Method for keeping voice call continuity, device, and computer-readable storage medium

Abstract

Provided in the embodiments of the present application are a method for keeping voice call continuity, an electronic device and a computer-readable storage medium. The method comprises: when a terminal does not log out the IP multimedia subsystem (IMS) domain, prohibiting the terminal from registering the circuit switching (CS) domain; and, after the terminal logs out the IMS domain, allowing the terminal to register the CS domain.

Description

Method, device and computer-readable storage medium for maintaining voice call continuity

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to a Chinese patent application filed with the China Patent Office on June 15, 2023, with application number 202310717278.X and invention name “Method, device and computer-readable storage medium for maintaining voice call continuity”. The entire contents of the Chinese patent application are incorporated herein by reference. Technical Field

[0003] This document relates to the field of mobile communication technology, and more particularly to a method, device, and computer-readable storage medium for maintaining voice call continuity. Background Art

[0004] Currently, after a Voice over Long-Term Evolution (VoLTE) user accesses a 4G network, they are registered on both the 4G and 2G networks simultaneously. This allows the user to maintain voice call service continuity when moving between the 4G and 2G networks.

[0005] This situation where VoLTE users are online on both the 2G and 4G networks simultaneously can maintain the continuity of voice call services, but there is also a waste of network resources, which needs to be improved.

[0006] Summary of the Invention

[0007] Embodiments of the present application provide a method, device, and computer-readable storage medium for maintaining voice call continuity, which are used to solve the problem of network resource waste in current solutions for maintaining voice call continuity.

[0008] In a first aspect, a method for maintaining voice call continuity is provided, which is performed by a mobility management entity (MME). The method includes: prohibiting the terminal from registering in a circuit switched (CS) domain if the terminal has not deregistered from an IP multimedia subsystem (IMS) domain; and allowing the terminal to register in the CS domain after the terminal deregisters from the IMS domain.

[0009] According to a second aspect, a method for maintaining voice call continuity is provided, which is performed by a first device, wherein the first device includes an evolved packet core network EPC or a home subscriber server HSS, and the method includes: in the process of registering the terminal in the IP multimedia subsystem IMS domain, updating the session switching number STN-SR stored in itself to a first STN-SR, and sending the first STN-SR to the mobile management entity MME, wherein the first STN-SR is different from the preset STN-SR, and the first STN-SR is allocated to the terminal by the access transfer control function ATCF or the service centralization and continuity application server SCC AS, and the MME is used to prohibit the terminal from registering for the circuit switched CS domain when confirming that the first STN-SR is different from the preset STN-SR; after successfully responding to the IMS domain deregistration request of the terminal, resetting the STN-SR stored in itself to a second STN-SR, and sending the second STN-SR to the MME, wherein the second STN-SR is the same as the preset STN-SR, and the MME is used to allow the terminal to register for the CS domain when confirming that the second STN-SR is the same as the preset STN-SR.

[0010] According to a third aspect, a method for maintaining voice call continuity is provided, which is executed by a second device, wherein the second device includes an access transfer control function ATCF or a service centralization and continuity application server SCC AS, and the method includes: after receiving a request for a terminal to register an IP multimedia subsystem IMS domain, if it is confirmed that the home network of the terminal supports a single wireless voice call continuity SRVCC function, a first STN-SR session change number is allocated to the terminal, wherein the first STN-SR is different from the preset STN-SR, and the first STN-SR is used to prohibit the terminal from registering for a circuit switched CS domain through a mobile management entity MME when the terminal registers for the IMS domain, and the preset STN-SR is used to allow the terminal to register for the CS domain through the MME when the terminal cancels the IMS domain.

[0011] In a fourth aspect, a method for maintaining voice call continuity is provided, comprising: after receiving a request from a terminal to register with an IP Multimedia Subsystem IMS domain, if it is confirmed that the home network of the terminal supports a single radio voice call continuity SRVCC function, a first session switching number STN-SR is allocated to the terminal, wherein the first STN-SR is different from a preset STN-SR, and the second device includes an access transfer control function ATCF or a service centralization and continuity application server SCC AS; the first device receives the SCC in the process of the terminal registering with the IMS domain. The AS reports the first STN-SR, updates its own stored STN-SR to the first STN-SR, and sends the first STN-SR to the mobile management entity MME, and the first device includes an evolved packet core network EPC or a home subscriber server HSS; when the MME confirms that the first STN-SR is different from the preset STN-SR, the terminal is prohibited from registering for the circuit switched CS domain; after successfully responding to the IMS domain deregistration request of the terminal, the first device resets its own stored STN-SR to the second STN-SR, and sends the second STN-SR to the MME; when the MME confirms that the second STN-SR is the same as the preset STN-SR, the terminal is allowed to register for the CS domain.

[0012] In a fifth aspect, a system for maintaining voice call continuity is provided, comprising: a second device for, after receiving a request from a terminal to register with an IP Multimedia Subsystem IMS domain, allocating a first session switching number STN-SR to the terminal if it is confirmed that the home network of the terminal supports a single radio voice call continuity SRVCC function, wherein the first STN-SR is different from a preset STN-SR, and the second device includes an access transfer control function ATCF or a service centralization and continuity application server SCC AS; a first device for receiving an SCC during the process of the terminal registering with the IMS domain The AS reports the first STN-SR, updates the STN-SR stored in itself to the first STN-SR, and sends the first STN-SR to the mobile management entity MME; and after successfully responding to the IMS domain deregistration request of the terminal, resets the STN-SR stored in itself to the second STN-SR, and sends the second STN-SR to the MME, the first device includes an evolved packet core network EPC or a home subscriber server HSS; the MME is used to prohibit the terminal from registering for the CS domain when it is confirmed that the first STN-SR is different from the preset STN-SR, and allow the terminal to register for the CS domain when it is confirmed that the second STN-SR is the same as the preset STN-SR.

[0013] In a sixth aspect, an electronic device is provided, comprising: a processor; and a memory for storing instructions executable by the processor; wherein the processor is configured to execute the instructions to implement the method described in the first aspect.

[0014] In a seventh aspect, a computer-readable storage medium is provided, which, when the instructions in the storage medium are executed by a processor of an electronic device, enables the electronic device to execute the method as described in any one of the first, second and third aspects. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments recorded in this application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative labor.

[0016] FIG1 is a voice routing process when 2G and 4G are online simultaneously in the related art.

[0017] FIG2 is a voice routing process for 2G and 4G networks that are online simultaneously, provided in an embodiment of the present application.

[0018] FIG3 is a flow chart of a method for maintaining voice call continuity provided by an embodiment of the present application.

