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

Abstract

The embodiment of the invention provides a method for keeping voice call continuity, electronic equipment and a computer readable storage medium, and the method comprises the steps: prohibiting a terminal from registering a circuit switching (CS) domain under the condition that the terminal does not log out an IP multimedia subsystem (IMS) domain; and after the terminal cancels the IMS domain, allowing the terminal to register the CS domain. Therefore, the voice call continuity can be maintained, the CS domain resources occupied by the IMS domain user are reduced, the 2G network exit is effectively promoted, the occupation of the 2G network resources is reduced, and the 2G network resources are saved.

Description

Technical Field

[0001] The present invention 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

[0002] Currently, after a Voice over Long-Term Evolution (VoLTE) user accesses a 4G network, he or she will register on both the 4G network and the 2G network, so that the user can maintain the continuity of voice call services when moving between the 4G network and the 2G network.

[0003] In this situation where VoLTE users are online on both the 2G network and the 4G network at the same time, although the continuity of voice call services can be maintained, there is also a waste of network resources, which needs to be improved. Summary of the invention

[0004] 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.

[0005] To solve the above technical problems, the embodiments of the present application are implemented as follows:

[0006] In a first aspect, a method for maintaining voice call continuity is provided, which is performed by a mobility management entity MME, and the method includes:

[0007] If the terminal has not deregistered from the IP Multimedia Subsystem IMS domain, prohibiting the terminal from registering in the circuit switched CS domain;

[0008] After the terminal deregisters the IMS domain, the terminal is allowed to register the CS domain.

[0009] In a second aspect, a method for maintaining voice call continuity is provided, which is performed by a first device, where the first device includes an evolved packet core network EPC or a home subscriber server HSS, and the method includes:

[0010] 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;

[0011] 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.

[0012] In a third aspect, a method for maintaining voice call continuity is provided, which is performed by a second device, where the second device includes an access transfer control function ATCF or a service centralization and continuity application server SCC AS, and the method includes:

[0013] 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.

[0014] In a fourth aspect, a method for maintaining voice call continuity is provided, comprising:

[0015] 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;

[0016] The first device receives the first STN-SR reported by the SCC AS during the process of the terminal registering the IMS domain, 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 subscriber server HSS;

[0017] 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;

[0018] 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;

[0019] 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.

[0020] In a fifth aspect, a system for maintaining voice call continuity is provided, including:

[0021] 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;

[0022] 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;

[0023] 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.

[0024] In a sixth aspect, an electronic device is provided, including:

[0025] processor;

[0026] a memory for storing instructions executable by the processor;

[0027] The processor is configured to execute the instructions to implement the method as described in the first aspect.

[0028] In a seventh aspect, a computer-readable storage medium is provided. When the instructions in the storage medium are executed by a processor of an electronic device, the electronic device can execute the method as described in any one of the first aspect, the second aspect and the third aspect.

[0029] In the embodiment of the present application, if the terminal has not deregistered the IP Multimedia Subsystem IMS domain, the terminal can be prohibited from registering the circuit switched CS domain; after the terminal deregisters the IMS domain, the terminal is allowed to register 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 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. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0031] Figure 1 It is the voice routing process of 2G and 4G online at the same time in the related technology.

[0032] Figure 2 This is the voice routing process for 2G and 4G simultaneously online provided in the embodiment of the present application.

[0033] Figure 3 It is a flowchart of a method for maintaining voice call continuity provided by an embodiment of the present application.

[0034] Figure 4 It is a flowchart of a method for maintaining voice call continuity provided by another embodiment of the present application.

[0035] Figure 5 It is a flowchart of a method for maintaining voice call continuity provided by another embodiment of the present application.

[0036] Figure 6 It is a flowchart of a method for maintaining voice call continuity provided by another embodiment of the present application.

[0037] Figure 7 It is a schematic diagram of the structure of an electronic device according to an embodiment of the present application.

[0038] Figure 8 It is a structural diagram of a device for maintaining voice call continuity provided by an embodiment of the present application.

[0039] Fig. 9 It is a structural diagram of a device for maintaining voice call continuity provided by another embodiment of the present application.

