CN109688610B

CN109688610B - Method, device, equipment and storage medium for switching single-standby voice continuous service

Info

Publication number: CN109688610B
Application number: CN201710971069.2A
Authority: CN
Inventors: 费树明; 崔立军; 傅友; 于雯辉; 杨溢
Original assignee: China Mobile Communications Group Co Ltd; China Mobile Group Chongqing Co Ltd
Current assignee: China Mobile Communications Group Co Ltd; China Mobile Group Chongqing Co Ltd
Priority date: 2017-10-18
Filing date: 2017-10-18
Publication date: 2021-06-08
Anticipated expiration: 2037-10-18
Also published as: CN109688610A

Abstract

The embodiment of the invention discloses a switching method, a device, equipment and a storage medium of a single-standby voice continuous service, which are used for improving the switching success rate of an SRVCC service, avoiding network resource waste caused by the switching failure of the SRVCC service and improving network performance indexes. The method comprises the following steps: receiving a switching request message sent by a base station, wherein the switching request message carries an identifier of user equipment requesting to perform SRVCC service switching; acquiring the session state of the user equipment in an internet protocol multimedia subsystem (IMS) domain according to the switching request message; if the session state of the user equipment is determined to be the state before ringing, suspending the switching request message until the session state of the user equipment is determined to be switched from the state before ringing to the state before ringing, and continuing to perform SRVCC switching according to the switching request message; or, if the session state of the user equipment is determined to be the deletion state, terminating the SRVCC handover.

Description

Method, device, equipment and storage medium for switching single-standby voice continuous service

Technical Field

The present invention belongs to the field of communication technology, and in particular, to a method, an apparatus, a device and a storage medium for switching a single-standby voice continuous service.

Background

The Single Radio Voice Call Continuity (SRVCC) service refers to that when a Voice over LTE (VoLTE) User roams from an Evolved Universal Terrestrial Radio Access Network (E-UTRAN) to a Terrestrial Radio Access Network (UMTS Terrestrial Radio Access Network, UTRAN)/Radio Access Network (GSM EDGE Radio Access Network, GERAN) during a Call, the User Equipment (User Equipment, UE) and the Network Equipment are handed over, and the Call of the User is maintained without interruption.

As shown in fig. 1, the handover procedure of SRVCC can be divided into the following steps:

step one, after an eNodeB (evolved node b) determines that an access network needs to be switched, an eNodeB sends a handover request message to a Mobility Management Entity (MME) in a source EPC domain 101.

Step two, the MME separates the voice bearer whose class Identifier (QCI) is equal to 1 from other bearers according to the SRVCC indication carried in the handover request message, and selects an interconnection Function (SRVCC IWF) in the CS domain 102 according to the target Identifier in the handover request message, and initiates a packet switched domain handover to circuit switched domain request (PS to CS) request message to the SRVCC IWF through the Sv interface. The PS to CS request message carries a STN-SR (session Transfer) number allocated to the UE by a C-MSISDN (mobile station international subscriber identity) and an Access Transfer Control Function (ATCF).

Step three, after the SRVCC IWF in the CS domain 102 receives the PS to CS request message, finds a target Mobile Service Switch Center (MSC) server (i.e., an MSC server to which the handover target side belongs) according to the target identifier carried in the PS to CS request message, and then executes a handover procedure between the SRVCC IWF and the target MSC server.

Step four, after the bearing establishment of the target side UTRAN/GERAN network is completed, the SRVCC IWF establishes the bearing of SRVCC IWF and ATCF in the IMS domain 103 according to the STN-SR number.

Step five, the ATCF updates the bearing information on the Access Transfer Gateway (ATGW) according to the session to be switched of the C-MSISDN correlation user equipment, switches the local terminal media plane to the bearing of the UTRAN/GERAN network, and informs a Service centralized and continuous Application Server (SCC AS) to update the Access domain information of the UE.

