terminal device successfully registers with the first cell of the first location area.

S202: The terminal device detects that the first network cannot provide services to the terminal device.

In some embodiments, during the registration update process, if the terminal device cannot search for a cell that meets the registration conditions under the first network, it is determined that the first network cannot provide services to the terminal device.

Specifically, after the terminal device is connected to the network, in order for the network device to know the specific location of the terminal device, the terminal device needs to perform registration updates, including periodic registration updates and mobile registration updates. Among them, when the terminal device is in the connection management idle (connect management-Idle, CM-Idle) state and the terminal device's timer expires, the terminal device performs the periodic registration update process. In addition, the terminal device may move a long distance during the mobile process. When the TA where the terminal device is located does not match the TA supported by the terminal device (that is, the TA issued by the AMF), the terminal device will initiate the mobile registration update process.

Due to reasons such as the movement of the terminal device or changes in the service quality of the first network, the terminal device may leave the coverage area of the first network, be located at the edge of the first network's coverage area, or experience an anomaly in the first network. In these situations, the terminal device may not be able to search for a cell that meets the registration requirements during registration update, resulting in the terminal device being unable to connect to the first network, i.e., being disconnected from the network. Therefore, if the terminal device cannot search for a cell that meets the registration requirements under the first network during registration update, it is determined that the first network cannot provide service to the terminal device.

In other embodiments, during the registration update process, the terminal device can search for cells that meet the registration requirements under the first network, but during the registration process, it is found that these cells are unavailable due to network congestion, access prohibition, link establishment failure, etc., resulting in the registration update failure of the terminal device. In this case, the terminal device also believes that the first network cannot provide services to the terminal device.

In some other embodiments, after receiving the first indication information sent by the network device, the terminal device confirms that the first network cannot provide services to the terminal device. The first indication information is used to indicate that the terminal device cannot temporarily use the first network.

Specifically, because the terminal device is in a roaming location, and due to factors such as the user capacity, current number of users, and usage policies of the roaming location's first network, the network equipment in the roaming location may temporarily prohibit the roaming terminal device from using the first network during the terminal device's registration update process. For example, when the number of users on the first network exceeds a threshold, to ensure communication quality for users in the home location, the network equipment in the roaming location may temporarily prohibit the roaming device from using the first network and send a first indication message to the terminal device, indicating that the terminal device is temporarily unable to use the first network. Therefore, after receiving the first indication message sent by the network equipment, the terminal device confirms that the first network cannot provide services to the terminal device.

S203: If the terminal device searches for a second network of a second network standard of a second VPLMN, register with the second network.

In this embodiment, the first network standard is the same as the second network standard, or the second network standard is higher than the first network standard. For example, the first network is a VPLMN 14G network, and the second network is a VPLMN 24G network, or the second network is a VPLMN 25G network, or the second network is a VPLMN 34G network.

In some embodiments, the terminal device supports a self-learning network selection function. For example, as shown in Table 2, the terminal device supports recording VPLMNs that it has successfully registered in different roaming locations and frequency information of each VPLMN.

Table 2

In other embodiments, the server of the terminal device supports a self-learning network selection function. Specifically, after successfully registering at a roaming location, each terminal device connected to the server will send the corresponding roaming location information, historical VPLMN, and historical frequency information to the server. The server processes the information sent by each terminal device, generates a correspondence between the roaming location, historical VPLMN, and historical frequency information, such as shown in Table 2, and stores the correspondence on the server.

Based on this, when searching for a second network, the terminal device can first obtain the historical VPLMNs corresponding to the current roaming location and the historical frequency information of each VPLMN from a local server or a server. Subsequently, the terminal device searches for a second network based on historical VPLMNs other than the first VPLMN. After finding the historical VPLMN, the terminal device performs a cell search based on the historical frequency information to increase the likelihood of a successful network search. For example, if a terminal device is roaming in Thailand and disconnects from RPLMN 52003, it will prioritize searching for network 52004, where it was previously successfully registered, and will prioritize searching for a cell based on historical frequency information f3.