[0040] Fig.10 It is a structural diagram of a device for maintaining voice call continuity provided by another embodiment of the present application. DETAILED DESCRIPTION

[0041] In order to enable those skilled in the art to better understand the technical solutions in the embodiments of the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in one or more embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in the field without creative work should fall within the scope of protection of this document.

[0042] The terms "first", "second", etc. in the present application and the claims are used to distinguish similar objects, and are not used to describe a specific order or sequence. It should be understood that the data used in this way can be interchangeable under appropriate circumstances, so that the present application embodiment can be implemented in an order other than those illustrated or described here. In addition, the term "and / or" in the present application and the claims represents at least one of the connected objects, and the character " / " generally represents that the objects associated with each other before and after are a kind of "or" relationship.

[0043] 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.

[0044] The second generation mobile communication technology (2G) is a cellular mobile communication technology. User equipment (UE) mainly accesses the 2G network through the wireless air interface and obtains services. The UE exchanges information with the base station through the air interface and accesses the core network through wireless. In the 2G network, the UE is also called a mobile station (MS, MobileStation).

[0045] The Mobile Switching Center (MSC) is used to provide call control, mobility management, authentication and encryption functions in the Circuit Switched (CS) domain.

[0046] 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.

[0047] 3GPP (3rd Generation Partnership Project) has been developing the LTE (Long Term Evolution) mobile communication system since R8. In LTE, UE accesses the 4G network through the wireless air interface and obtains services. The UE exchanges information with the base station through the air interface and exchanges information with the mobility management entity of the core network through NAS (non-Access Stratum) signaling.

[0048] EPC (Evolved Packet Core) is the evolved packet core network and the core network of 4G LTE.

[0049] The Mobile Management Entity (MME) is a core network control plane entity, responsible for user authentication, authorization and contract checking, user mobility management, packet data network (PDN) connection and bearer maintenance, and triggering paging in user IDLE state.

[0050] The Home Subscription Server (HSS) stores the user's subscription information, including authentication, services, etc.

[0051] According to the definition of 3GPP, 4G system has realized the support of IP Multimedia Core Network Subsystem (IMS), through which IP-based multimedia sessions, including voice, video and other multimedia services, can be realized. The main functional entities in the IMS system include: Proxy callsession controlFunction (P-CSCF), Interrogating callsession controlFunction (I-CSCF), Serving call session controlFunction (S-CSCF), Access Transfer ControlFunction (ATCF), and Application Server (AS).

[0052] In the early stage of LTE network construction or when LTE network coverage is insufficient, when a user is using the LTE network for voice calls and moves to an area where the LTE signal is weak but the 2G wireless signal coverage is good, in order to ensure the voice call continuity (VCC) of the long-term evolution network voice service (Voice Over LTE, VoLTE), the 3GPP organization proposed a VoLTE voice service continuity solution SRVCC, that is, when the UE moves between the LTE network and the 2G network, the IMS controls the smooth switching between VoIP voice and CS domain voice. Figure 1 It is a schematic diagram of the voice routing process when 2G and 4G are online at the same time in the related technology.

[0053] 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):

[0054] Service Call Continuity Application Server (SCC AS).

[0055] Session Initiation Protocol (SIP) is developed by the Internet Engineering Task Force (IETF) for multi-party multimedia communications. According to the definition of IETF RFC2543, SIP is a text-based application layer control protocol, independent of the underlying transport protocol TCP / UDP / SCTP, used to establish, modify and terminate two-party or multi-party multimedia sessions on IP networks.

[0056] Single Radio Voice Call Continuity (SRVCC)

[0057] Session Transfer Number for SRVCC (STN-SR).

[0058] Combine the following Figure 1 , the voice routing process of 2G and 4G online at the same time in the related technology is explained.

[0059] like Figure 1 As shown in the figure, the voice routing process when 2G and 4G are online at the same time may include (briefly described below):

[0060] (I)EPC attachment process:

[0061] Step 101: MME sends an Update Location Request (ULR) message to EPC.

[0062] Generally speaking, the ULR carries the International Mobile Subscriber Identity (IMSI) of the UE and the SRVCC capability of the UE.