[0019] FIG4 is a flow chart of a method for maintaining voice call continuity provided by another embodiment of the present application.

[0020] FIG5 is a flowchart of a method for maintaining voice call continuity provided by another embodiment of the present application.

[0021] FIG6 is a flowchart of a method for maintaining voice call continuity provided by another embodiment of the present application.

[0022] FIG7 is a schematic structural diagram of an electronic device according to an embodiment of the present application.

[0023] FIG8 is a schematic structural diagram of an apparatus for maintaining voice call continuity provided by an embodiment of the present application.

[0024] FIG9 is a schematic structural diagram of an apparatus for maintaining voice call continuity provided by another embodiment of the present application.

[0025] FIG10 is a schematic structural diagram of an apparatus for maintaining voice call continuity provided by another embodiment of the present application. DETAILED DESCRIPTION

[0026] In order to enable those skilled in the art to better understand the technical solutions in the embodiments of this application, the technical solutions in the embodiments of this application will be clearly and completely described below in conjunction with the drawings in one or more embodiments of this application. Obviously, the described embodiments are only part of the embodiments of this application, not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative efforts should fall within the scope of protection of this document.

[0027] The terms "first," "second," etc., in this application and the claims are used to distinguish similar objects and are not used to describe a particular order or precedence. It should be understood that the numerals used in this manner are interchangeable where appropriate so that the embodiments of the present application can be implemented in an order other than those illustrated or described herein. In addition, the term "and / or" in this application and the claims represents at least one of the connected objects, and the character " / " generally represents that the objects associated with each other are in an "or" relationship.

[0028] In order to better illustrate the technical solutions provided by the embodiments of the present application, the relevant technologies and terms involved in the embodiments of the present application are explained below.

[0029] Second Generation (2G) mobile communication technology is a cellular mobile communication technology. User Equipment (UE) primarily accesses 2G networks and obtains services through wireless air interfaces. UEs exchange information with base stations over the air interfaces and access the core network wirelessly. In 2G networks, UEs are also called Mobile Stations (MS).

[0030] The Mobile Switching Center (MSC) is used to provide call control, mobility management, authentication, and encryption functions in the Circuit Switched (CS) domain.

[0031] The Serving GPRS Support Node (SGSN) is used to provide routing forwarding, mobility management, session management, authentication and encryption functions in the Packet Service (PS) domain.

[0032] The 3rd Generation Partnership Project (3GPP) began developing the Long Term Evolution (LTE) mobile communications system in Release 8. In LTE, a user equipment (UE) accesses the 4G network and obtains services through the wireless air interface. The UE exchanges information with the base station over the air interface and with the mobility management entity of the core network through non-access stratum (NAS) signaling.

[0033] Evolved Packet Core (EPC) is the evolved packet core network and the core network of 4G LTE.

[0034] The Mobile Management Entity (MME) is a core network control plane entity responsible for user authentication, authorization, and subscription checks, user mobility management, Packet Data Network (PDN) connection and bearer maintenance, and triggering paging in the user IDLE state.

[0035] The Home Subscription Server (HSS) stores the user's subscription information, including authentication, services, etc.

[0036] According to the 3GPP definition, 4G systems already support the IP Multimedia Core Network Subsystem (IMS). IMS enables IP-based multimedia sessions, including voice, video, and other multimedia services. The main functional entities in the IMS system include the Proxy Call Session Control Function (P-CSCF), the Interrogating Call Session Control Function (I-CSCF), the Serving Call Session Control Function (S-CSCF), the Access Transfer Control Function (ATCF), and the Application Server (AS).

[0037] In the early stages of LTE network construction or when LTE network coverage is insufficient, when a user making a voice call on the LTE network moves to an area with weak LTE signal and good 2G wireless signal coverage, 3GPP has proposed a VoLTE voice service continuity solution, Single Radio Voice Call Continuity (SRVCC), to ensure voice call continuity (VCC) for the Long Term Evolution (LTE) network voice service. This solution, called Single Radio Voice Call Continuity (SRVCC), allows the IMS to smoothly switch between VoIP and CS domain voice when the UE moves between the LTE and 2G networks. Figure 1 shows a schematic diagram of the voice routing process for simultaneous 2G and 4G connections in the related art.

[0038] In addition, the embodiments of the present application also involve the following terms (terms not listed here will be supplemented in the necessary places below):

[0039] Session Transfer Number for SRVCC (STN-SR);

[0040] Service Call Continuity Application Server (SCC AS)

[0041] The Session Initiation Protocol (SIP) was developed by the Internet Engineering Task Force (IETF) for multi-party multimedia communications. As defined in IETF RFC 2543, SIP is a text-based application layer control protocol, independent of the underlying transport protocols TCP / UDP / SCTP, used to establish, modify, and terminate two-party or multi-party multimedia sessions over IP networks.

[0042] 1 , the voice routing process for simultaneous online 2G and 4G in the related art is described below.

[0043] As shown in Figure 1, the voice routing process for both 2G and 4G networks may include (briefly described below):

[0044] (1) EPC attachment process:

[0045] Step 101: MME sends an Update Location Request (ULR) message to EPC.

[0046] Generally speaking, the ULR carries the International Mobile Subscriber Identity (IMSI) of the UE and the SRVCC capability of the UE.

[0047] Step 102: When the EPC confirms that the UE supports SRVCC, it returns a location update response (ULA) to the MME. The ULA carries the STN-SR determined according to the user's subscription.

[0048] Specifically, when the UE initiates the EPC attach process, the UE will indicate whether it supports SRVCC in the MS Network Capability parameter in the sent Attach Request message. After receiving the UE's attach request, the MME confirms whether the UE supports SRVCC. If so, it executes step 101 above.

[0049] (2) IMS domain registration

[0050] Step 103: When the UE registers in the IMS domain (SIP register) through the ATCF, if the UE's home network supports SRVCC function enhancement using the ATCF, the ATCF allocates an STN-SR according to the operator's policy and sends it to the SCC AS through a SIP message.

[0051] Optionally, if the ATCF does not allocate the STN-SR, the SCC AS allocates the STN-SR.

[0052] Step 104: The SCC AS sends a User Data Request (UDR) message to the HSS to obtain the STN-SR stored by the HSS for the UE. The SCC AS determines whether the STN-SR obtained from the HSS is consistent with the STN-SR allocated by the ATCF or the SCC AS.

[0053] In step 105 , the HSS sends the judgment result in step 104 to the SCC AS via a User Data Answer (UDA); if the judgment result is consistent, execute step 108 ; otherwise, execute step 106 .

