WO2018153274A1

WO2018153274A1 - Call setup method and terminal device

Info

Publication number: WO2018153274A1
Application number: PCT/CN2018/075796
Authority: WO
Inventors: 袁锴; 段小嫣; 张博; 睢菲菲; 丁明
Original assignee: 华为技术有限公司
Priority date: 2017-02-27
Filing date: 2018-02-08
Publication date: 2018-08-30
Also published as: CN108696853A; CN112995972A; CN108696853B; CN112995972B

Abstract

A call setup method applicable to a terminal device and the corresponding terminal device. The method comprises: sending a first request message to a network device of a first communication network, the terminal device currently residing in a cell of the first communication network, the first request message comprising an emergency call indication information; receiving a first response message sent by the network device, the first response message comprising the carrier frequency parameter of a second communication network; measuring first cells, the first cells comprising at least one cell of the second communication network, both the carrier frequency and carrier frequency parameter of each cell of the first cells satisfying preset relations; determining whether a second cell supports an emergency call service, the second cell being one cell of the first cells; when the second cell supports the emergency call service, residing in the second cell; sending a second request message to the network device of the second communication network, the second request message being used for requesting the setup of an emergency call.

Description

Call establishment method and terminal device

Technical field

The embodiments of the present invention relate to the field of communications technologies, and in particular, to a call setup method and a terminal device.

Background technique

The Long Term Evolution (LTE) system belongs to the fourth generation mobile communication system (English: 4th Generation, 4G for short). The LTE network usually supports faster data rates than 2G and 3G networks. However, in some cases, the LTE network may not fully support some services that can be processed by the legacy network, so the deployment of the LTE network and the legacy network usually has overlapping areas, and when the service needs, the terminal equipment can be in the LTE network and the traditional network. Convert between. For example, in some cases, the LTE network does not support voice calls, so when the terminal device receives or initiates a voice call while connecting to a network that supports the data session but does not support the voice call, the terminal device can perform circuit switching fallback. : Circuit Switched Fallback (CSFB) process to fall back to the traditional network that supports voice calls.

When the terminal device returns to a traditional network, such as a Global System for Mobile Communications (GSM) network, and initiates an emergency call (for example, dialing an emergency call number such as 110 or 911) by performing a CSFB process, Sometimes an emergency call fails.

Summary of the invention

The embodiment of the invention provides a method for establishing a call to improve the success rate of establishing an emergency call after the terminal device CSFB.

In a first aspect, an embodiment of the present invention provides a method for establishing a call, where the method is applied to a terminal device, including:

Sending a first request message to a network device in the first communication network, where the terminal device currently resides in a cell in the first communication network, the first request message includes emergency call indication information, and receives a first response message sent by the network device, The first response message includes a carrier frequency parameter in the second communication network; performing measurement on the first cell, where the first cell includes at least one cell in the second communication network, and a carrier frequency of each cell in the first cell The carrier frequency parameter satisfies the preset relationship; determining whether the second cell supports the emergency call service, where the second cell is a cell in the first cell; when the second cell supports the emergency call service, camping on the second cell; The network device in the second communication network sends a second request message, wherein the second request message is used to request to establish an emergency call.

With reference to the first aspect, in an implementation manner, the method further includes: determining, when the second cell does not support the emergency call service, whether the third cell supports the emergency call service, where the third cell is the second cell except the second cell A cell other than that.

In combination with the first aspect and all of its implementations, in another implementation, the carrier frequency parameter includes a carrier frequency, a plurality of carrier frequencies, or a carrier frequency range. When the carrier frequency parameter includes a carrier frequency, the preset relationship includes the cell frequency and a carrier frequency being the same; when the carrier frequency parameter includes multiple carrier frequencies, the preset relationship includes the cell frequency being one of multiple carrier frequencies; when the carrier frequency When the parameter includes a carrier frequency range, the preset relationship includes the cell frequency within a carrier frequency range.

With reference to the first aspect and all implementations thereof, in another implementation manner, determining whether the second cell supports the emergency call service includes: when the system information broadcasted by the second cell broadcasts, the emergency call EC value is 0, or when When the emergency call EC value in the system information of the two cell broadcast is 1 and the access category of the terminal device belongs to the category 11-15, it is determined that the second cell supports the emergency call service; when the system information of the second cell broadcast is allowed When the emergency call EC value is 1, and the access category of the terminal device does not belong to the category 11-15, it is determined that the second cell does not support the emergency call service.

In combination with the first aspect and all implementations thereof, in another implementation, before camping on the second cell, the method further includes: determining an ID of the public land mobile network PLMN to which the second cell belongs, and the first PLMN ID or the second PLMN. Whether the ID is the same, when the ID of the PLMN to which the second cell belongs is the same as the first PLMN ID or the second PLMN ID, the step of camping to the second cell is triggered, where the first PLMN ID is the ID of the PLMN currently registered by the terminal device, The second PLMN ID is the ID of the PLMN equivalent to the PLMN currently registered by the terminal device.

With reference to the first aspect and all implementations thereof, in another implementation manner, the method further includes: determining, when the ID of the PLMN to which the second cell belongs, and the first PLMN ID or the second PLMN ID are different, determining whether the second cell is The cell with the strongest received signal power in the cell that meets the preset condition in the first cell, when the second cell is the cell with the strongest received signal power in the cell that meets the preset condition in the first cell, triggers the camp to the first The steps of the two cells.

With reference to the first aspect and all implementations thereof, in another implementation manner, the first communication network is a long term evolution LTE network, and the second communication network is a global mobile communication system GSM network.

In a second aspect, an embodiment of the present invention provides a method for establishing a call, where the method is applied to a terminal device, including: sending a first request message to a network device in a first communication network, where the terminal device currently resides in the first communication a cell in the network, the first request message includes emergency call indication information, and a first response message sent by the network device, where the first response message includes a carrier frequency parameter in the second communication system, and the first cell is measured, where A cell includes at least one cell in the second communication network, and a carrier frequency and a carrier frequency parameter of each cell in the first cell satisfy a preset relationship; camping on the second cell, where the second cell is in the first cell a cell that determines whether the second cell supports the emergency call service; and when the second cell does not support the emergency call service, determines whether the third cell supports the emergency call service, where the third cell is other than the second cell in the first cell. a cell; when the third cell supports the emergency call service, reselecting to the third cell; to the second communication network The network device sends a second request message, wherein the second request message for requesting establishment of an emergency call.