[0063] Step 102: When confirming that the UE supports SRVCC, the EPC returns a location update response (Update Location Answer, ULA) to the MME. The ULA carries the STN-SR determined according to the user's subscription.

[0064] Specifically, when the UE initiates the EPC attachment process, the UE will indicate whether it supports SRVCC in the MS Network Capability parameter in the Attach Request message sent. After receiving the UE's attachment request, the MME confirms whether the UE supports SRVCC. If so, the above step 101 is executed.

[0065] (II) IMS Domain Registration

[0066] Step 103, when the UE registers in the IMS domain (SIP register) through ATCF, if the home network of the UE supports using ATCF to enhance the SRVCC function, the ATCF allocates a STN-SR according to the operator's policy and sends it to the SCC AS through a SIP message.

[0067] Optionally, if the ATCF does not allocate the STN-SR, the SCC AS allocates the STN-SR.

[0068] 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.

[0069] 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.

[0070] 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.

[0071] Step 107: HSS notifies EPC to update STN-SR through an internal message.

[0072] Step 108: EPC (or HSS) notifies MME to update STN-SR via IDR (Insert-Subscriber-Data-Request) message.

[0073] Step 109: MME feeds back a response to update STN-SR to EPC (or HSS) via an IDA (Insert-Subscriber-Data-Answer) message.

[0074] Step 110: The EPC notifies the HSS of a response to update the STN-SR through an internal message.

[0075] Step 111: The HSS feeds back a response of updating the STN-SR to the SCC AS via a Profile-Update-Answer (PUA) message.

[0076] 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.

[0077] (III) Originating and terminating call process when switching from 4G to 2G via SRVCC

[0078] Step 112: The MSC receives a handover request from the MME or SGSN through the Sv interface to handover the voice session from the IMS domain to the CS domain.

[0079] Step 113: The MSC sends a handover request message to the ATCF of the visited location through the Mw interface.

[0080] The ATCF of the visited location is determined based on the updated STN-SR, that is, the MSC routes the ATCF through the STN-SR number obtained from the MME or SGSN.

[0081] Step 114: ATCF sends an Invite message to the SCC AS to switch the voice session.

[0082] In steps 115 to 119, the SCC AS checks whether the UE has the 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.

[0083] 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 in step 117 carries the (Internal Message Ack) 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.

[0084] Among them, C-MSISDN refers to Combined MSISDN, which is a number used to identify mobile users in mobile communication networks. It consists of a country code (CC) and a mobile user number (MSISDN). C-MSISDN is usually used to support multiple services based on SIM cards, such as voice, SMS, data and other services, and to support mobile users to use the same number on different terminal devices. In some wireless communication standards, such as GSM, C-MSISDN is called Integrated Circuit Card Identifier (ICCID).

[0085] pass Figure 1 It is not difficult to find that in the relevant technology, 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 is online or not, the 2G resources are always occupied. Although this can ensure the high reliability of continuous voice calls, there is also a problem of resource waste.

[0086] In order to solve this problem, the embodiment of the present application proposes the technical concept of "prohibiting the terminal from registering the CS domain when the terminal has registered and has not deregistered the IMS domain, and allowing the terminal to register the CS domain after the terminal deregisters the IMS domain". Based on this technical concept, the embodiment of the present application proposes a voice routing solution for 2G and 4G simultaneously online, and its process is as follows: Figure 2 As shown, a brief introduction is given below.

[0087] like Figure 2 As shown, a 2G and 4G voice routing process provided in an embodiment of the present application when both are online simultaneously may include:

[0088] Step 201: The I-CSCF sends a User-Authorization-Request (UAR) message to the HSS to register with the IMS domain.

[0089] 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.

[0090] Step 202: The HSS returns a User-Authorization-Answer (UAA) carrying the S-CSCF address to the I-CSCF.

[0091] The S-CSCF address carried in the UAA is dynamic.

[0092] Step 203: The S-CSCF sends a Server-Assignment-Request (SAR) to the HSS to register the IMS domain and obtain the user subscription information.

[0093] Usually, the server assignment type (Server-Assignment-Type, SAT) carried in the SAR is a registration type, that is, SAT=registration.