[0054] In step 106, the SCC AS sends a Profile-Update-Request (PUR) message to the HSS according to the operator's policy. The PUR carries the STN-SR allocated in step 103, so that the HSS updates the STN-SR. The updated STN-SR is used for subsequent session routing from the IMS domain to the CS domain.

[0055] Step 107: The HSS notifies the EPC to update the STN-SR through an internal message.

[0056] In step 108, the EPC (or HSS) notifies the MME to update the STN-SR via an IDR (Insert-Subscriber-Data-Request) message.

[0057] In step 109, the MME feeds back a response to updating the STN-SR to the EPC (or HSS) via an IDA (Insert-Subscriber-Data-Answer) message.

[0058] Step 110: The EPC notifies the HSS of a response to updating the STN-SR through an internal message.

[0059] In step 111 , the HSS feeds back a response to updating the STN-SR to the SCC AS via a Profile-Update-Answer (PUA) message.

[0060] It should be noted that, in step 104, step 105, step 106 and step 111, the SCC AS and the HSS interact through the Sh interface.

[0061] (3) Originating and terminating call processes during SRVCC handover from 4G to 2G

[0062] Step 112: The MSC receives a handover request from the MME or SGSN via the Sv interface to handover the voice session from the IMS domain to the CS domain.

[0063] Step 113: The MSC sends a handover request message to the ATCF of the visited location through the Mw interface.

[0064] The ATCF of the visited location is determined based on the updated STN-SR, that is, the MSC routes the ATCF using the STN-SR number obtained from the MME or SGSN.

[0065] Step 114: The ATCF sends an Invite message to the SCC AS to switch the voice session.

[0066] In steps 115 to 119, the SCC AS checks whether the UE has SRVCC capability. If the check passes, the SCC AS returns the C-MSISDN to the ATCF to implement subsequent session routing from the IMS domain to the CS domain.

[0067] Among them, the UDR in step 115 carries the International Portable User Identity (PUI) and the port-based VLAN ID (PVI) in network communication; the internal message (Internal Message Req) in step 116 carries the SRVCC capability of the UE; the internal message (Internal Message Ack) in step 117 carries the SRVCC capability of the UE; the UDA in step 118 carries the SRVCC capability of the UE; and the Session Initiation Protocol (SIP) response in step 119 carries the C-MSISDN.

[0068] C-MSISDN stands for Combined MSISDN, a number used to identify mobile users on mobile communication networks. It consists of a country code (CC) and a mobile subscriber number (MSISDN). C-MSISDN is typically used to support multiple SIM card-based services, such as voice, SMS, and data, and allows mobile users to use the same number on different devices. In some wireless communication standards, such as GSM, C-MSISDN is called the Integrated Circuit Card Identifier (ICCID).

[0069] As shown in Figure 1, in related technologies, when a user makes a voice call from the IMS domain, the 2G resources of the CS domain are occupied. When the user falls back from the IMS domain to the CS domain, the 2G resources of the CS domain are also occupied. Regardless of whether the 4G network is online, the 2G resources are always occupied. Although this can ensure the high reliability of voice call continuity, it also causes the problem of resource waste.

[0070] To address this issue, the present application proposes a technical concept: "If a terminal is registered with the IMS domain and has not yet deregistered, prohibiting the terminal from registering in the CS domain, and allowing the terminal to register in the CS domain after deregistering the IMS domain." Based on this technical concept, the present application proposes, for example, a voice routing solution for simultaneous 2G and 4G connections. The process is shown in Figure 2 and is briefly described below.

[0071] As shown in FIG2 , an embodiment of the present application provides a voice routing process for 2G and 4G networks that are both online simultaneously, which may include:

[0072] In step 201, the I-CSCF sends a User-Authorization-Request (UAR) message to the HSS to register with the IMS domain.

[0073] After the UE accesses the 4G network, the VoLTE user will initiate registration in the IMS domain, and the I-CSCF will initiate a UAR service message on the Cx port to the HSS for registration.

[0074] In step 202, the HSS returns a User-Authorization-Answer (UAA) carrying the S-CSCF address to the I-CSCF.

[0075] The S-CSCF address carried in the UAA is dynamic.

[0076] In step 203, the S-CSCF sends a Server-Assignment-Request (SAR) to the HSS to register with the IMS domain and obtain user subscription information.

[0077] Typically, the server assignment type (Server-Assignment-Type, SAT) carried in the SAR is a registration type, that is, SAT=registration.

[0078] In step 204, the HSS returns a Server-Assignment-Answer (SAA) to the S-CSCF, which carries the user subscription information.

[0079] In step 205, the SCC AS sends a user data request (UDR) message to the HSS to obtain the first STN-SR saved by the HSS for the UE. The SCC AS determines whether the first STN-SR obtained from the HSS is consistent with the first STN-SR allocated by the ATCF or the SCC AS.

[0080] The first STN-SR is a non-default STN-SR, that is, the first STN-SR is a non-preset STN-SR (non-default STN-SR).

[0081] In step 206 , the HSS sends the judgment result in step 104 to the SCC AS via a user data answer (UDA); if the judgment result is consistent, execute step 209 ; otherwise, execute step 207 .

[0082] In step 207, the SCC AS sends a Profile-Update-Request (PUR) message to the HSS according to the operator's policy. The PUR carries the first STN-SR allocated by the ATCF or the SCC AS, so that the HSS updates the STN-SR. The updated STN-SR is used for subsequent session routing from the IMS domain to the CS domain.

[0083] In step 208, the HSS feeds back a response to updating the STN-SR to the SCC AS via a Profile-Update-Answer (PUA) message.

[0084] In step 209 , the HSS notifies the MME to update the STN-SR to the first STN-SR through an IDR (Insert-Subscriber-Data-Request) message.

[0085] When the MME confirms that the updated STN-SR is not the preset STN-SR, it prohibits the terminal from registering in the CS domain. Specifically, it can prohibit the terminal from registering in the CS domain by closing the SGs interface between the MME and the mobile service switching center MSC. This can enable the terminal to exit the 2G network when attached to the IMS domain, thereby saving 2G network resources.

[0086] In step 210, the MME feeds back a response to updating the STN-SR to the EPC (or HSS) via an IDA (Insert-Subscriber-Data-Answer) message.

[0087] Step 211: When the user logs out of the IMS domain, the S-CSCF sends a SAR message to the HSS through the Cx interface to deregister from the IMS domain.