With reference to the second aspect, in an implementation manner, the method further includes: determining whether the second cell supports the emergency call service, including: when the system information broadcasted by the second cell, the emergency call EC value is 0, or when the second cell When the emergency call EC value in the broadcast system information is 1 and the access category of the terminal device belongs to the category 11-15, it is determined that the second cell supports the emergency call service; when the emergency call is allowed in the system information broadcasted by the second cell When the EC value is 1, and the access category of the terminal device does not belong to the category 11-15, it is determined that the second cell does not support the emergency call service.

In combination with the second aspect and all of its implementations, in another implementation, the carrier frequency parameter includes a carrier frequency, a plurality of carrier frequencies, or a carrier frequency range. When the carrier frequency parameter includes a carrier frequency, the preset relationship includes the cell frequency and a carrier frequency being the same; when the carrier frequency parameter includes multiple carrier frequencies, the preset relationship includes the cell frequency being one of multiple carrier frequencies; when the carrier frequency When the parameter includes a carrier frequency range, the preset relationship includes the cell frequency within a carrier frequency range.

With reference to the second aspect and all the implementation manners, in another implementation manner, determining whether the second cell supports the emergency call service comprises: determining, according to the saved historical information, whether the second cell supports the emergency call service, where the historical information is the terminal Whether the second cell acquired by the system information broadcasted by the second cell supports the information of the emergency call service when the device is historically camped on the second cell.

With reference to the second aspect and all implementations thereof, in another implementation, before camping on the second cell, the method further includes: determining an ID of the public land mobile network PLMN to which the second cell belongs, and the first PLMN ID or the second PLMN. Whether the ID is the same, when the ID of the PLMN to which the second cell belongs is the same as the first PLMN ID or the second PLMN ID, the step of camping to the second cell is triggered, where the first PLMN ID is the ID of the PLMN currently registered by the terminal device, The second PLMN ID is the ID of the PLMN equivalent to the PLMN currently registered by the terminal device.

With reference to the second aspect and all implementations thereof, in another implementation manner, the method further includes: determining, when the ID of the PLMN to which the second cell belongs, and the first PLMN ID or the second PLMN ID are different, determining whether the second cell is The cell with the strongest received signal power in the cell that meets the preset condition in the first cell, when the second cell is the cell with the strongest received signal power in the cell that meets the preset condition in the first cell, triggers the camp to the first The steps of the two cells.

With reference to the second aspect and all implementations thereof, in another implementation manner, the first communication network is a long term evolution LTE network, and the second communication network is a global mobile communication system GSM network.

In a third aspect, an embodiment of the present invention provides a terminal device, including: at least one transceiver, configured to: send a first request message to a network device in a first communication network, where the terminal device currently resides in the first a communication network, the first request message includes emergency call indication information; receiving a first response message sent by the network device, where the first response message includes a carrier frequency parameter in the second communication network; and transmitting the first to the network device in the second communication network a request message, wherein the second request message is used to request to establish an emergency call; the processing circuit is coupled to the at least one transceiver, and the processing circuit is configured to control the terminal device to: measure the first cell, where the first cell Include at least one cell in the second communication network, the carrier frequency and the carrier frequency parameter of each cell in the first cell satisfy a preset relationship; determine whether the second cell supports emergency call service, where the second cell is the first cell One of the cells; when the second cell supports the emergency call service, camps on the second cell.

With reference to the third aspect, in an implementation manner, the processing circuit is configured to control the terminal device to further determine, when the second cell does not support the emergency call service, whether the third cell supports the emergency call service, where the third cell is the first A cell in one cell other than the second cell.

In combination with the third aspect and all of its implementations, in another implementation, the carrier frequency parameter includes a carrier frequency, a plurality of carrier frequencies, or a carrier frequency range. When the carrier frequency parameter includes a carrier frequency, the preset relationship includes the cell frequency and a carrier frequency being the same; when the carrier frequency parameter includes multiple carrier frequencies, the preset relationship includes the cell frequency being one of multiple carrier frequencies; when the carrier frequency When the parameter includes a carrier frequency range, the preset relationship includes the cell frequency within a carrier frequency range.

With reference to the third aspect and all the implementation manners, in another implementation manner, determining whether the second cell supports the emergency call service includes: when the system information broadcasted by the second cell broadcasts, the emergency call EC value is 0, or when When the emergency call EC value in the system information of the two cell broadcast is 1 and the access category of the terminal device belongs to the category 11-15, it is determined that the second cell supports the emergency call service; when the system information of the second cell broadcast is allowed When the emergency call EC value is 1, and the access category of the terminal device does not belong to the category 11-15, it is determined that the second cell does not support the emergency call service.

With reference to the third aspect and all its implementations, in another implementation, the processing circuit is configured to control the terminal device to further determine: the ID of the public land mobile network PLMN to which the second cell belongs and the first PLMN ID or the second PLMN Whether the ID is the same, when the ID of the PLMN to which the second cell belongs is the same as the first PLMN ID or the second PLMN ID, the step of camping to the second cell is triggered, where the first PLMN ID is the ID of the PLMN currently registered by the terminal device, The second PLMN ID is the ID of the PLMN equivalent to the PLMN currently registered by the terminal device.

In combination with the third aspect and all of its implementations, in another implementation, the processing circuit is configured to control the terminal device to further: when the ID of the PLMN to which the second cell belongs is not related to the first PLMN ID or the second PLMN ID At the same time, it is determined whether the second cell is the cell with the strongest received signal power in the cell that meets the preset condition in the first cell, and the second cell is the cell with the strongest received signal power in the cell that meets the preset condition in the first cell. At the time, the step of camping to the second cell is triggered.

With reference to the third aspect and all implementations thereof, in another implementation manner, the first communication network is a long term evolution LTE network, and the second communication network is a global mobile communication system GSM network.

In a fourth aspect, an embodiment of the present invention provides a terminal device, including: at least one transceiver, configured to: send a first request message to a network device in a first communication network, where the terminal device currently resides in the first a communication network, the first request message includes emergency call indication information; receiving a first response message sent by the network device, where the first response message includes a carrier frequency parameter in the second communication network; and transmitting the first to the network device in the second communication network a request message, wherein the second request message is used to request to establish an emergency call; the processing circuit is coupled to the at least one transceiver, and the processing circuit is configured to control the terminal device to: measure the first cell, where the first cell Including at least one cell in the second communication network, the carrier frequency and the carrier frequency parameter of each cell in the first cell satisfy a preset relationship; camping on the second cell, where the second cell is one of the first cells a cell; determining whether the second cell supports emergency call service; when the second cell does not support emergency call service The third cell is determined whether the emergency call service support, wherein the third cell is the first cell other than a cell of a second cell; when the third cell supports emergency call service, reselects to the third cell.