In the existing SRVCC procedure, after receiving a handover request message sent by an eNodeB, an MME immediately sends an SRVCC handover request PS to CS request message to a corresponding SRVCC IWF, without considering what state a current internet protocol Multimedia subsystem IMS (IP Multimedia System) session is in. Therefore, even if the session is currently in the following special state, the MME will still initiate the SRVCC procedure as usual: 1. in the session establishment process before the ringing of the called party; 2. the session has started to release the procedure (e.g. normal on-hook, early release of the calling party, or delayed release of the called party), but the IMS-specific bearer has not been deleted by the EPC (Evolved Packet Core) domain.

1. For the SRVCC procedure (i.e. bSRVCC) before session ringing, it needs all the support of multiple network elements such AS UE, eNodeB, SRVCC IWF, ATCF, SCC AS, etc., and the procedure is very complex, and also needs MME, SAE-GW (SGW and PGW, serving gateway and packet data gateway) to correctly process the relevant procedures for bearer modification/deletion. Therefore, the probability of failure of the bSRVCC procedure is high.

2. For the SRVCC procedure initiated during the disconnection process of the call, the IMS domain will delete the session very quickly, and therefore will eventually reject the IST (session transfer) request sent by the SRVCC IWF, and the SRVCC procedure will also fail.

It is obvious that the existing SRVCC procedure is prone to the occurrence of low-success-rate bSRVCC, invalid SRVCC, etc. (a large number of bSRVCC handover failures and SRVCC handover failures caused by disconnection of a call actually exist in the existing network), which wastes network resources, reduces network performance indexes, and fails to improve the service perception of the VoLTE user. In contrast, the handover under ringing (aSRVCC) and the handover under talking have high success rate.

Disclosure of Invention

The embodiment of the invention provides a switching method, a device, equipment and a storage medium of a single-standby voice continuous service, which are used for improving the switching success rate of an SRVCC service, avoiding network resource waste caused by the switching failure of the SRVCC service and improving network performance indexes.

In a first aspect, an embodiment of the present invention provides a method for switching a single standby voice continuous SRVCC service, where the method includes:

receiving a switching request message sent by a base station, wherein the switching request message carries an identifier of user equipment requesting to perform SRVCC service switching;

acquiring the session state of the user equipment in an internet protocol multimedia subsystem (IMS) domain according to the switching request message;

if the session state of the user equipment is determined to be the state before ringing, suspending the switching request message until the session state of the user equipment is determined to be switched from the state before ringing to the state before ringing, and continuing to perform SRVCC switching according to the switching request message; or, if the session state of the user equipment is determined to be the deletion state, terminating the SRVCC handover.

In a possible embodiment, acquiring the session state of the ue in the IMS domain according to the handover request message includes:

sending a session state request message to a service centralization and continuous application server SCC AS through a home subscriber server HSS, wherein the session state request message is used for requesting the session state of the user equipment in an IMS domain;

and receiving a session state response message returned by the SCC AS through the HSS, wherein the session state response message carries the session state of the user equipment in an IMS domain.

In a possible embodiment, determining that the session state of the user equipment is switched from the pre-ringing state to the ringing state includes:

sending a session state subscription request message to a service centralization and continuous application server SCC AS through a home subscriber server HSS;

receiving a session state notification message returned by the SCC AS through the HSS;

and determining that the session state of the user equipment is switched from a pre-ringing state to a ringing state according to the indication information carried in the session state notification message.

In a possible implementation manner, the session state notification message is generated and sent by the SCC AS immediately after receiving the 180 ringing message.

In a possible embodiment, sending a session state request message to a service centralization and continuity application server SCC AS by a home subscriber server HSS includes:

and sending the session state request message to the HSS through an S6a interface, and sending the session state request message to the SCC AS through an Sh interface by the HSS.

In a second aspect, an embodiment of the present invention provides a device for switching a single standby voice continuous SRVCC service, where the device includes:

a receiving module, configured to receive a handover request message sent by a base station, where the handover request message carries an identifier of a user equipment requesting to perform SRVCC service handover;

an obtaining module, configured to obtain, according to the handover request message, a session state of the ue in an IMS domain;

a processing module, configured to suspend the handover request message if it is determined that the session state of the ue is a pre-ringing state, until it is determined that the session state of the ue is switched from the pre-ringing state to the ringing state, and continue to perform SRVCC handover according to the handover request message; or, if the session state of the user equipment is determined to be the deletion state, terminating the SRVCC handover.