[0088] In step 212, when the S-CSCF determines that the SAT in the SAR message is a deregistration type and the IMS domain switch is turned on, it returns a successful deregistration response to the HSS through SAA, and the HSS resets the STN-SR to the second STN-SR, where the second STN-SR is a preset STN-SR (default STN-SR).

[0089] Among them, the cancellation class can be:

[0090] TIMEOUT_DEREGISTRATION,USER_DEREGISTRATION,ADMINISTRATIVE_DEREGISTRATION,DEREGISTRATION_TOO_MUCH_DATA,TIMEOUT_DEREGISTRATION_STORE_SERVER_NAME,USER_DEREGISTRATION_STORE_SERVER_NAME,AUTHENTICATION_FAILURE,AUTHENTICATION_TIMEOUT

[0091] Step 213: The HSS sends the second STN-SR to the MME via an IDR message.

[0092] In step 214 , when the MME determines that the second STN-SR is the preset STN-SR, the MME re-initiates CS domain registration (see steps 215 and 216 ).

[0093] Step 215: The MME notifies the MSC / VLR via the SGs interface to trigger location registration.

[0094] Step 216: The MSC initiates a CS domain location registration to the HLR / HSS to update the location of the terminal in the CS domain.

[0095] As can be seen from Figure 2, a 2G and 4G voice routing process with simultaneous online use provided by an embodiment of the present application, by inserting different STN-SRs into the MME, can prohibit the terminal from registering in the circuit switched CS domain if the terminal has not deregistered the IP multimedia subsystem IMS domain; after the terminal deregisters the IMS domain, the terminal is allowed to register in the CS domain. This allows the terminal to be attached to the IMS domain or the CS domain at the same time, but not at the same time. Therefore, while maintaining the continuity of voice calls, it can reduce the CS domain resources occupied by IMS domain users, effectively promote 2G network withdrawal, reduce the occupation of 2G network resources, and save 2G network resources.

[0096] It should be noted that Figure 2 focuses on describing a voice routing process for 2G and 4G simultaneously online provided in an embodiment of the present application, which is different from the voice routing process for 2G and 4G simultaneously online in the related technology shown in Figure 3. Therefore, some existing steps are omitted.

[0097] Based on the above technical concept, the embodiment of the present application further proposes a method for maintaining voice call continuity, which is described below from the perspectives of different execution entities with reference to the accompanying drawings.

[0098] An embodiment of the present application provides a method for maintaining voice call continuity, which may be performed by an MME. As shown in FIG3 , the method may include:

[0099] Step 301: If the terminal has not deregistered from the IP Multimedia Subsystem (IMS) domain, prohibit the terminal from registering in the Circuit Switched (CS) domain.

[0100] As an example, step 301 may specifically include: receiving a first STN-SR issued by a first device during the process of the terminal registering the IMS domain, wherein the first device includes an EPC or an HSS, and the first STN-SR is different from the preset STN-SR, that is, the first STN-SDR is a non-default STN-SR, and the first STN-SR is allocated to the terminal by the ATCF or SCC AS; when it is confirmed that the first STN-SR is different from the preset STN-SR, the terminal is prohibited from registering the CS domain.

[0101] Of course, it is also possible not to determine whether to prohibit the terminal from registering in the CS domain by "determining whether the first STN-SR issued by the first device is the preset STN-SR", but to directly prohibit the terminal from registering in the CS domain after confirming that the terminal is registered in the IMS domain and has not cancelled the IMS domain.

[0102] Furthermore, the prohibiting the terminal from registering in the CS domain includes: prohibiting the terminal from registering in the CS domain by closing the SGs interface between the MME and a mobile services switching center MSC.

[0103] Step 302: After the terminal deregisters the IMS domain, the terminal is allowed to register the CS domain.

[0104] As an example, step 302 may specifically include: receiving a second STN-SR issued by the first device after successfully responding to the IMS domain deregistration request of the terminal, wherein the second STN-SR is the same as the preset STN-SR; upon confirming that the second STN-SR is the same as the preset STN-SR, allowing the terminal to register for the CS domain.

[0105] Similarly, it is also possible not to determine whether to allow the terminal to register for the CS domain by "determining whether the second STN-SR issued by the first device is the preset STN-SR", but to directly allow the terminal to register for the CS domain after confirming that the terminal has deregistered the IMS domain.

[0106] Furthermore, the allowing the terminal to register in the CS domain may include: allowing the terminal to register in the CS domain by opening an SGs interface between the MME and a mobile services switching center MSC.

[0107] The embodiment shown in Figure 3 provides a voice routing process for simultaneous 2G and 4G connections. This process prohibits a terminal from registering in the Circuit Switched (CS) domain if the terminal has not yet deregistered from the IP Multimedia Subsystem (IMS) domain; after deregistering from the IMS domain, the terminal is allowed to register in the CS domain. This allows for the maintenance of voice call continuity while reducing the CS domain resource usage by IMS users, effectively facilitating 2G network decommissioning and saving 2G network resources.

[0108] Another embodiment of the present application provides a method for maintaining voice call continuity, which may be performed by a first device, the first device including an EPC or an HSS. As shown in FIG4 , the method may include:

[0109] Step 401: During the process of registering the terminal in the IP Multimedia Subsystem IMS domain, the terminal updates its stored session switching number STN-SR to a first STN-SR, and sends the first STN-SR to the Mobility Management Entity MME.

[0110] In which, the first STN-SR is different from the preset STN-SR, and the first STN-SR is allocated to the terminal by the access transfer control function ATCF or the service centralization and continuity application server SCC AS, and the MME is used to prohibit the terminal from registering the CS domain when it is confirmed that the first STN-SR is different from the preset STN-SR.

[0111] Specifically, the MME may prohibit the terminal from registering in the CS domain by closing the SGs interface between the MME and the MSC.

[0112] Among them, updating the STN-SR stored in itself to the first STN-SR may include: receiving the first STN-SR reported by the SCC AS during the process of the terminal registering the IMS domain, wherein the first STN-SR is reported by the SCC AS after confirming that the STN-SR currently stored in the first device is different from the first STN-SR; updating the STN-SR stored in itself to the first STN-SR.

[0113] Step 402: After successfully responding to the IMS domain deregistration request of the terminal, resetting the STN-SR stored in itself to a second STN-SR, and sending the second STN-SR to the MME.

[0114] The second STN-SR is the same as the preset STN-SR, and the MME is configured to allow the terminal to register in the CS domain if it is confirmed that the second STN-SR is the same as the preset STN-SR.

[0115] Specifically, the MME may enable the terminal to register in the CS domain by opening the SGs interface.