With reference to the fourth aspect, in an implementation manner, determining whether the second cell supports the emergency call service includes: when the emergency cell call EC value in the system information broadcasted by the second cell is 0, or when the second cell broadcasts system information When the emergency call EC value is 1 and the access class of the terminal device belongs to the category 11-15, it is determined that the second cell supports the emergency call service; when the emergency cell call EC value in the system information broadcasted by the second cell is 1 When the access category of the terminal device does not belong to the category 11-15, it is determined that the second cell does not support the emergency call service.

In conjunction with the fourth aspect and all of its implementations, in another implementation, the carrier frequency parameter includes a carrier frequency, a plurality of carrier frequencies, or a carrier frequency range. When the carrier frequency parameter includes a carrier frequency, the preset relationship includes the cell frequency and a carrier frequency being the same; when the carrier frequency parameter includes multiple carrier frequencies, the preset relationship includes the cell frequency being one of multiple carrier frequencies; when the carrier frequency When the parameter includes a carrier frequency range, the preset relationship includes the cell frequency within a carrier frequency range.

With reference to the fourth aspect and all the implementation manners, in another implementation manner, determining whether the second cell supports the emergency call service comprises: determining, according to the saved historical information, whether the second cell supports the emergency call service, where the historical information is the terminal Whether the second cell acquired by the system information broadcasted by the second cell supports the information of the emergency call service when the device is historically camped on the second cell.

With reference to the fourth aspect and all its implementations, in another implementation, the processing circuit is configured to control the terminal device to further determine: the ID of the public land mobile network PLMN to which the second cell belongs and the first PLMN ID or the second PLMN Whether the ID is the same, when the ID of the PLMN to which the second cell belongs is the same as the first PLMN ID or the second PLMN ID, the step of camping to the second cell is triggered, where the first PLMN ID is the ID of the PLMN currently registered by the terminal device, The second PLMN ID is the ID of the PLMN equivalent to the PLMN currently registered by the terminal device.

With reference to the fourth aspect and all its implementations, in another implementation, the processing circuit is configured to control the terminal device to further: when the ID of the PLMN to which the second cell belongs is not related to the first PLMN ID or the second PLMN ID At the same time, it is determined whether the second cell is the cell with the strongest received signal power in the cell that meets the preset condition in the first cell, and the second cell is the cell with the strongest received signal power in the cell that meets the preset condition in the first cell. At the time, the step of camping to the second cell is triggered.

With reference to the fourth aspect and all implementations thereof, in another implementation manner, the first communication network is a long term evolution LTE network, and the second communication network is a global mobile communication system GSM network.

In the embodiment of the present invention, the terminal device determines a cell supporting the emergency call service before determining the camped cell, and then determines the camped cell in the cell supporting the emergency call service, and avoids camping on the cell of the legacy network because of the resident The cell does not support the call setup failure caused by the emergency call service, and improves the success rate of establishing an emergency call in the terminal device CSFB.

DRAWINGS

In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings to be used in the embodiments of the present invention will be briefly described below.

FIG. 1 is a schematic diagram of network overlay coverage according to an embodiment of the present invention;

2 is a structural diagram of a device of a terminal device according to an embodiment of the present invention.

FIG. 3 is a structural diagram of another apparatus of a terminal device according to an embodiment of the present invention.

4 is a flow chart of a method for establishing a call;

FIG. 5 is a flowchart of a method for establishing a call according to an embodiment of the present invention;

FIG. 6 is a flowchart of another method for establishing a call according to an embodiment of the present invention.

detailed description

The present invention will be further described in detail with reference to the accompanying drawings, in which FIG.

In the following detailed description, reference is made to the drawings in the claims Although the embodiments are described in sufficient detail to enable those skilled in the art to practice the embodiments, it should be understood that these examples are not to be construed as limiting. Modifications are made in the context of the spirit and scope of the embodiments of the invention.

FIG. 1 is a schematic diagram of network overlay coverage according to an embodiment of the present invention. FIG. 1 illustrates overlapping coverage of a 4G network 102 and a legacy network 104 in a communication system 100 based on some example embodiments. The 4G network 102 may be, for example, an LTE-based network, such as an LTE network or an LTE-A (LTE-Advanced) network, or capable of providing faster data rates than traditional networks, such as 2G and 3G networks, but does not support or Other networks that fully support voice calls. It should be understood that the 4G network is exemplified by way of example and not by way of limitation, and that the 4G network 102 in the embodiments of the present invention may provide a higher rate but may not support or insufficiently support CS voice calls, which may be future or may be developed in the future. For other networks, legacy network 104 may be any conventional network that has a CS domain to support CS voice calls. As a non-limiting example, the legacy network 104 may be a 3G network, such as Wideband Code Division Multiple Access (WCDMA), Time Division Synchronous Code Division Multiple (English: Time Division-Synchronous Code Division Multiple). Access, referred to as TD-SCDMA, Code Division Multiple Access (CDMA) 2000 network, such as 1xRTT network or other network standardized by 3GPP2 supporting CS domain. As another example, a legacy network may be a 2G network, such as a GSM network.

Both the 4G network 102 and the legacy network 104 may have coverage areas represented by corresponding circles shown in FIG. The coverage areas may overlap, such as shown by the overlapping portion of the circle in FIG. The terminal device can operate on the 4G network 102 and the legacy network 104. When the terminal device is in an overlapping coverage area, the terminal device can connect to the 4G network 102 and can perform a CSFB procedure on the legacy network 104 in response to initiating a voice call.

Hereinafter, the embodiment of the present invention will be described in detail by taking a 4G network as an LTE network and a legacy network as a GSM network.

Fig. 2 is a block diagram showing the structure of a terminal device. It should be understood that the components, devices, or components illustrated in FIG. 2 and described below with respect to FIG. 2 may not be necessary, and thus some of them may be omitted in some embodiments. Moreover, some embodiments may include other or different components, devices or elements other than those illustrated in FIG. 2 and described with respect to FIG. 2.

In some example embodiments, terminal device 200 may include processing circuitry 210 that may be configured to perform operations in accordance with one or more of the example embodiments disclosed herein. That is, the processing circuit 210 can be configured to perform and/or control the execution of one or more functions of the terminal device 200 in accordance with various exemplary embodiments, and thus can be provided for executing the terminal device 200 in accordance with various exemplary embodiments. Functional device. Processing circuitry 210 may be configured to perform data processing, application execution, and/or other processing and management services in accordance with one or more exemplary embodiments.