[0094] Step 204: The HSS returns a Server-Assignment-Answer (SAA) to the S-CSCF, which carries the user subscription information.

[0095] 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.

[0096] 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).

[0097] 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.

[0098] Step 207, the SCC AS sends a Profile-Update-Request (PUR) message to the HSS according to the operator policy. The PUR carries the first STN-SR allocated by the ATCF or 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.

[0099] Step 208: The HSS feeds back a response of updating the STN-SR to the SCC AS via a Profile-Update-Answer (PUA) message.

[0100] 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.

[0101] When the MME confirms that the updated STN-SR is a non-preset STN-SR, the terminal is prohibited from registering the CS domain. Specifically, the SGs interface between the MME and the mobile service switching center MSC is closed to prohibit the terminal from registering the CS domain. This can make the terminal exit the 2G network when the IMS domain is attached, thereby saving 2G network resources.

[0102] Step 210: The MME feeds back a response to update the STN-SR to the EPC (or HSS) via an IDA (Insert-Subscriber-Data-Answer) message.

[0103] Step 211: When the user logs out in the IMS domain, the S-CSCF sends a SAR message to the HSS through the Cx interface to deregister in the IMS domain.

[0104] 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).

[0105] Among them, the deregistration class can be:

[0106] TIMEOUT_DEREGISTRATION,USER_DEREGISTRATION,ADMINISTRA TIVE_DEREGISTRATION,DEREGISTRATION_TOO_MUCH_DATA,TIMEOUT_DEREGISTRATION_STORE_SERVER_NAME,USER_DEREGISTRATION_STORE_SERVER_NAME,AUTHENTICATION_FAILURE,AUTHENTICATION_TIMEOUT

[0107] Step 213: The HSS sends the second STN-SR to the MME via an IDR message.

[0108] 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).

[0109] Step 215: The MME notifies the MSC / VLR to trigger location registration via the SGs interface.

[0110] 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.

[0111] from Figure 2 It can be seen that, through a 2G and 4G voice routing process provided by an embodiment of the present application, by inserting different STN-SRs to the MME, the terminal can be prohibited from registering the circuit switched CS domain when the terminal has not deregistered the IP multimedia subsystem IMS domain; after the terminal deregisters the IMS domain, the terminal is allowed to register 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 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.

[0112] It should be noted that Figure 2 The present invention focuses on describing a 2G and 4G simultaneous online voice routing process provided by an embodiment of the present application. Figure 3 The differences between the voice routing processes of 2G and 4G simultaneously online in the related art shown are as follows, thus omitting some existing steps.

[0113] Based on the above technical concept, the embodiment of the present application also proposes a method for maintaining voice call continuity, which is described below from the perspectives of different execution entities in conjunction with the accompanying drawings.

[0114] An embodiment of the present application provides a method for maintaining voice call continuity, which can be executed by an MME, such as Figure 3 As shown, the method may include:

[0115] Step 301: If the terminal has not deregistered from the IP Multimedia Subsystem IMS domain, prohibit the terminal from registering the Circuit Switching CS domain.

[0116] As an example, step 301 may specifically include: during the process of terminal registration in the IMS domain, receiving a first STN-SR issued by a first device, wherein the first device includes an EPC or an HSS, and the first STN-SR is different from a 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 in the CS domain.

[0117] Of course, it is also possible to determine whether to prohibit the terminal from registering 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 the CS domain after confirming that the terminal is registered in the IMS domain and the IMS domain is not cancelled.

[0118] Further, the prohibiting the terminal from registering the CS domain includes: prohibiting the terminal from registering the CS domain by closing the SGs interface between the MME and a mobile service switching center MSC.

[0119] Step 302: After the terminal deregisters the IMS domain, the terminal is allowed to register the CS domain.

[0120] 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; and upon confirming that the second STN-SR is the same as the preset STN-SR, allowing the terminal to register the CS domain.

[0121] Similarly, whether to allow the terminal to register the CS domain may not be determined by "determining whether the second STN-SR issued by the first device is the preset STN-SR", but directly allowing the terminal to register the CS domain after confirming that the terminal has deregistered the IMS domain.