[0116] The embodiment shown in Figure 4 provides a voice routing process for 2G and 4G to be online at the same time. Since the first device can send a non-default first STN-SR to the MME during the process of the terminal registering the IMS domain, the MME can prohibit the terminal from registering the CS domain if the terminal has not deregistered the IMS domain; after successfully responding to the IMS domain deregistration request of the terminal, the default second STN-SR is sent to the MME, so that the MME allows the terminal to register the CS domain after the terminal deregisters the IMS domain. Therefore, while maintaining the continuity of voice calls, it is possible to reduce the occupation of CS domain resources by IMS domain users, effectively promote 2G network withdrawal, reduce the occupation of 2G network resources, and save 2G network resources.

[0117] Optionally, before resetting the STN-SR stored in itself to the second STN-SR, the method shown in Figure 4 may also include: receiving an IMS domain deregistration request of the terminal sent by a call session control function CSCF; when the server allocation type SAT carried in the IMS domain deregistration request is a deregistration class and the IMS domain switch is turned on, returning a successful response to the IMS domain deregistration request to the CSCF to confirm that the deregistration is successful.

[0118] Optionally, the method shown in FIG4 may further include: receiving a location update request for the terminal in the CS domain initiated by the MSC, and updating the location of the terminal in the CS domain, wherein the location update request is initiated by the MSC after receiving a location update trigger notification sent by the MME. It is understood that this step can implement SRVCC handover from 4G to 2G.

[0119] Another embodiment of the present application provides a method for maintaining voice call continuity, which may be performed by a second device, the second device including an ATCF or an SCC AS. As shown in FIG4 , the method may include:

[0120] Step 501: after receiving a request from a terminal to register with an IP Multimedia Subsystem (IMS) domain, if it is confirmed that the home network of the terminal supports the Single Radio Voice Call Continuity (SRVCC) function, a first STN-SR session change number is allocated to the terminal.

[0121] Among them, the first STN-SR is different from the preset STN-SR. The first STN-SR is used to prohibit the terminal from registering in the circuit switched CS domain through the mobile management entity MME when the terminal registers in the IMS domain. The preset STN-SR is used to allow the terminal to register in the CS domain through the MME when the terminal cancels the IMS domain.

[0122] The embodiment shown in Figure 5 provides a voice routing process for 2G and 4G simultaneously online. Since the second device can allocate a non-default first STN-SR to the terminal during the process of the terminal registering the IMS domain, the MME prohibits the terminal from registering the CS domain without deregistering the IMS domain. Therefore, while maintaining the continuity of voice calls, the occupation of CS domain resources by IMS domain users can be reduced, effectively promoting 2G network exit, reducing the occupation of 2G network resources, and saving 2G network resources.

[0123] As shown in FIG6 , an embodiment of the present application further provides a method for maintaining voice call continuity, which may include:

[0124] Step 601: After receiving a request from a terminal to register in an IP Multimedia Subsystem (IMS) domain, the second device allocates a first session switching number (STN-SR) to the terminal if it is confirmed that the home network of the terminal supports the Single Radio Voice Call Continuity (SRVCC) function.

[0125] The first STN-SR is different from the preset STN-SR, and the second device includes an access transfer control function ATCF or a service centralization and continuity application server SCC AS.

[0126] Step 602: During the process of terminal registration in the IMS domain, the first device receives the first STN-SR reported by the SCC AS, updates its own stored STN-SR to the first STN-SR, and sends the first STN-SR to the mobility management entity MME.

[0127] The first device includes EPC or HSS.

[0128] Step 603: When the MME confirms that the first STN-SR is different from a preset STN-SR, the MME prohibits the terminal from registering in the circuit switched CS domain.

[0129] Step 604: After successfully responding to the IMS domain deregistration request of the terminal, the first device resets its own stored STN-SR to a second STN-SR and sends the second STN-SR to the MME;

[0130] Step 605: When the MME confirms that the second STN-SR is the same as the preset STN-SR, the MME allows the terminal to register in the CS domain.

[0131] In this embodiment of the present application, if the terminal has not yet deregistered from the IP Multimedia Subsystem (IMS) domain, the terminal can be prohibited from registering in the Circuit Switched (CS) domain; after the terminal deregisters from the IMS domain, the terminal can be allowed to register in the CS domain. This allows the terminal to be attached to either the IMS domain or the CS domain at the same time, rather than simultaneously. Therefore, while maintaining voice call continuity, it can reduce the CS domain resource occupation by IMS domain users, effectively promote 2G network decommissioning, reduce the occupation of 2G network resources, and save 2G network resources.

[0132] Corresponding to the method shown in FIG6 , an embodiment of the present application further provides a system for maintaining voice call continuity, including:

[0133] The second device is configured to allocate a first session switching number STN-SR to the terminal after receiving a request from the terminal to register with the IP Multimedia Subsystem IMS domain, if it is confirmed that the home network of the terminal supports the single radio voice call continuity SRVCC function, wherein the first STN-SR is different from the preset STN-SR, and the second device includes an access transfer control function ATCF or a service centralization and continuity application server SCC AS;

[0134] A first device, configured to receive the first STN-SR reported by the SCC AS during the process of the terminal registering the IMS domain, update the STN-SR stored in itself to the first STN-SR, and send the first STN-SR to the mobility management entity MME; and, after successfully responding to the IMS domain deregistration request of the terminal, reset the STN-SR stored in itself to the second STN-SR, and send the second STN-SR to the MME, wherein the first device includes an evolved packet core network EPC or a home subscriber server HSS;

[0135] The MME is configured to prohibit the terminal from registering for the CS domain when it is confirmed that the first STN-SR is different from the preset STN-SR, and allow the terminal to register for the CS domain when it is confirmed that the second STN-SR is the same as the preset STN-SR.

[0136] This system can achieve the same technical effect as the method shown in Figure 6, and will not be described in detail.

[0137] The foregoing description describes specific embodiments of the present application. Other embodiments are within the scope of the appended claims. In some cases, the actions or steps recited in the claims can be performed in an order different from that described in the embodiments and still achieve the desired results. Furthermore, the processes depicted in the accompanying drawings do not necessarily require the specific order shown or the sequential order to achieve the desired results. In certain embodiments, multitasking and parallel processing are also possible or may be advantageous.

[0138] FIG7 is a schematic diagram of the structure of an electronic device according to an embodiment of the present application. Referring to FIG7 , at the hardware level, the electronic device includes a processor, and optionally also includes an internal bus, a network interface, and a memory. The memory may include a memory, such as a high-speed random access memory (RAM), and may also include a non-volatile memory (non-volatile memory), such as at least one disk storage device. Of course, the electronic device may also include hardware required for other services.