In some embodiments, terminal device 200, or one or more portions thereof, or one or more components, such as processing circuitry 310, can include one or more chipsets, each chipset can include one or more chips. In some cases, processing circuitry 210 and/or one or more other components of terminal device 200 may thus be configured to implement this embodiment on a single chip or chipset. In some exemplary embodiments in which one or more components of terminal device 200 are implemented as a chipset, the chipset can enable a computing device to operate in system 200 when implemented on a computing device or operatively coupled to a computing device. . For example, one or more components of terminal device 200 can provide a chipset that is configured to enable a computing device to operate on LTE network 102 and/or legacy network 104.

In some example embodiments, processing circuit 210 may include processor 212, and in some embodiments, such as the embodiment shown in FIG. 2, may also include memory 214. Processing circuit 210 can communicate with or otherwise control one or more transceivers 220.

Processor 212 can be implemented in a variety of forms. For example, processor 212 can be implemented as various processing devices, such as microprocessors, coprocessors, controllers, or various other computing or processing devices including integrated circuits such as, for example, application specific integrated circuits (ASICs), onsite Programming gate arrays (FPGAs), some combinations of them, and so on. Although illustrated as a single processor, it should be understood that processor 212 can include multiple processors. The plurality of processors can operatively communicate with one another and can be collectively configured to perform one or more functions of the terminal device 200 as described herein. In some example embodiments, processor 212 may be configured to execute instructions that may be stored in memory 214 or otherwise accessible to processor 312. Thus, whether configured by hardware or by a combination of hardware and software, processor 212 is capable of performing operations in accordance with various embodiments when configured accordingly.

In some example embodiments, memory 214 may include one or more memory devices. Memory 214 can include fixed and/or removable memory devices. In some embodiments, memory 214 can provide a non-transitory computer readable storage medium that can store computer program instructions executable by processor 212. In this regard, the memory 214 can be configured to store information, data, applications, instructions, and the like for enabling the terminal device 200 to perform various functions in accordance with one or more exemplary embodiments. In some embodiments, memory 314 can communicate with one or more of processor 212, or one or more transceivers 220, via one or more buses for communicating information between components of terminal device 200. .

The terminal device 200 may also include one or more transceivers 220. The one or more transceivers 220 can enable the terminal device 200 to transmit and receive signals to and from one or more wireless networks, such as the LTE network 102 and the legacy network 104. As such, the one or more transceivers 220 can be configured to support any type of cellular or other wireless communication technology that can be implemented by the LTE network 102 and/or the legacy network 104. In some exemplary embodiments, one or more transceivers 220 may include a single transceiver configured to enable terminal device 200 to connect to both LTE network 102 and legacy network 104. Alternatively, in some exemplary embodiments, the one or more transceivers 220 may include a first transceiver configured to enable the terminal device 200 to connect to the LTE network 102 and configured to enable the terminal device 200 to connect to the legacy A second transceiver of network 104.

Fig. 3 is a block diagram showing the structure of another terminal device. As shown in the figure, on the basis of FIG. 2, the processor 212 further includes: a GSM CM module 2120, a GSM MM module 2121, an LTE module 2122, a GSM PHY module 2123, and a GSM AS module 2124, all of which may be the processor 212. The computer program instructions are executed to implement the method flow in the embodiments of the present invention.

Figure 4 is a flow chart showing a method of call setup, including:

S401: The terminal device sends an extended service request message (Extended Service Request) to the network device in the first communication network.

The terminal device residing in the cell in the first communication network when the extended service request message is sent, the extended service request message includes a service type=mobile originating CS fallback emergency call, and the extended service request message may be used by the terminal device The LTE module transmits to the network device in the first communication network. Exemplarily, the first communication network may be an LTE network.

S402: The network device in the first communications network sends a radio resource control connection release message (RRC Connection Release) to the terminal device.

The RRC connection release message is used to indicate that the terminal device is redirected to the CS network in the second communication network, including a carrier frequency parameter (Redirected Carrier Information=geran CarrierFreqsGERAN). The carrier frequency parameter can include a carrier frequency, a plurality of carrier frequencies, or a carrier frequency range. Exemplarily, the carrier frequency parameter is a GERAN (English: GSM EDGE Radio Access Network) carrier frequency parameter, and the second communication network may be a GSM network.

S403: The LTE module of the terminal device sends a redirection instruction (ID_LRRC_GRR_REDIRECTED_REQ) to the GSM access layer (English: Access Stratum, AS for short) module of the terminal device;

The redirecting command includes a carrier frequency parameter received from the network device, the redirecting instruction being used to indicate that the GSM AS module of the terminal device is redirected to the GSM network.

S404: The GSM AS module of the terminal device sends a measurement instruction (EVT_MPH_RXLEV_REQ) to the GSM physical layer (English: Physical Layer, PHY for short) module of the terminal device;

The measurement command includes a carrier frequency parameter in the redirect command, and a preset threshold, the measurement command is used to instruct the GSM PHY module to perform measurement on the GSM cell.

S405: The GSM PHY module of the terminal device performs measurement on at least one GSM cell.

The GSM PHY module measures at least one GSM cell in which a cell carrier frequency (hereinafter referred to as a cell frequency) and a carrier frequency parameter satisfy a preset relationship. When the carrier frequency parameter includes a carrier frequency, the preset relationship includes the cell frequency and the carrier frequency being the same; when the carrier frequency parameter includes multiple carrier frequencies, the preset relationship includes the cell frequency being one of the multiple carrier frequencies; When the carrier frequency parameter includes a carrier frequency range, the preset relationship includes the cell frequency being within the carrier frequency range.

If the GSM PHY module measures the GSM cell, the GSM PHY module may be based on the pre-configured GERAN carrier frequency in the terminal device, if no GSM cell is measured on the carrier frequency in which the carrier frequency parameter in step S404 satisfies the preset relationship. The information is measured by the GSM cell, or the GSM cell is measured according to the historical GERAN carrier frequency information stored in the terminal device, to obtain the GSM cell information that meets the preset condition.

S406: The GSM PHY module of the terminal device sends the information of the GSM cell that meets the preset condition to the GSM AS module of the terminal device after the measurement;

For example, the preset condition includes: the cell received signal power is greater than or equal to a preset threshold sent by the GSM AS module to the GSM PHY module in S404.

S407: The GSM AS module of the terminal device determines a camping cell from the GSM cell that is sent by the GSM PHY module and meets the preset condition.