[0122] Further, the allowing the terminal to register the CS domain may include: allowing the terminal to register the CS domain by opening an SGs interface between the MME and a mobile service switching center MSC.

[0123] Figure 3 The embodiment shown provides a voice routing process for 2G and 4G to be online at the same time. Since the terminal can be prohibited from registering the circuit switched CS domain when the terminal has not deregistered the IP multimedia subsystem IMS domain; after the terminal deregisters the IMS domain, the terminal is allowed to register the CS 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 withdrawal, reducing the occupation of 2G network resources, and saving 2G network resources.

[0124] Another embodiment of the present application provides a method for maintaining voice call continuity, which can be performed by a first device, wherein the first device includes an EPC or an HSS, such as Figure 4 As shown, the method may include:

[0125] Step 401: During the process of the terminal registering the IP Multimedia Subsystem IMS domain, the session switching number STN-SR stored in the terminal is updated to the first STN-SR, and the first STN-SR is sent to the mobility management entity MME.

[0126] 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. 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.

[0127] Specifically, the MME may prohibit the terminal from registering in the CS domain by closing the SGs interface between the MME and the MSC.

[0128] 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 when 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.

[0129] 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.

[0130] 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.

[0131] Specifically, the MME may enable the terminal to register the CS domain by opening the SGs interface.

[0132] Figure 4 The illustrated embodiment 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, the occupation of CS domain resources by IMS domain users can be reduced, effectively promoting 2G network withdrawal, reducing the occupation of 2G network resources, and saving 2G network resources.

[0133] Optionally, before resetting the STN-SR stored in itself to the second STN-SR, Figure 4 The method shown 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.

[0134] Optionally, Figure 4 The method shown may also include: receiving a location update request of 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 can be understood that the switching of SRVCC from 4G to 2G can be achieved through this step.

[0135] Another embodiment of the present application provides a method for maintaining voice call continuity, which can be performed by a second device, wherein the second device includes an ATCF or an SCC AS, such as Figure 4 As shown, the method may include:

[0136] Step 501: after receiving a request from a terminal to register 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 switching number is allocated to the terminal.

[0137] 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 the circuit switched CS domain through the mobile management entity MME when the terminal registers the IMS domain. The preset STN-SR is used to allow the terminal to register the CS domain through the MME when the terminal cancels the IMS domain.

[0138] Figure 5 The illustrated embodiment 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 when the terminal has not deregistered 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 withdrawal, reducing the occupation of 2G network resources, and saving 2G network resources.

[0139] like Figure 6 As shown, the embodiment of the present application also provides a method for maintaining voice call continuity, which may include:

[0140] Step 601: After receiving a request from a terminal to register an IP Multimedia Subsystem IMS domain, if the second device confirms that the home network of the terminal supports the Single Radio Voice Call Continuity SRVCC function, the second device allocates a first session switching number STN-SR to the terminal.

[0141] 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.

[0142] 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 the STN-SR stored in itself to the first STN-SR, and sends the first STN-SR to the mobility management entity MME.

[0143] The first device includes EPC or HSS.

[0144] 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 the circuit switched CS domain.

[0145] Step 604: 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;

[0146] 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.

[0147] In the embodiment of the present application, if the terminal has not deregistered the IP Multimedia Subsystem IMS domain, the terminal can be prohibited from registering the circuit switched CS domain; after the terminal deregisters the IMS domain, the terminal is allowed to register 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 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.

[0148] Corresponding to Figure 6 The method shown in the figure, the embodiment of the present application also provides a system for maintaining voice call continuity, including:

[0149] 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;

[0150] 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;

[0151] 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.

[0152] The system can obtain Figure 6 The same technical effects as those of the method shown will not be described in detail.

[0153] The above describes specific embodiments of the present application. Other embodiments are within the scope of the appended claims. In some cases, the actions or steps recorded in the claims can be performed in an order different from that in the embodiments and still achieve the desired results. In addition, the processes depicted in the accompanying drawings do not necessarily require the specific order or continuous order shown to achieve the desired results. In some embodiments, multitasking and parallel processing are also possible or may be advantageous.