It should be noted that if the terminal device fails to search for the historical VPLMN corresponding to the current roaming location, it attempts to search for cells in all currently searchable VPLMNs and register. Alternatively, if the terminal device searches for a historical VPLMN (such as 52004), but fails to find a cell that meets the second network standard and registration conditions based on the historical frequency information of the VPLMN (such as f3), it performs a cell search within the frequency band of the second network standard of the 52004 network.

It should be understood that the terminal device may or may not be able to search for the second network. If the second network is not found, it will fall back to a network with a lower standard than the RPLMN, for example, from the RPLMN 4G network to the RPLMN 3G network. If the second network is found, it will register with the second network.

For steps S201-S203 above, let's assume that the terminal device's HPLMN is 46000, its EHPLMNs include 46002, 46004, and 46007, and its SIM card's corresponding operator's VPLMNs include 52003, 52004, and 52005. The terminal device successfully registers with VPLMN 520034G and marks it as RPLMN 520034G. Later, if the terminal device detects that RPLMN 520034G is unavailable, it can re-register with another VPLMN.

In some embodiments, as shown in Figure 3, a terminal device searches for the VPLMN 520054G network. The terminal device then registers with the network. If registration is successful, the terminal device switches from the RPLMN 520034G network to the VPLMN 520054G network. This shows that while the PLMN used by the terminal device has changed, the network standard remains unchanged, ensuring the quality of the terminal device.

In other embodiments, the terminal device searches for the VPLMN 520055G network. Subsequently, the terminal device registers with the network. If registration is successful, the terminal device switches from the RPLMN 520034G network to the VPLMN 520055G network. This indicates that not only has the PLMN used by the terminal device changed, but the network standard has also been upgraded, which helps improve the terminal device's communication quality.

Optionally, before searching for the second network of the second network standard of the second VPLMN, the terminal device may also search other location areas (such as the second location area) covered by the first network to see whether there is a second cell that meets the registration conditions.

If there is no second cell meeting the registration conditions in other location areas of the first network, the terminal device searches for the second network again.

If a second cell meeting the registration requirements exists in another location area of the first network, the terminal device registers with the second cell. If registration with the second cell succeeds, the terminal device remains on the first network, avoiding PLMN handover. If registration with the second cell fails, the terminal device searches for the second network.

In addition, during the process of registering the second network, the terminal device may successfully register and reside on the network. However, the terminal device may fail to register the second network due to reasons such as illegal users, illegal terminals, PLMN not allowed, 5G services not allowed, TA not allowed, roaming not allowed in this TA, no suitable cells in the current TA, network congestion, unauthorized network services, the network not accepting mobility and periodic registrations, and the network being unable to derive the terminal device identity.

If the terminal device fails to register with the second network, it can search for a third network of the RPLMN, which is a lower standard than the first network. For example, after searching for the RPLMN 3G network, the terminal device can register with it. After successfully registering with the third network, the terminal device can reside on the third network.

If the terminal device fails to register with the third network, it can continue searching for a third network standard of another VPLMN, i.e., a fourth network, and register with it after finding it. For example, after searching for the second VPLMN 3G network, the terminal device can register with it. After successfully registering with the third network, the terminal device can reside on that third network.

To sum up, through the network selection method provided in the embodiment of the present application, after the terminal device is disconnected from the network in a roaming scenario, it can preferentially connect to the high-standard network of other VPLMNs, and avoid the terminal device's network from dropping from a high standard to a low standard as much as possible, thereby ensuring the communication quality of the terminal device and improving the user experience.

The network selection method provided in the embodiment of the present application is further described below with reference to specific examples.

Figure 4 is a schematic flow chart of a network selection method provided in another embodiment of the present application. The method specifically includes the following steps.

S401: The terminal device successfully registers the first cell of the VPLMN1 4G network in the first location area and identifies the network as the RPLMN 4G network. For example, after the terminal device is powered on or network coverage is restored in Thailand, it successfully registers the 52003 4G network in cell 1 of location area 1 and identifies the currently used 52003 as the RPLMN.