The GSM AS module determines the camping cell by the following method:

First, the GSM AS module sequentially determines whether the GSM cell that meets the preset condition is a suitable cell (Suitable Cell);

There may be only one or more GSM cells that meet the preset conditions. When there is only one, the GSM AS module directly determines whether the GSM cell is a suitable cell. Specifically, the GSM AS module determines the ID of the PLMN to which the GSM cell belongs and the ID of the PLMN currently registered by the terminal device according to the information sent by the GSM PHY module. Or whether the ID of the equivalent PLMN is the same, if the same, the GSM cell is determined to be a suitable cell, and the GSM cell is used as a camping cell; if not, the GSM cell is determined to be an acceptable cell. The equivalent PLMN and the PLMN currently registered by the terminal device belong to the same operator.

When there are multiple GSM cells that meet the preset conditions, the GSM AS module determines one by one according to the above method, and then selects any one of the determined suitable cells or selects the cell with the strongest received signal power as the camping cell.

Second, when there is no suitable cell in the GSM cell that meets the preset condition, the GSM AS module selects any one of the acceptable cells or selects the cell with the strongest received signal power as the camping cell.

The reason why the suitable cell is preferentially selected as the camping cell is because the terminal device can only make an emergency call in the acceptable cell, and cannot perform other services after the emergency call.

S408: The GSM AS module of the terminal device sends a cell resident instruction (ID_MPH_CAMP_SCELL_REQ) to the GSM PHY module to instruct the GSM PHY module to control the terminal device to camp on the selected cell;

S409: The GSM PHY module sends a cell camp confirmation (ID_MPH_CAMP_SCELL_CNF) to the GSM AS module.

S410: The GSM AS module sends a redirect acknowledgment (ID_LRRC_GRR_REDIRECTED_CNF) to the LTE module.

S411: The GSM AS module sends a cell information indication (GRRMM_SYS_INFO_IND) to the GSM mobility management (English: Mobility Management, MM for short) module of the terminal device;

The cell information indication includes information of the camped cell, and the information of the camped cell includes the Access-Restriction-Emergency-Service.

S412: The GSM connection management (English: Connection Management, CM for short) module of the terminal device sends a connection management service request instruction (ID_NAS_CM_SERV_REQUEST) to the GSM MM module;

The connection management service request command includes an emergency-call-establishment for requesting establishment of an emergency call.

S413: The GSM MM module sends a radio resource connection establishment request instruction (RRMM_EST_REQ) to the GSM AS module.

The radio resource connection setup request command includes an emergency-call-establishment for requesting establishment of an emergency call.

S414: The GSM AS module sends a radio resource connection establishment confirmation (RRMM_EST_CNF) to the GSM MM module.

The RRC connection establishment acknowledgment includes the establishment of a result of the access control (result=access barred) information, indicating that the currently camped cell does not support the emergency call.

S415: The GSM MM module sends a radio resource and mobility management termination session notification instruction (RRMM_END_SESSION_NOTIFY) to the GSM AS module.

The radio resource and mobility management termination session notification instruction is used to instruct the terminal device to terminate the session. From the perspective of the user experience, the terminal device directly hangs up the call, resulting in dropped calls.

FIG. 5 is a method for establishing a call according to an embodiment of the present invention. As shown in the figure, S501-S502 in FIG. 5 and S401-S402, S504-S506 and FIG. 4 in FIG. S404-S406 in the embodiment is the same, the difference is:

S503, the LTE module of the terminal device sends a redirection instruction (ID_LRRC_GRR_REDIRECTED_REQ) to the GSM access layer module of the terminal device;

The redirecting instruction includes, in addition to the carrier frequency parameter received from the network device, an emergency call indication, such as a CS emergency call indication, indicating that the type of service to be performed is an emergency call.

After the GSM PHY module of the terminal device transmits the information of the GSM cell that meets the preset condition to the GSM AS module of the terminal device, the GSM AS module does not immediately determine a camping cell from the GSM cell that meets the preset condition. The GSM cell that satisfies the preset condition is firstly determined to support the emergency call service (the embodiment of the present invention does not limit the judgment order). For example, as shown in S507, the GSM AS module determines whether one of the GSM cells that meets the preset condition supports the emergency call service, and the determining method includes but is not limited to:

The GSM AS module determines whether the current GSM cell supports the emergency call service according to the received system information of the current GSM cell broadcast. The GSM AS module reads the "allow emergency call" in the random access channel control parameter (RACH Control Parameters) in the system information category (SYSTEM INFORMATION TYPE) 1, 2, 2bis, 3, or 4 of the current GSM cell broadcast. :Emergency Call allowed, referred to as: EC) field value, when the EC value is 0, or the EC value is 1, and the access class of the terminal device belongs to the category 11-15, the current GSM cell support is judged. Emergency call service; when the EC value is 1, and the access category of the terminal device does not belong to the category 11-15, it is determined that the current GSM cell does not support the emergency call service (refer to the GSM and LTE related to the access category of the terminal device) Standards, for example, access category 11 is for PLMN use, access category 12 is security services, access category 13 is public Utilities, and access category 14 is emergency (Emergency) The access category 15 is a PLMN staff, which is not described in the embodiment of the present invention.

If the current GSM cell supports the emergency call service, the GSM AS module proceeds to perform S508a, that is, determines the camped cell. When determining the camping cell, first, the GSM AS module determines whether the current GSM cell is a suitable cell. For example, the GSM AS module determines whether the ID of the PLMN to which the current GSM cell belongs and the ID of the PLMN currently registered by the terminal device or the ID of the equivalent PLMN are the same according to the information sent by the GSM PHY module. If they are the same, the GSM cell is determined to be a suitable cell. And the GSM cell is used as a camping cell; if different, the GSM cell is determined to be an acceptable cell. The equivalent PLMN and the PLMN currently registered by the terminal device belong to the same operator. When the GSM AS module determines that the current GSM cell is a suitable cell, the current GSM cell can be determined as a camping cell. When the GSM AS module determines that the current GSM cell is an acceptable cell, the GSM AS module continues to execute S508b, that is, the judgment is performed. Whether a GSM cell supports emergency call services. When there is no suitable cell in the GSM cell that meets the preset condition and supports the emergency call service, or is an acceptable cell, the GSM AS module selects one of them or the one with the strongest received signal power as the camping cell.

If the current GSM cell does not support the emergency call service, the GSM AS module continues to perform S508b, that is, whether the next GSM cell supports the emergency call service. If none of the GSM cells satisfying the preset condition supports the emergency call service, S504-S507 is re-executed.