In a third aspect, an embodiment of the present invention provides a network-side device, where the network-side device includes a processor, a memory, and a communication component, where the communication component sends and/or receives data under the control of the processor, a preset program is stored in the memory, and the processor reads the program in the memory and executes the following processes according to the program:

receiving a switching request message sent by a base station through the communication assembly, wherein the switching request message carries an identifier of user equipment requesting to perform SRVCC service switching;

In a possible embodiment, the processor is specifically configured to:

indicating the communication component to send a session state request message to a service centralization and continuous application server SCC AS through a home subscriber server HSS, wherein the session state request message is used for requesting the session state of the user equipment in an IMS domain;

and receiving a session state response message returned by the SCC AS through the HSS through the communication assembly, wherein the session state response message carries the session state of the user equipment in an IMS domain.

In a possible embodiment, the processor is specifically configured to:

instructing the communication component to send a session state subscription request message to a service centralization and continuous application server SCC AS through a home subscriber server HSS;

instructing the communication component to receive a session state notification message returned by the SCC AS through the HSS;

In a possible embodiment, the processor is specifically configured to:

instructing the communication component to send the session state request message to the HSS over an S6a interface, the HSS sending the session state request message to the SCC AS over an Sh interface.

In a possible implementation manner, the network side device is a mobility management entity MME.

In a fourth aspect, an embodiment of the present invention provides a storage medium, where a computer program is stored, and the computer program is used for executing, after being loaded by a processor, the method described in the first aspect according to the computer program.

Based on the above technical solution, in the embodiment of the present invention, after receiving a handover request message for an SRVCC service of a user equipment, a session state of the user equipment in an IMS domain is acquired, and when it is determined that the session state of the user equipment is a pre-ringing state, execution of SRVCC service handover is stopped until it is determined that the session state of the user equipment is switched to the ringing state, and SRVCC service handover is continuously executed, thereby avoiding a handover failure caused by SRVCC service handover when the user equipment is in the pre-ringing state. And, under the condition that the session state of the user equipment is determined to be the deletion state, the SRVCC service switching is directly terminated, thereby avoiding resource waste caused by unnecessary SRVCC service switching. In conclusion, different SRVCC service switching processes are performed according to the session state of the IMS domain of the user equipment, thereby ensuring the smooth operation of the SRVCC service switching process, improving the success rate of SRVCC service switching, avoiding the waste of network resources, and improving the network performance index and the service perception of the user.

Drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required to be used in the embodiments of the present invention will be briefly described below, and for those skilled in the art, other drawings can be obtained according to the drawings without creative efforts.

Fig. 1 illustrates a schematic diagram of SRVCC service handover procedure in the prior art;

fig. 2 is a flow chart illustrating SRVCC service handover in an embodiment of the present invention;

fig. 3 is a schematic diagram illustrating an overall flow of SRVCC service handover in an embodiment of the present invention;

fig. 4 shows a signaling flow diagram of SRVCC service handover in an embodiment of the present invention;

fig. 5 is a schematic structural diagram illustrating a switching apparatus of an SRVCC service according to an embodiment of the present invention;

fig. 6 shows a schematic structural diagram of a network-side device in an embodiment of the present invention.

Detailed Description

Features and exemplary embodiments of various aspects of the present invention will be described in detail below, and in order to make objects, technical solutions and advantages of the present invention more apparent, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not to be construed as limiting the invention. It will be apparent to one skilled in the art that the present invention may be practiced without some of these specific details. The following description of the embodiments is merely intended to provide a better understanding of the present invention by illustrating examples of the present invention.

It should be noted that, in this document, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising … …" does not exclude the presence of other identical elements in a process, method, article, or apparatus that comprises the element.

In order to improve the success rate of switching the SRVCC service, avoid the waste of network resources caused by the failure of switching the SRVCC service, and improve the network performance index, the embodiment of the present invention provides a method for switching the SRVCC service, the core idea of the method is: before initiating the SRVCC service switching process, the session state of the user equipment in the IMS domain is obtained, and the SRVCC service switching is determined according to the session state.