S402: When the terminal device is updating its registration on the RPLMN 4G network, it detects that the network is temporarily unable to provide services to the terminal device.

In some embodiments, after detecting that the RPLMN 4G network cannot provide services to the terminal device, the terminal device can attempt to perform network registration through the processes shown in the following parts (1) to (6) to restore the device network.

(1) The terminal device attempts to register the second cell of the RPLMN 4G second location area.

At step S403a, the terminal device determines whether a second cell in the second location area exists on the RPLMN 4G network and can be registered. If so, the terminal device proceeds to step S403b. If not, the terminal device proceeds to step S404a.

S403b, the terminal device registers in the second cell of the second location area of the RPLMN 4G network.

At step S403c, the terminal device determines whether registration with the second cell in the second location area of the RPLMN 4G network is successful. If registration is successful, the terminal device resides in the second cell, and the network registration process ends. If registration fails, the terminal device jumps to step S403a to continue the network search.

(2) The terminal device attempts to register with other VPLMN 4G/5G networks.

In step S404a, the terminal device determines whether a 4G/5G network of another VPLMN is found. If a 4G/5G network of another VPLMN is found, the terminal device jumps to step S404b. If no 4G/5G network of another VPLMN is found, the terminal device jumps to step S405a.

In this embodiment, other VPLMNs refer to VPLMNs supported by the SIM card of the terminal device, excluding the VPLMN used by the terminal device before the network disconnection. For example, if the VPLMNs supported by the SIM card of the terminal device include 52003, 52004, and 52005, and the VPLMN used by the terminal device before the network disconnection is 52003, then other VPLMNs include 52004 and 52005.

S404b, the terminal device registers other VPLMN 4G/5G networks.

S404c: The terminal device determines whether registration with the other VPLMN 4G/5G network is successful. If so, the registration process ends. If not, the process jumps to S404a to continue the network search.

(3) The terminal device attempts to register with the RPLMN 3G network.

In step S405a, the terminal device determines whether the RPLMN 3G network is detected. If the RPLMN 3G network is detected, the process proceeds to step S405b. If the RPLMN 3G network is not detected, the process proceeds to step S406a.

S405b, the terminal device registers the RPLMN 3G network.

S405c: The terminal device determines whether it has successfully registered with the RPLMN 3G network. If so, the registration process ends. If not, the process proceeds to S405a to continue searching the network.

(4) The terminal device attempts to register with other VPLMN 3G networks.

In step S406a, the terminal device determines whether other VPLMN 3G networks are detected. If other VPLMN 3G networks are detected, the process jumps to step S406b. If no other VPLMN 3G networks are detected, the process jumps to step S407a.

S406b, the terminal device registers other VPLMN 3G networks.

S406c: The terminal device determines whether it has successfully registered with the other VPLMN 3G network. If so, the registration process ends. If not, the process jumps to S406a to continue the network search.

(5) The terminal device attempts to register with the RPLMN 2G network.

In step S407a, the terminal device determines whether the RPLMN 2G network is detected. If the RPLMN 2G network is detected, the process jumps to step S407b. If the RPLMN 2G network is not detected, the process jumps to step S408a.

S407b, the terminal device registers the RPLMN 2G network.

S407c: The terminal device determines whether it has successfully registered with the RPLMN 2G network. If so, the registration process ends. If not, the process proceeds to S407a to continue searching the network.

(6) The terminal device attempts to register with other VPLMN 2G networks.

In step S408a, the terminal device determines whether it has scanned other VPLMN 2G networks. If so, the process jumps to step S406b. If no other VPLMN 3G networks are scanned, the registration process ends.

S408b, the terminal device registers other VPLMN 2G network.

S408c, the terminal device determines whether it has successfully registered with other VPLMN 2G networks.

Since the 2G network is the lowest network standard among the currently commonly used network standards, the network registration process will end regardless of whether the terminal device successfully registers other VPLMN 2G networks.