[0139] The processor, network interface, and memory can be interconnected via an internal bus, which can be an Industry Standard Architecture (ISA) bus, a Peripheral Component Interconnect (PCI) bus, or an Extended Industry Standard Architecture (EISA) bus. These buses can be classified as address buses, data buses, control buses, and the like. For ease of illustration, FIG7 shows only one bidirectional arrow, but this does not imply that there is only one bus or only one type of bus.

[0140] The memory is used to store programs. Specifically, the program may include program code, which includes computer operating instructions. The memory may include internal memory and non-volatile memory, and provides instructions and data to the processor.

[0141] The processor reads the corresponding computer program from the non-volatile memory into the internal memory and then runs it, forming a device for maintaining voice call continuity at the logical level. The processor executes the program stored in the memory and is specifically used to perform the following operations:

[0142] If the terminal has not deregistered from the IP Multimedia Subsystem (IMS) domain, prohibiting the terminal from registering in the Circuit Switched (CS) domain;

[0143] After the terminal deregisters the IMS domain, the terminal is allowed to register the CS domain.

[0144] Alternatively, the processor executes the program stored in the memory and is specifically configured to perform the following operations:

[0145] In the process of terminal registration IP Multimedia Subsystem IMS domain, the session switching number STN-SR stored in itself is updated to a first STN-SR, and the first STN-SR is sent to the mobility management entity MME, wherein the first STN-SR is different from the preset STN-SR, and the first STN-SR is allocated to the terminal by the access transfer control function ATCF or the service centralization and continuity application server SCC AS, and the MME is used to prohibit the terminal from registering the circuit switched CS domain when confirming that the first STN-SR is different from the preset STN-SR;

[0146] After successfully responding to the IMS domain deregistration request of the terminal, the STN-SR stored in itself is reset to the second STN-SR, and the second STN-SR is sent to the MME, wherein the second STN-SR is the same as the preset STN-SR, and the MME is used to allow the terminal to register for the CS domain when confirming that the second STN-SR is the same as the preset STN-SR.

[0147] Alternatively, the processor executes the program stored in the memory and is specifically configured to perform the following operations:

[0148] After receiving a request from a terminal to register with the IP Multimedia Subsystem IMS domain, if it is confirmed that the home network of the terminal supports the Single Radio Voice Call Continuity SRVCC function, a first STN-SR session change number is allocated to the terminal, wherein the first STN-SR is different from the preset STN-SR. The first STN-SR is used to prohibit the terminal from registering for the Circuit Switched CS domain through the Mobile Management Entity MME when the terminal registers the IMS domain, and the preset STN-SR is used to allow the terminal to register for the CS domain through the MME when the terminal cancels the IMS domain.

[0149] The method performed by the apparatus for maintaining voice call continuity disclosed in the embodiment shown in FIG. 7 of the present application can be applied to or implemented by a processor. The processor may be an integrated circuit chip with signal processing capabilities. During implementation, each step of the method can be performed by hardware integrated logic circuits or software instructions in the processor. The processor can be a general-purpose processor, including a central processing unit (CPU), a network processor (NP), etc.; it can also be a digital signal processor (DSP), an application-specific integrated circuit (ASIC), a field-programmable gate array (FPGA), or other programmable logic devices, discrete gate or transistor logic devices, or discrete hardware components. The methods, steps, and logic block diagrams disclosed in the embodiments of the present application can be implemented or executed. The general-purpose processor can be a microprocessor or any conventional processor. The steps of the method disclosed in the embodiments of the present application can be directly implemented and executed by a hardware decoding processor, or by a combination of hardware and software modules in the decoding processor. The software module can be located in a storage medium well-known in the art, such as random access memory, flash memory, read-only memory, programmable read-only memory, electrically erasable programmable memory, registers, etc. The storage medium is located in the memory, and the processor reads the information in the memory and, in conjunction with its hardware, completes the steps of the above method.

[0150] The electronic device can also execute the method of Figure 3, Figure 4 or Figure 5, and realize the functions of the device for maintaining voice call continuity in the embodiments shown in Figure 3, Figure 4 or Figure 5, and the embodiments of this application will not be repeated here.

[0151] Of course, in addition to software implementation, the electronic device of this application does not exclude other implementation methods, such as logic devices or a combination of software and hardware, etc. That is to say, the execution subject of the following processing flow is not limited to each logic unit, but can also be hardware or logic devices.

[0152] An embodiment of the present application also proposes a computer-readable storage medium, which stores one or more programs, and the one or more programs include instructions. When the instructions are executed by a portable electronic device including multiple application programs, the portable electronic device can execute the method of the embodiment shown in Figure 3, Figure 4 or Figure 5.

[0153] FIG8 is a schematic diagram of a device 800 for maintaining voice call continuity according to an embodiment of the present application. The device 800 may be applied to an MME. Referring to FIG8 , in a software implementation, the device 800 may include a registration prohibition module 801 and a registration permission module 802.

[0154] The registration prohibition module 801 is configured to prohibit the terminal from registering in the circuit switched CS domain if the terminal has not deregistered from the IP Multimedia Subsystem IMS domain.

[0155] As an example, the registration prohibition module 801 can be specifically used to: receive a first STN-SR issued by a first device during the process of the terminal registering the IMS domain, wherein the first device includes an EPC or an HSS, and the first STN-SR is different from the preset STN-SR, that is, the first STN-SDR is a non-default STN-SR, and the first STN-SR is allocated to the terminal by ATCF or SCC AS; when it is confirmed that the first STN-SR is different from the preset STN-SR, the terminal is prohibited from registering the CS domain.

[0156] Of course, the registration prohibition module 801 may also determine whether to prohibit the terminal from registering in the CS domain without "determining whether the first STN-SR issued by the first device is the preset STN-SR", but directly prohibit the terminal from registering in the CS domain after confirming that the terminal is registered in the IMS domain and has not cancelled the IMS domain.

[0157] Furthermore, the registration prohibition module 801 may prohibit the terminal from registering in the CS domain by closing the SGs interface between the MME and the mobile services switching center MSC.

[0158] The registration allowing module 802 is configured to allow the terminal to register in the CS domain after the terminal deregisters from the IMS domain.

[0159] As an example, the registration prohibition module 801 can be specifically used to: receive a second STN-SR issued by the first device after successfully responding to the IMS domain deregistration request of the terminal, wherein the second STN-SR is the same as the preset STN-SR; and upon confirming that the second STN-SR is the same as the preset STN-SR, allow the terminal to register for the CS domain.