In the embodiment of the present invention, the SRVCC service handover procedure may be specifically executed by a core network device, such as an MME, and in the following embodiment, only the MME is taken as an execution subject for example, and the possibility that other core network devices are taken as execution subjects is not excluded in the application.

The specific implementation process of SRVCC service handover is shown in fig. 2, and is described in detail as follows:

step 201: receiving a Handover request (Handover Required) message sent by a base station, wherein the Handover request message carries an identifier of a user equipment requesting to perform SRVCC service Handover.

Specifically, after determining that SRVCC service handover needs to be performed for the user equipment according to a system measurement report reported by the user equipment, a base station (eNodeB) generates a handover request message for the user equipment, and the handover request message carries an identifier of the user equipment. The base station sends the switching request message to the MME.

Step 202: and acquiring the session state of the user equipment in the IMS domain according to the switching request message.

In a specific embodiment, a specific process of acquiring a session state of a user equipment in an IMS domain is as follows: sending a session state request message to an SCC AS through an HSS, wherein the session state request message is used for requesting the session state of user equipment in an IMS domain; and receiving a session state response message returned by the SCC AS through the HSS, wherein the session state response message carries the session state of the user equipment in the IMS domain.

Specifically, the session state request message is sent to the HSS through the S6a interface, and is sent by the HSS to the SCC AS through the Sh interface.

For example, the MME sends a session status request message to the HSS through the S6a interface according to the identity of the user equipment (such as IMSI (international mobile subscriber identity), MSISDN (mobile station international subscriber identity), etc. of the user equipment, which is carried in the handover request message; the HSS sends a session state request message to the SCC AS through the Sh interface according to the identity of the user equipment (e.g., an IMPI (IP multimedia private identity), an IMPU (IP multimedia public identity), etc. of the user equipment); SCC AS inquires the current session state (before ringing, during conversation, deleting, etc.) of the user equipment, and returns a session state response message to HSS, wherein the session state response message carries the indication information of the current session state of the user equipment; HSS returns the session state response message to MME; the MME acquires the indication information of the current session state of the user equipment from the session state response message, and determines the current session state of the user equipment according to the indication information.

Step 203: if the session state of the user equipment is determined to be the state before ringing, suspending the switching request message until the session state of the user equipment is determined to be switched from the state before ringing to the state before ringing, and continuing to perform SRVCC service switching according to the switching request message; or, if the session state of the user equipment is determined to be the deletion state, terminating the SRVCC service switching.

In the embodiment of the present invention, an MME adopts different processing manners for a handover request message of an SRVCC service according to different obtained session states of a user equipment, which is specifically as follows:

if the MME determines that the session state of the user equipment is 'deleting', directly sending a switching preparation failure message to the base station, and terminating the SRVCC service switching process so as to avoid resource waste caused by unnecessary SRVCC service switching;

if the MME determines that the session state of the user equipment is in ringing or in conversation, switching is carried out according to a normal SRVCC service switching flow, namely a PS to CS switching request is directly initiated to an SRVCC IWF;

and if the MME determines that the session state of the user equipment is before ringing, suspending the SRVCC service switching process temporarily until the session state of the user equipment is switched from the before-ringing state to the ringing state, and continuing to switch the SRVCC service according to the switching request message, thereby avoiding the switching failure caused by switching the SRVCC service under the condition that the user equipment is in the before-ringing state.

In a specific embodiment, a specific implementation manner of the MME determining that the session state of the user equipment is switched from the pre-ringing state to the ringing state is as follows: sending a session state subscription request message to an SCC AS through an HSS; receiving a session state notification message returned by the SCC AS through the HSS; and determining that the session state of the user equipment is switched from the state before ringing to the ringing state according to the indication information carried in the session state notification message. Specifically, the session state notification message is generated by the SCC AS immediately after receiving the 180 ringing message and returned through the HSS.

A more detailed description of the SRVCC service handover procedure will be provided below by a specific embodiment, fig. 3 is a schematic diagram illustrating a complete flow of the SRVCC service handover, and fig. 4 is a schematic diagram illustrating a signaling flow of the SRVCC service handover.