Furthermore, since both 4G and 5G currently offer relatively good communication quality, and PLMN searches and handoffs can be time-consuming, after disconnecting from the RPLMN 5G network, a terminal device can prioritize registering on the RPLMN 4G network. If the RPLMN 4G network is unsuccessful, it can search for other VPLMN 5G/4G networks to ensure the terminal device remains on the RPLMN, avoiding PLMN handoffs and improving network recovery speed.

Based on the same concept, as an implementation of the above method, an embodiment of the present application provides a network selection device, which corresponds to the above method embodiment. For ease of reading, this device embodiment will no longer repeat the details of the above method embodiment one by one, but it should be clear that the device in this embodiment can correspond to and implement all the contents of the above method embodiment.

5 is a schematic diagram of a network selection device 500 according to an embodiment of the present application. The network selection device 500 is applied to a terminal device whose SIM card supports a first VPLMN and a second VPLMN. The device 500 includes a network registration module 501 and a network detection module 502 .

The network registration module 501 is configured to register a first network of a first network standard of a first VPLMN, for example, registering a first cell in the first location area when the coverage area of the first network includes a first location area and a second location area that are different but partially overlap.

The network detection module 502 is configured to detect whether the first network can provide services to the terminal device after the first network registration is successful.

The network registration module 501 is further configured to register the terminal device with the second network after the first network fails to provide services to the terminal device and a second network of a second network standard for registering a second VPLMN is found, wherein the first network standard is the same as the second network standard, or the second network standard is higher than the first network standard.

Optionally, the network registration module 501 is also used to register a second network of the second network standard of the second VPLMN if a second cell meeting the registration conditions is not searched in the second location area of the first network; or, if a second cell meeting the registration conditions is searched in the second location area of the first network but registration of the second cell fails, register the second network.

Optionally, the network registration module 501 is further configured to mark the first VPLMN as a registered public land mobile network RPLMN; and, after the second network registration fails, register a third network of a third network standard of the RPLMN; the third network standard is lower than the first network standard.

Optionally, the network registration module 501 is further configured to, after registration of the third network fails, register a fourth network of the third network standard of the second VPLMN.

Optionally, the network registration module 501 is further configured to, during registration of the second network, obtain frequency information of the second network; search for a target cell in the second network that meets registration conditions based on the frequency information; and register the target cell.

An embodiment of the present application also provides a terminal device, which includes a memory, a processor, and a computer program stored in the memory and executable on the processor. When the processor executes the computer program, the network selection method shown in the above embodiments is implemented.

An embodiment of the present application further provides a chip, as shown in FIG6 , which includes a processor and a memory. The memory stores a computer program, which, when executed by the processor, implements the network selection method in the above embodiments.

An embodiment of the present application further provides a computer-readable storage medium, which stores a computer program. When the computer program is executed by a processor, the network selection method provided in the above embodiments is implemented.

An embodiment of the present application further provides a computer program product, which includes a computer program. When the computer program is executed by an electronic device, the electronic device implements the network selection method provided in the above embodiments.

It should be understood that the size of the serial numbers of the steps in the above 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.

It should be understood that the processor mentioned in the embodiments of the present application may be a central processing unit (CPU), or other general-purpose processors, digital signal processors (DSP), application-specific integrated circuits (ASIC), field programmable gate arrays (FPGA), 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.

It should also be understood that the memory mentioned in the embodiments of the present application may be a volatile memory or a non-volatile memory, or may include both volatile and non-volatile memories. Among them, the non-volatile memory may be a read-only memory (ROM), a programmable read-only memory (PROM), an erasable programmable read-only memory (EPROM), an electrically erasable programmable read-only memory (EEPROM), or a flash memory. The volatile memory may be a random access memory (RAM), which is used as an external cache. By way of example and not limitation, many forms of RAM are available, such as static RAM (SRAM), dynamic RAM (DRAM), synchronous DRAM (SDRAM), double data rate synchronous dynamic random access memory (DDRSDRAM), enhanced synchronous dynamic random access memory (ESDRAM), synchronous link dynamic random access memory (SLDRAM), and direct rambus RAM (DRRAM).