[0154] Figure 7 This is a schematic diagram of the structure of an electronic device according to an embodiment of the present application. Figure 7 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. Of course, the electronic device may also include hardware required for other services.

[0155] The processor, network interface and memory can be interconnected through an internal bus, which can be an ISA (Industry Standard Architecture) bus, a PCI (Peripheral Component Interconnect) bus or an EISA (Extended Industry Standard Architecture) bus. The bus can be divided into an address bus, a data bus, a control bus, etc. For ease of representation, Figure 7 Only one bidirectional arrow is used in the diagram, but this does not mean that there is only one bus or only one type of bus.

[0156] The memory is used to store the program. Specifically, the program may include a program code, and the program code includes a computer operation instruction. The memory may include a memory and a non-volatile memory, and provides instructions and data to the processor.

[0157] The processor reads the corresponding computer program from the non-volatile memory into the memory and then runs it, forming a device for maintaining the continuity of the voice call at the logical level. The processor executes the program stored in the memory and is specifically used to perform the following operations:

[0158] If the terminal has not deregistered from the IP Multimedia Subsystem IMS domain, prohibiting the terminal from registering in the circuit switched CS domain;

[0159] After the terminal deregisters the IMS domain, the terminal is allowed to register the CS domain.

[0160] Alternatively, the processor executes the program stored in the memory and is specifically configured to perform the following operations:

[0161] 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;

[0162] 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.

[0163] Alternatively, the processor executes the program stored in the memory and is specifically configured to perform the following operations:

[0164] 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.

[0165] The above application Figure 7The method performed by the device for maintaining voice call continuity disclosed in the illustrated embodiment can be applied to a processor or implemented by a processor. The processor may be an integrated circuit chip with signal processing capabilities. In the implementation process, each step of the above method can be completed by an integrated logic circuit of hardware in the processor or an instruction in the form of software. The above 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 gates or transistor logic devices, 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 the processor can also be any conventional processor, etc. The steps of the method disclosed in the embodiments of the present application can be directly embodied as a hardware decoding processor for execution, or a combination of hardware and software modules in the decoding processor for execution. The software module can be located in a storage medium mature in the art such as a random access memory, a flash memory, a read-only memory, a programmable read-only memory, or an electrically erasable programmable memory, a register, etc. The storage medium is located in the memory, and the processor reads the information in the memory and completes the steps of the above method in combination with its hardware.

[0166] The electronic device may also perform Figure 3 , Figure 4 or Figure 5 A method and a device for maintaining voice call continuity are implemented in Figure 3 , Figure 4 or Figure 5 The functions in the illustrated embodiment will not be described in detail in the embodiments of the present application.

[0167] Of course, in addition to software implementation methods, the electronic device of the present 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.

[0168] The embodiment of the present application also provides a computer-readable storage medium, which stores one or more programs, wherein the one or more programs include instructions, which, when executed by a portable electronic device including a plurality of application programs, enable the portable electronic device to execute Figure 3 , Figure 4 or Figure 5 The method of the illustrated embodiment.

[0169] Figure 8 FIG. 8 is a schematic diagram of a structure of an apparatus 800 for maintaining voice call continuity provided by an embodiment of the present application. The apparatus 800 can be applied to MME. Figure 8 In a software implementation, the apparatus 800 for maintaining voice call continuity may include: a registration prohibiting module 801 and a registration allowing module 802 .

[0170] The registration prohibition module 801 is used to prohibit the terminal from registering in the circuit switching CS domain when the terminal has not deregistered from the IP Multimedia Subsystem IMS domain.

[0171] As an example, the registration prohibition module 801 can be specifically used to: during the process of terminal registration in the IMS domain, receive a first STN-SR issued by a first device, wherein the first device includes an EPC or an HSS, and the first STN-SR is different from a 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 in the CS domain.

[0172] Of course, the registration prohibition module 801 may not determine whether to prohibit the terminal from registering the CS domain by "determining whether the first STN-SR issued by the first device is the preset STN-SR", but directly prohibit the terminal from registering the CS domain after confirming that the terminal is registered in the IMS domain and the IMS domain is not cancelled.