Optionally, when determining that the current GSM cell supports the emergency call service, the GSM AS module omits the step of determining whether the current GSM cell is a suitable cell, and directly determines the current GSM cell as the camped cell. In this case, the terminal device does not need to read the system information of the current GSM cell to obtain the PLMN ID of the current GSM cell, which can save the time for determining the camped cell and speed up the camping speed.

Next, S509-S514 is the same as S408-S413 in FIG. 4 and its corresponding embodiment, except that, as shown in S515, the GSM AS module of the terminal device sends a radio resource connection establishment confirmation to the GSM MM module, including the establishment result. To establish a success (result=EST success) message, it is used to indicate that the radio resource connection is successfully established for the emergency call in the current camping cell. As shown in S516, the GSM MM module sends a connection management service request (CM Service Request) to the network device in the GSM network to request to establish an emergency call. The subsequent UE successfully establishes an emergency call on the GSM network.

FIG. 6 is another method for establishing a call according to an embodiment of the present invention. As shown in the figure, S601-S613 in FIG. 6 is the same as S401-S413 in FIG. 4 and its corresponding embodiment, except that, as shown in FIG. After receiving the radio resource connection establishment request command sent by the GSM MM module, the GSM AS module of the terminal device determines whether the current camped cell supports the emergency call service. The GSM AS module can determine whether the current camped cell supports emergency call services in the following two ways:

1. The GSM AS module determines whether the current camped cell supports the emergency call service according to the received system information of the currently camped cell. The GSM AS module reads "Allow emergency calls" in the random access channel control parameters (RACH Control Parameters) in the system information category (SYSTEM INFORMATION TYPE) 1, 2, 2bis, 3, or 4 of the currently camped cell broadcast ( English: The value of the Emergency Call allowed (EC) field. When the EC value is 0, or the EC value is 1, and the access class of the terminal device belongs to the category 11-15, the current resident is judged. The cell supports the emergency call service; when the EC value is 1, and the access category of the terminal device does not belong to the category 11-15, it is determined that the current camped cell does not support the emergency call service;

2. When the history of the terminal device has been stored in the current camping cell and the information of the current camping cell is supported (Access-Restriction-Emergency-Service), the current station can be judged by checking the information. Whether the staying cell supports emergency call services.

When the GSM AS module determines that the current camping cell does not support the emergency call service, as shown in S615, the GSM AS module determines a new camped cell. The GSM AS module may determine a new resident in the GSM cell that meets the preset condition acquired in S606, or by re-executing the new GSM cell that satisfies the preset condition acquired by S604-S606, by the method as described in S508a. Leave the cell and perform the next steps:

S616: The GSM AS module of the terminal device sends a cell resident instruction to the GSM PHY module to instruct the GSM PHY module to control the terminal device to camp on the selected cell;

S617: The GSM PHY module sends a cell resident confirmation to the GSM AS module.

S618: The GSM AS module of the terminal device sends a radio resource connection establishment confirmation to the GSM MM module, where the establishment result is the establishment success information, and is used to indicate that the radio resource connection is successfully established for the emergency call in the current camping cell;

S619: The GSM MM module sends a connection management service request to the network device in the GSM network to request to establish an emergency call. The subsequent UE successfully establishes an emergency call on the GSM network.

In the embodiment of the present invention, before establishing an emergency call, the terminal device determines whether the current camped cell supports the emergency call service, and when it finds that the current camped cell does not support the emergency call service, re-determines a new resident that supports the emergency call service. The cell improves the success rate of establishing an emergency call in the terminal device CSFB.

In the embodiment of the present invention, the terminal device 200 shown in FIG. 2 or FIG. 3 can perform the call setup method shown in FIG. 5, including:

At least one transceiver 220 is configured to:

Transmitting a first request message to a network device in the first communication network, wherein the terminal device is currently camped on the first communication network, the first request message including emergency call indication information; optionally, the step is performed by LTE in the processor 212 Module 2122 triggers transceiver 220 to execute;

Receiving a first response message sent by the network device, where the first response message includes a carrier frequency parameter;

Sending a second request message to the network device in the second communication network, where the second request message is used to request to establish an emergency call; optionally, the step is triggered by the GSM MM module 2121 in the processor 212 to trigger the transceiver 220;

Processing circuit 212, coupled to at least one transceiver 220, is configured to control the terminal device to:

The first cell is measured, wherein the first cell includes at least one cell in the second communication network and a cell whose carrier frequency parameter satisfies a preset relationship; optionally, the step is performed by the GSM PHY module 2123 in the processor 212. ;

Determining whether the second cell supports emergency call service, where the second cell is a cell in the first cell; optionally, the step is performed by the GSM AS module 2124 in the processor 212;

When the second cell supports the emergency call service, it camps on the second cell.

Optionally, the processing circuit 212 is configured to control the terminal device to further:

When the second cell does not support the emergency call service, it is determined whether the third cell supports the emergency call service, where the third cell is a cell other than the second cell in the first cell. Optionally, this step is performed by GSM AS module 2124 in processor 212.

Optionally, determining whether the second cell supports the emergency call service includes:

When the emergency call EC value in the system information broadcasted by the second cell is 0, or

When the emergency call EC value in the system information broadcasted by the second cell is 1 and the access category of the terminal device belongs to the category 11-15, determining that the second cell supports the emergency call service;

When the emergency call EC value in the system information broadcasted by the second cell is 1 and the access category of the terminal device does not belong to the category 11-15, it is determined that the second cell does not support the emergency call service.

Optionally, this step is performed by GSM AS module 2124 in processor 212.

Determining whether the ID of the public land mobile network PLMN to which the second cell belongs is the same as the first PLMN ID or the second PLMN ID. When the ID of the PLMN to which the second cell belongs is the same as the first PLMN ID or the second PLMN ID, the camp is triggered to The step of the second cell, where the first PLMN ID is the ID of the PLMN currently registered by the terminal device, and the second PLMN ID is the ID of the PLMN equivalent to the PLMN currently registered by the terminal device. Optionally, this step is performed by GSM AS module 2124 in processor 212.

When the ID of the PLMN to which the second cell belongs is different from the first PLMN ID or the second PLMN ID, determining whether the second cell is the cell with the strongest received signal power in the cell in the first cell that meets the preset condition, when When the second cell is the cell with the strongest received signal power in the cell that meets the preset condition in the first cell, the step of camping on the second cell is triggered. Optionally, this step is performed by GSM AS module 2124 in processor 212.