[0160] Similarly, the registration prohibition module 801 may not determine whether to allow the terminal to register the CS domain by "determining whether the second STN-SR issued by the first device is the preset STN-SR", but directly allow the terminal to register the CS domain after confirming that the terminal has deregistered the IMS domain.

[0161] Furthermore, the registration prohibiting module 801 may be specifically configured to allow the terminal to register in the CS domain by opening the SGs interface between the MME and the mobile services switching center MSC.

[0162] An apparatus 800 for maintaining voice call continuity provided in an embodiment of the present application can also execute the method of FIG3 and realize the functions of the apparatus 800 for maintaining voice call continuity in the embodiment shown in FIG3 , which will not be described in detail in this embodiment of the present application.

[0163] FIG9 is a schematic diagram of a structure of an apparatus 900 for maintaining voice call continuity according to an embodiment of the present application. The apparatus 900 can be applied to an MME. Referring to FIG9 , in a software implementation, the apparatus 900 for maintaining voice call continuity can include: a first sending module 901 and a second sending module 902.

[0164] The first sending module 901 is configured to update the session switching number STN-SR stored in itself to a first STN-SR during the process of the terminal registering the IP Multimedia Subsystem IMS domain, and send the first STN-SR to the Mobility Management Entity MME.

[0165] In which, the first STN-SR is different from the preset STN-SR, and the first STN-SR is allocated to the terminal by the access transfer control function ATCF or the service centralization and continuity application server SCC AS, and the MME is used to prohibit the terminal from registering the CS domain when it is confirmed that the first STN-SR is different from the preset STN-SR.

[0166] Specifically, the MME may prohibit the terminal from registering in the CS domain by closing the SGs interface between the MME and the MSC.

[0167] Among them, the first sending module 901 can be specifically used to: receive the first STN-SR reported by the SCC AS during the process of the terminal registering the IMS domain, wherein the first STN-SR is reported by the SCC AS when confirming that the STN-SR currently stored in the first device is different from the first STN-SR; and update the STN-SR stored in itself to the first STN-SR.

[0168] The second sending module 902 is configured to reset the STN-SR stored in itself to a second STN-SR after successfully responding to the IMS domain deregistration request of the terminal, and send the second STN-SR to the MME.

[0169] The second STN-SR is the same as the preset STN-SR, and the MME is configured to allow the terminal to register in the CS domain if it is confirmed that the second STN-SR is the same as the preset STN-SR.

[0170] Specifically, the MME may enable the terminal to register in the CS domain by opening the SGs interface.

[0171] An apparatus 900 for maintaining voice call continuity provided in an embodiment of the present application can also execute the method of FIG4 and realize the functions of the apparatus 900 for maintaining voice call continuity in the embodiment shown in FIG4 , which will not be described in detail in this embodiment of the present application.

[0172] FIG10 is a schematic diagram of a structure of an apparatus 1000 for maintaining voice call continuity according to an embodiment of the present application. The apparatus 1000 can be applied to an MME. Referring to FIG10 , in a software implementation, the apparatus 1000 for maintaining voice call continuity can include: a number allocation module 1001 .

[0173] The number allocation module 1001 is used to allocate a first STN-SR session change number to the terminal after receiving a request from the terminal to register with the IP Multimedia Subsystem IMS domain and confirming that the home network of the terminal supports the Single Radio Voice Call Continuity SRVCC function.

[0174] Among them, the first STN-SR is different from the preset STN-SR. The first STN-SR is used to prohibit the terminal from registering in the circuit switched CS domain through the mobile management entity MME when the terminal registers in the IMS domain. The preset STN-SR is used to allow the terminal to register in the CS domain through the MME when the terminal cancels the IMS domain.

[0175] An apparatus 1000 for maintaining voice call continuity provided in an embodiment of the present application can also execute the method of FIG5 and realize the functions of the apparatus 1000 for maintaining voice call continuity in the embodiment shown in FIG5 , which will not be described in detail in this embodiment of the present application.

[0176] In short, the above description is only a preferred embodiment of the present application and is not intended to limit the scope of protection of the present application. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present application shall be included in the scope of protection of the present application.

[0177] The systems, devices, modules, or units described in the above embodiments may be implemented by computer chips or entities, or by products having certain functions. A typical implementation device is a computer. Specifically, the computer may be, for example, a personal computer, a laptop computer, a cellular phone, a camera phone, a smartphone, a personal digital assistant, a media player, a navigation device, an email device, a game console, a tablet computer, a wearable device, or a combination of any of these devices.

[0178] Computer-readable media includes permanent and non-permanent, removable and non-removable media that can be implemented by any method or technology to store information. The information can be computer-readable instructions, data structures, program modules or other data. Examples of computer storage media include, but are not limited to, phase change memory (PRAM), static random access memory (SRAM), dynamic random access memory (DRAM), other types of random access memory (RAM), read-only memory (ROM), electrically erasable programmable read-only memory (EEPROM), flash memory or other memory technology, compact disc read-only memory (CD-ROM), digital versatile disc (DVD) or other optical storage, magnetic cassettes, magnetic tape, magnetic disk storage or other magnetic storage devices or any other non-transmission media that can be used to store information that can be accessed by a computing device. As defined herein, computer-readable media does not include transitory computer-readable media (transitory media), such as modulated data signals and carrier waves.

[0179] It should also be noted that the terms "comprises," "includes," or any other variations thereof are intended to encompass non-exclusive inclusion, such that a process, method, commodity, or apparatus that includes a series of elements includes not only those elements but also other elements not explicitly listed, or includes elements inherent to such process, method, commodity, or apparatus. In the absence of further limitations, an element defined by the phrase "comprises a ..." does not exclude the presence of other identical elements in the process, method, commodity, or apparatus that includes the element.

[0180] The various embodiments in this application are described in a progressive manner. Similar parts between the various embodiments can be referred to in conjunction with each other. Each embodiment focuses on the differences from other embodiments. In particular, the system embodiment is generally similar to the method embodiment, so the description is relatively simple. For relevant parts, refer to the partial description of the method embodiment.

Claims

1. A method for maintaining voice call continuity, performed by a mobility management entity MME, the method comprising: If the terminal has not deregistered from the IP Multimedia Subsystem IMS domain, prohibiting the terminal from registering in the circuit switched CS domain; After the terminal deregisters the IMS domain, the terminal is allowed to register the CS domain.