[0173] 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 service switching center MSC.

[0174] The registration allowing module 802 is used to allow the terminal to register the CS domain after the terminal deregisters the IMS domain.

[0175] 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 when confirming that the second STN-SR is the same as the preset STN-SR, allow the terminal to register the CS domain.

[0176] 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.

[0177] Furthermore, the registration prohibition 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 a mobile service switching center MSC.

[0178] The device 800 for maintaining voice call continuity provided by the embodiment of the present application can also execute Figure 3 The method and the device 800 for maintaining the continuity of the voice call are implemented in Figure 3 The functions of the illustrated embodiment will not be described in detail in the embodiments of the present application.

[0179] Fig. 9 FIG. 9 is a schematic diagram of a structure of a device 900 for maintaining voice call continuity provided by an embodiment of the present application. The device 900 can be applied to MME. Fig. 9 In a software implementation, the device 900 for maintaining voice call continuity may include: a first sending module 901 and a second sending module 902.

[0180] The first sending module 901 is used to update the session switching number STN-SR stored in itself to the 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.

[0181] 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. 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.

[0182] Specifically, the MME may prohibit the terminal from registering in the CS domain by closing the SGs interface between the MME and the MSC.

[0183] 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.

[0184] The second sending module 902 is used to reset the STN-SR stored in itself to the second STN-SR after successfully responding to the IMS domain deregistration request of the terminal, and send the second STN-SR to the MME.

[0185] 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.

[0186] Specifically, the MME may enable the terminal to register the CS domain by opening the SGs interface.

[0187] The device 900 for maintaining voice call continuity provided by the embodiment of the present application can also execute Figure 4 The method and the device 900 for maintaining the continuity of the voice call are implemented in Figure 4 The functions of the illustrated embodiment will not be described in detail in the embodiments of the present application.

[0188] Fig.10 FIG. 1 is a schematic diagram of a structure of a device 1000 for maintaining voice call continuity provided by an embodiment of the present application. The device 1000 can be applied to MME. Fig.10 In a software implementation, the apparatus 1000 for maintaining voice call continuity may include: a number allocation module 1001.

[0189] The number allocation module 1001 is used to allocate a first STN-SR session change number to the terminal after receiving a request for registering the IP Multimedia Subsystem IMS domain by the terminal and confirming that the home network of the terminal supports the single radio voice call continuity SRVCC function.

[0190] 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 the circuit switched CS domain through the mobile management entity MME when the terminal registers the IMS domain. The preset STN-SR is used to allow the terminal to register the CS domain through the MME when the terminal cancels the IMS domain.

[0191] The device 1000 for maintaining voice call continuity provided by the embodiment of the present application can also execute Figure 5 The method and the device 1000 for maintaining the continuity of the voice call are implemented in Figure 5 The functions of the illustrated embodiment will not be described in detail in the embodiments of the present application.

[0192] In short, the above description is only a preferred embodiment of the present application and is not intended to limit the protection scope of the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

[0193] The systems, devices, modules or units described in the above embodiments may be implemented by computer chips or entities, or by products with 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 smart phone, 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.

[0194] Computer readable media include permanent and non-permanent, removable and non-removable media that can be implemented by any method or technology to store information. 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 disk read-only memory (CD-ROM), digital versatile disk (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 temporary computer readable media (transitory media), such as modulated data signals and carrier waves.

[0195] It should also be noted that the terms "include", "comprises" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, commodity or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, commodity or device. In the absence of more restrictions, the elements defined by the sentence "comprises a ..." do not exclude the existence of other identical elements in the process, method, commodity or device including the elements.

[0196] Each embodiment in this application is described in a progressive manner, and the same or similar parts between the embodiments can be referred to each other, and each embodiment focuses on the differences from other embodiments. In particular, for the system embodiment, since it is basically similar to the method embodiment, the description is relatively simple, and the relevant parts can be referred 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 by 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 SCCAS; 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 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 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; The first device receives the first STN-SR reported by the SCC AS during the process of the terminal registering the IMS domain, 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 subscriber 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 according to any one of claims 1 to 11. 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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