Optionally, the first communication network is a long term evolution LTE network, and the second communication network is a global mobile communication system GSM network.

In the embodiment of the present invention, the terminal device 200 shown in FIG. 2 or FIG. 3 can also perform the call setup method shown in FIG. 6, including:

At least one transceiver 220 is configured to:

Residing to the second cell, where the second cell is one of the first cells;

Determining whether the second cell supports emergency call service; optionally, the step is performed by the GSM AS module 2124 in the processor 212;

When the second cell does not support the emergency call service, it is determined whether the third cell supports the emergency call service, where the third cell is a cell other than the second cell in the first cell; optionally, the step is performed by the processor 212. GSM AS module 2124 is executed;

When the third cell supports the emergency call service, the third cell is reselected.

Optionally, this step is performed by GSM AS module 2124 in processor 212.

Determining, according to the saved historical information, whether the second cell supports the emergency call service, where the historical information is that the second cell acquired by the system information broadcasted by the second cell supports the emergency when the terminal device is historically camped on the second cell. Information about calling services. Optionally, this step is performed by GSM AS module 2124 in processor 212.

It will be understood by those skilled in the art that in the above embodiments, it may be implemented in whole or in part by software, hardware, firmware or any combination thereof. When implemented in software, it may be implemented in whole or in part in the form of a computer program product. The computer program product includes one or more computer instructions. When the computer program instructions are loaded and executed on a computer, the processes or functions described in accordance with embodiments of the present invention are generated in whole or in part. The computer can be a general purpose computer, a special purpose computer, a computer network, or other programmable device. The computer instructions can be stored in a computer readable storage medium or transferred from one computer readable storage medium to another computer readable storage medium, for example, the computer instructions can be from a website site, computer, server or data center Transfer to another website site, computer, server, or data center by wire (eg, coaxial cable, fiber optic, digital subscriber line (DSL), or wireless (eg, infrared, wireless, microwave, etc.). The computer readable storage medium can be any available media that can be accessed by a computer or a data storage device such as a server, data center, or the like that includes one or more available media. The usable medium may be a magnetic medium (eg, a floppy disk, a hard disk, a magnetic tape), an optical medium (eg, a DVD), or a semiconductor medium (such as a solid state disk (SSD)).

Claims

A method for establishing a call, the method being applied to a terminal device, comprising:

Sending a first request message to a network device in the first communication network, where the terminal device is currently camped on a cell in the first communication network, and the first request message includes emergency call indication information;

Receiving a first response message sent by the network device, where the first response message includes a carrier frequency parameter in a second communication network;

Measure the first cell, where the first cell includes at least one cell in the second communication network, and a carrier frequency and a carrier frequency parameter of each cell in the first cell meet a preset relationship. ;

Determining whether the second cell supports emergency call service, where the second cell is one of the first cells;

Retaining to the second cell when the second cell supports the emergency call service;

Sending a second request message to the network device in the second communication network, wherein the second request message is used to request to establish an emergency call.
The method of claim 1 further comprising:

When the second cell does not support the emergency call service, it is determined whether the third cell supports the emergency call service, where the third cell is a cell other than the second cell in the first cell.
The method according to claim 1 or 2, wherein the determining whether the second cell supports the emergency call service comprises:

Allowing the emergency call EC value in the system information broadcast by the second cell to be 0, or

When the emergency call EC value in the system information broadcast by the second cell is 1 and the access category of the terminal device belongs to the category 11-15, determining that the second cell supports the emergency call service;

When the emergency call EC value in the system information broadcasted by the second cell is 1 and the access category of the terminal device does not belong to the category 11-15, it is determined that the second cell does not support the emergency call service.
The method according to any one of claims 1-3, wherein before the camping to the second cell, the method further includes:

Determining whether the ID of the public land mobile network PLMN to which the second cell belongs is the same as the first PLMN ID or the second PLMN ID, and when the ID of the PLMN to which the second cell belongs is the same as the first PLMN ID or the second PLMN ID, And triggering the step of camping to the second cell, where the first PLMN ID is an ID of a PLMN currently registered by the terminal device, and the second PLMN ID is equal to a PLMN currently registered by the terminal device The ID of the valid PLMN.
The method of claim 4, wherein the method further comprises:

When the ID of the PLMN to which the second cell belongs is different from the first PLMN ID or the second PLMN ID, determining whether the second cell is the most received signal power in the cell in the first cell that meets the preset condition A strong cell, when the second cell is a cell that receives the strongest signal power in the cell that meets the preset condition in the first cell, triggers the step of camping to the second cell.
The method according to any of claims 1-5, wherein the first communication network is a Long Term Evolution (LTE) network and the second communication network is a Global System for Mobile Communications (GSM) network.
A method for establishing a call, the method being applied to a terminal device, comprising:

Sending a first request message to a network device in the first communication network, where the terminal device is currently camped on a cell in the first communication network, and the first request message includes emergency call indication information;

Receiving a first response message sent by the network device, where the first response message includes a carrier frequency parameter in a second communication system;

Measure the first cell, where the first cell includes at least one cell in the second communication network, and a carrier frequency and a carrier frequency parameter of each cell in the first cell satisfy a preset relationship;

Residing to a second cell, where the second cell is one of the first cells;

Determining whether the second cell supports an emergency call service;

When the second cell does not support the emergency call service, determining whether the third cell supports the emergency call service, where the third cell is one of the first cell except the second cell that meets the preset Conditional cell;

When the third cell supports the emergency call service, reselecting to the third cell;

Sending a second request message to the network device in the second communication network, wherein the second request message is used to request to establish an emergency call.
The method according to claim 7, wherein the determining whether the second cell supports the emergency call service comprises:

Allowing the emergency call EC value in the system information broadcast by the second cell to be 0, or

When the emergency call EC value in the system information broadcast by the second cell is 1 and the access category of the terminal device belongs to the category 11-15, determining that the second cell supports the emergency call service;

When the emergency call EC value in the system information broadcasted by the second cell is 1 and the access category of the terminal device does not belong to the category 11-15, it is determined that the second cell does not support the emergency call service.
The method according to claim 7, wherein the determining whether the second cell supports the emergency call service comprises:

Determining, according to the saved historical information, whether the second cell supports an emergency call service, where the historical information is a system information that is broadcast by the second cell when the terminal device is historically camped on the second cell. Whether the acquired second cell supports information of an emergency call service.
The method according to any one of claims 7-9, wherein before the camping to the second cell, the method further includes:

Determining whether the ID of the public land mobile network PLMN to which the second cell belongs is the same as the first PLMN ID or the second PLMN ID, and when the ID of the PLMN to which the second cell belongs is the same as the first PLMN ID or the second PLMN ID, And triggering the step of camping to the second cell, where the first PLMN ID is an ID of a PLMN currently registered by the terminal device, and the second PLMN ID is equal to a PLMN currently registered by the terminal device The ID of the valid PLMN.
The method of claim 10, wherein the method further comprises:

When the ID of the PLMN to which the second cell belongs is different from the first PLMN ID or the second PLMN ID, determining whether the second cell is the most received signal power in the cell in the first cell that meets the preset condition A strong cell, when the second cell is a cell that receives the strongest signal power in the cell that meets the preset condition in the first cell, triggers the step of camping to the second cell.
The method according to any one of claims 7 to 11, wherein the first communication network is a Long Term Evolution (LTE) network and the second communication network is a Global System for Mobile Communications (GSM) network.
A terminal device, comprising:

At least one transceiver configured to:

Sending a first request message to a network device in the first communication network, where the terminal device is currently camped on the first communication network, and the first request message includes emergency call indication information;

Receiving a first response message sent by the network device, where the first response message includes a carrier frequency parameter in a second communication network;

Transmitting, to the network device in the second communication network, a second request message, where the second request message is used to request to establish an emergency call;

Processing circuitry coupled to the at least one transceiver, the processing circuitry configured to control the terminal device to:

Measure the first cell, where the first cell includes at least one cell in the second communication network, and a carrier frequency and a carrier frequency parameter of each cell in the first cell meet a preset relationship. ;

Determining whether the second cell supports emergency call service, where the second cell is one of the first cells;

When the second cell supports the emergency call service, camping on the second cell.
The terminal device according to claim 13, wherein said processing circuit is configured to control said terminal device to further:

When the second cell does not support the emergency call service, it is determined whether the third cell supports the emergency call service, where the third cell is a cell of the first cell except the second cell.
The terminal device according to claim 13 or 14, wherein the determining whether the second cell supports the emergency call service comprises:

Allowing the emergency call EC value in the system information broadcast by the second cell to be 0, or

When the emergency call EC value in the system information broadcast by the second cell is 1 and the access category of the terminal device belongs to the category 11-15, determining that the second cell supports the emergency call service;

When the emergency call EC value in the system information broadcasted by the second cell is 1 and the access category of the terminal device does not belong to the category 11-15, it is determined that the second cell does not support the emergency call service.
The terminal device according to any one of claims 13 to 15, wherein the processing circuit is configured to control the terminal device to further:

Determining whether the ID of the public land mobile network PLMN to which the second cell belongs is the same as the first PLMN ID or the second PLMN ID, and when the ID of the PLMN to which the second cell belongs is the same as the first PLMN ID or the second PLMN ID, And triggering the step of camping to the second cell, where the first PLMN ID is an ID of a PLMN currently registered by the terminal device, and the second PLMN ID is equal to a PLMN currently registered by the terminal device The ID of the valid PLMN.
The terminal device according to claim 16, wherein said processing circuit is configured to control said terminal device to further:

When the ID of the PLMN to which the second cell belongs is different from the first PLMN ID or the second PLMN ID, determining whether the second cell is the most received signal power in the cell in the first cell that meets the preset condition A strong cell, when the second cell is a cell that receives the strongest signal power in the cell that meets the preset condition in the first cell, triggers the step of camping to the second cell.
The terminal device according to any one of claims 13-17, wherein the first communication network is a long term evolution LTE network, and the second communication network is a global mobile communication system GSM network.
A terminal device, comprising:

At least one transceiver configured to:

Sending a first request message to a network device in the first communication network, where the terminal device is currently camped on the first communication network, and the first request message includes emergency call indication information;

Receiving a first response message sent by the network device, where the first response message includes a carrier frequency parameter in a second communication network;

Transmitting, to the network device in the second communication network, a second request message, where the second request message is used to request to establish an emergency call;

Processing circuitry coupled to the at least one transceiver, the processing circuitry configured to control the terminal device to:

Measure the first cell, where the first cell includes at least one cell in the second communication network, and a carrier frequency and a carrier frequency parameter of each cell in the first cell meet a preset relationship. ;

Residing to a second cell, where the second cell is one of the first cells;

Determining whether the second cell supports an emergency call service;

When the second cell does not support the emergency call service, it is determined whether the third cell supports the emergency call service, where the third cell is a cell other than the second cell in the first cell;

When the third cell supports the emergency call service, camping on the third cell.
The terminal device according to claim 19, wherein the determining whether the second cell supports the emergency call service comprises:

Allowing the emergency call EC value in the system information broadcast by the second cell to be 0, or

When the emergency call EC value in the system information broadcast by the second cell is 1 and the access category of the terminal device belongs to the category 11-15, determining that the second cell supports the emergency call service;

When the emergency call EC value in the system information broadcasted by the second cell is 1 and the access category of the terminal device does not belong to the category 11-15, it is determined that the second cell does not support the emergency call service.
The terminal device according to claim 19, wherein the determining whether the second cell supports the emergency call service comprises:

Determining, according to the saved historical information, whether the second cell supports an emergency call service, where the historical information is a system information that is broadcast by the second cell when the terminal device is historically camped on the second cell. Whether the acquired second cell supports information of an emergency call service.
The terminal device according to any one of claims 19 to 21, wherein the processing circuit is configured to control the terminal device to further:

Determining whether the ID of the public land mobile network PLMN to which the second cell belongs is the same as the first PLMN ID or the second PLMN ID, and when the ID of the PLMN to which the second cell belongs is the same as the first PLMN ID or the second PLMN ID, And triggering the step of camping to the second cell, where the first PLMN ID is an ID of a PLMN currently registered by the terminal device, and the second PLMN ID is equal to a PLMN currently registered by the terminal device The ID of the valid PLMN.
The terminal device according to claim 22, wherein said processing circuit is configured to control said terminal device to further:

When the ID of the PLMN to which the second cell belongs is different from the first PLMN ID or the second PLMN ID, determining whether the second cell is the most received signal power in the cell in the first cell that meets the preset condition A strong cell, when the second cell is a cell that receives the strongest signal power in the cell that meets the preset condition in the first cell, triggers the step of camping to the second cell.
The terminal device according to any one of claims 19 to 23, wherein the first communication network is a long term evolution LTE network, and the second communication network is a global mobile communication system GSM network.