2. The method according to claim 1, wherein when the terminal has not deregistered the IMS domain, prohibiting the terminal from registering the CS domain comprises: In the process of registering the IMS domain of the terminal, receiving a first session switching number STN-SR issued by a first device, wherein the first device includes an evolved packet core network EPC or a home user server HSS, the first STN-SR is different from the preset STN-SR, and the first STN-SR is allocated to the terminal by an access transfer control function ATCF or a service centralization and continuity application server SCC AS; When it is confirmed that the first STN-SR is different from a preset STN-SR, the terminal is prohibited from registering the CS domain.

3. The method according to claim 1 or 2, wherein the prohibiting the terminal from registering the CS domain comprises: By closing the SGs interface between the MME and the mobile service switching center MSC, the terminal is prohibited from registering the CS domain.

4. The method according to claim 2, wherein after the terminal deregisters the IMS domain, allowing the terminal to register the CS domain comprises: Receiving a second STN-SR issued by the first device after successfully responding to the IMS domain deregistration request of the terminal, wherein the second STN-SR is the same as the preset STN-SR; In a case where it is confirmed that the second STN-SR is the same as the preset STN-SR, the terminal is allowed to register the CS domain.

5. The method according to claim 1 or 4, wherein allowing the terminal to register a CS domain comprises: By opening the SGs interface between the MME and the mobile service switching center MSC, the terminal is allowed to register in the CS domain.

6. A method for maintaining voice call continuity, performed by a first device, wherein the first device includes an evolved packet core network EPC or a home subscriber server HSS, the method comprising: In the process of registering the IP multimedia subsystem IMS domain of the terminal, the session switching number STN-SR stored in itself is updated to a first STN-SR, and the first STN-SR is sent to the mobile management entity MME, wherein the first STN-SR is different from the preset STN-SR, and the first STN-SR is allocated to the terminal by the access transfer control function ATCF or the service centralization and continuity application server SCC AS, and the MME is used to prohibit the terminal from registering the circuit switching CS domain when confirming that the first STN-SR is different from the preset STN-SR; After successfully responding to the IMS domain deregistration request of the terminal, the STN-SR stored in itself is reset to the second STN-SR, and the second STN-SR is sent to the MME, wherein the second STN-SR is the same as the preset STN-SR, and the MME is used to allow the terminal to register the CS domain when confirming that the second STN-SR is the same as the preset STN-SR.

7. The method according to claim 6, Disabling the terminal from registering in the CS domain by closing the SGs interface between the MME and the mobile service switching center MSC; By opening the SGs interface, the terminal is allowed to register with the CS domain.

8. The method according to claim 6, wherein in the process of the terminal registering the IMS domain, updating the STN-SR stored in itself to the first STN-SR comprises: In the process of registering the terminal to the IMS domain, receiving the first STN-SR reported by the SCC AS, wherein the first STN-SR is reported by the SCC AS when confirming that the STN-SR currently stored in the first device is different from the first STN-SR; Update the STN-SR stored in itself to the first STN-SR.

9. The method according to claim 6, before resetting the STN-SR stored in itself to the second STN-SR, the method further comprises: Receiving an IMS domain deregistration request of the terminal sent by a call session control function CSCF; In a case where the server allocation type SAT carried in the IMS domain deregistration request is a deregistration type and the switch is turned on, a successful response to the IMS domain deregistration request is returned to the CSCF.

10. The method according to any one of claims 6 to 9, further comprising: A location update request of the terminal in the CS domain initiated by a mobile service switching center MSC is received, and the location of the terminal in the CS domain is updated, wherein the location update request is initiated after the MSC receives a location update trigger notification sent by the MME.

11. A method for maintaining voice call continuity, performed by a second device, wherein the second device includes an access transfer control function ATCF or a service centralization and continuity application server SCC AS, the method comprising: After receiving a request for a terminal to register with an IP Multimedia Subsystem IMS domain, if it is confirmed that the home network of the terminal supports the single radio voice call continuity SRVCC function, a first STN-SR session change number is allocated to the terminal, wherein the first STN-SR is different from the preset STN-SR, and the first STN-SR is used to prohibit the terminal from registering for a circuit switched CS domain through a mobile management entity MME when the terminal registers with the IMS domain, and the preset STN-SR is used to allow the terminal to register for the CS domain through MME when the terminal cancels the IMS domain.

12. A method for maintaining voice call continuity, comprising: After receiving the request of the terminal to register the IP multimedia subsystem IMS domain, if it is confirmed that the home network of the terminal supports the single wireless voice call continuity SRVCC function, the second device allocates a first session switching number STN-SR to the terminal, wherein the first STN-SR is different from the preset STN-SR, and the second device includes an access transfer control function ATCF or a service centralization and continuity application server SCC AS; During the process of terminal registration in the IMS domain, the first device receives the first STN-SR reported by the SCC AS, updates the STN-SR stored in the first device to the first STN-SR, and sends the first STN-SR to the mobility management entity MME, wherein the first device includes an evolved packet core network EPC or a home User server HSS; The MME prohibits the terminal from registering a circuit switched CS domain when confirming that the first STN-SR is different from a preset STN-SR; After successfully responding to the IMS domain deregistration request of the terminal, the first device resets the STN-SR stored in itself to the second STN-SR, and sends the second STN-SR to the MME; When confirming that the second STN-SR is the same as the preset STN-SR, the MME allows the terminal to register the CS domain.

13. A system for maintaining voice call continuity, comprising: A second device is used for allocating a first session switching number STN-SR to the terminal after receiving a request for registering an IP multimedia subsystem IMS domain by the terminal, if it is confirmed that the home network of the terminal supports a single wireless voice call continuity SRVCC function, wherein the first STN-SR is different from a preset STN-SR, and the second device includes an access transfer control function ATCF or a service centralization and continuity application server SCC AS; A first device, configured to receive the first STN-SR reported by the SCC AS during the process of registering the terminal to the IMS domain, update the STN-SR stored in itself to the first STN-SR, and send the first STN-SR to the mobile management entity MME; and, after successfully responding to the IMS domain deregistration request of the terminal, reset the STN-SR stored in itself to the second STN-SR, and send the second STN-SR to the MME, wherein the first device includes an evolved packet core network EPC or a home subscriber server HSS; The MME is used to prohibit the terminal from registering the CS domain when it is confirmed that the first STN-SR is different from the preset STN-SR, and allow the terminal to register the CS domain when it is confirmed that the second STN-SR is the same as the preset STN-SR.

14. An electronic device comprising: processor; a memory for storing instructions executable by the processor; The processor is configured to execute the instructions to implement the method as claimed in claims 1 to 11. Any of the methods described above. 15 . A computer-readable storage medium, when instructions in the storage medium are executed by a processor of an electronic device, the electronic device is enabled to execute the method according to claim 1 .

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