In the embodiments provided in this application, the division of each framework or module is merely a logical function division. In actual implementation, there may be other division methods, for example, multiple frameworks or modules can be combined or integrated into another system, or some features can be ignored or not executed.

In addition, the functional modules in the various embodiments of the present application may be integrated into a processing module, or each module may exist physically separately, or two or more modules may be integrated into a single module. The above-mentioned integrated modules may be implemented in the form of hardware or software functional modules.

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

References to "one embodiment" or "some embodiments" in this specification mean that a particular feature, structure, or characteristic described in conjunction with that embodiment is included in one or more embodiments of the present application. Thus, phrases such as "in one embodiment," "in some embodiments," "in other embodiments," and "in other embodiments" appearing in various places in this specification do not necessarily refer to the same embodiment, but rather mean "one or more but not all embodiments," unless otherwise specifically emphasized. The terms "including," "comprising," "having," and variations thereof all mean "including but not limited to," unless otherwise specifically emphasized.

The above-described embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. These modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the various embodiments of the present application, and should all be included in the scope of protection of the present application.

Claims (11)

A network selection method, characterized in that it is applied to a terminal device, wherein the terminal is equipped with a subscriber identity module (SIM) card, and the SIM card supports a first VPLMN and a second VPLMN, and the method comprises: Successfully registering with the first network of the first network standard of the first VPLMN; detecting that the first network cannot provide services to the terminal device, searching for a second network of a second network standard of the second VPLMN; wherein the first network standard is the same as the second network standard, or the second network standard is higher than the first network standard; After searching for the second network, register with the second network. The method according to claim 1, wherein detecting that the first network is unable to provide services to the terminal device comprises: In the first network, no cell meeting the registration conditions can be found; or, A first indication information is received, where the first indication information is used to indicate that the terminal device cannot temporarily use the first network. The method according to claim 1 or 2, characterized in that the coverage area of the first network includes different and partially overlapping first location areas and second location areas; accordingly, the first network of the first network standard of the successful registration of the first VPLMN includes: The first cell of the first location area is successfully registered. The method according to claim 3, wherein after searching for the second network of the second network standard of the second VPLMN, registering the second network comprises: If no second cell meeting the registration condition is found in the second location area, searching for a second network of the second network standard of the second VPLMN; and after finding the second network, registering with the second network; or If a second cell meeting the registration condition is searched in the second location area and registration of the second cell fails, searching for a second network of the second network standard of the second VPLMN; and registering the second network after searching for the second network. The method according to any one of claims 1 to 4, characterized in that after successfully registering the first network of the first network standard of the first VPLMN, the method further comprises: marking the first VPLMN as a registered public land mobile network RPLMN; and After failing to register the second network, register a third network of a third network standard of the RPLMN; wherein the third network standard is lower than the first network standard. The method according to claim 5, further comprising: After registering the third network fails, registering a fourth network of the third network standard of the second VPLMN. The method according to any one of claims 1 to 6, wherein the registering the second network of the second network standard of the second VPLMN comprises: Obtaining frequency information of the second network; searching, according to the frequency information, for a target cell in the second network that meets a registration condition; Register the target cell. The method according to claim 7, characterized in that The frequency information is the historical frequency information of the second network stored locally; The frequency information is historical frequency information of the second network obtained from a server, and the historical frequency information is uploaded by the terminal device and/or other terminal devices. A terminal device, characterized in that it includes a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor implements the method according to any one of claims 1 to 8 when executing the computer program. A computer-readable storage medium, characterized in that the computer-readable storage medium stores a computer program, and when the computer program is executed by a processor, it implements the method according to any one of claims 1 to 8. A chip, characterized in that the chip comprises a processor and a memory, wherein a computer program is stored in the memory, and when the computer program is executed by the processor, the method according to any one of claims 1 to 8 is implemented.