As shown in fig. 3 and 4, the detailed procedure of SRVCC service handover is as follows:

step 301: after deciding to switch the SRVCC service according to the system measurement report reported by the UE, the base station sends a switching request message to the MME;

step 302: the MME sends a session state request message to the HSS through an S6a interface according to the identity (IMSI, MSISDN, etc.) of the UE carried in the handover request message;

step 303: HSS sends the session state request message to SCC AS through Sh interface according to UE ID (IMPI, IMPU, etc.);

step 304: SCC AS inquires the current session state of UE (before ringing, during conversation, deleting, etc.), and returns a session state response message to HSS, wherein the session state response message carries the indication information of the current session state of UE;

step 305: HSS returns the session state response message to MME;

the MME performs different processing on the SRVCC service switching process according to the difference of the session state indicated in the session state response message:

a, if the MME determines that the session state is 'deleting', executing step 306, directly sending a handover preparation failure message to the base station, and terminating the SRVCC service handover process;

b, if the MME determines that the session state is "ringing" or "in call", then step 307 is executed, namely, a normal SRVCC service switching process is executed, and a PS to CS switching request is directly initiated to an SRVCC IWF;

c, if the MME determines that the session state is "before ringing", then step 308 to step 314 are executed, which is specifically as follows:

step 308: the MME temporarily suspends the SRVCC service flow;

step 309: MME initiates a session state subscription request message to HSS;

step 310: HSS forwards the session state subscription request message to SCC AS;

step 311: SCC AS receives 180 ringing messages replied by the called side;

step 312: SCC AS returns a session state notification message to HSS, wherein the session state notification message carries indication information for indicating that the session state of UE is switched from a pre-ringing state to a ringing state;

step 313: HSS sends the session state notification message to MME;

step 314: and the MME determines that the session state of the UE is switched to a ringing state from a state before ringing according to the indication information carried in the session state notification message, directly initiates a PS to CS switching request to the SRVCC IWF, and continues the subsequent SRVCC service switching process.

Based on the above technical solution, in the embodiment of the present invention, after receiving a handover request message for an SRVCC service of a user equipment, an MME acquires a session state of the user equipment in an IMS domain, and stops performing SRVCC service handover until it is determined that the session state of the user equipment is switched to a ring state, and continues to perform SRVCC service handover, thereby avoiding a handover failure caused by performing SRVCC service handover when the user equipment is in the ring state. And, under the condition that the session state of the user equipment is determined to be the deletion state, the SRVCC service switching is directly terminated, thereby avoiding resource waste caused by unnecessary SRVCC service switching. In conclusion, different SRVCC service switching processes are performed according to the session state of the IMS domain of the user equipment, thereby ensuring the smooth operation of the SRVCC service switching process, improving the success rate of SRVCC service switching, avoiding the waste of network resources, and improving the network performance index and the service perception of the user.

In summary, in the embodiment of the present invention, the MME is allowed to obtain the IMS session state, and when the session is found to be in a special state, the success rate of session handover before ringing is increased by a manner of delaying handover, or an invalid handover request is avoided by a manner of terminating handover, so that the service awareness of the VoLTE user is limited and improved.

Based on the same inventive concept, an embodiment of the present invention further provides a device for switching an SRVCC service, where specific implementation of the device may refer to description of the method embodiment, and repeated details are not repeated, as shown in fig. 5, the device mainly includes:

a receiving module 501, configured to receive a handover request message sent by a base station, where the handover request message carries an identifier of a user equipment requesting to perform SRVCC service handover;

an obtaining module 502, configured to obtain, according to the handover request message, a session state of the ue in an IMS domain;

a processing module 503, configured to suspend the handover request message if it is determined that the session state of the ue is the pre-ringing state, until it is determined that the session state of the ue is switched from the pre-ringing state to the ringing state, and continue to perform SRVCC handover according to the handover request message; or, if the session state of the user equipment is determined to be the deletion state, terminating the SRVCC handover.

Based on the same inventive concept, an embodiment of the present invention further provides a network-side device, where specific implementation of the network-side device may refer to description of the method embodiment, and repeated parts are not repeated, as shown in fig. 6, the network-side device mainly includes a processor 601, a memory 602, and a communication component 603, where the communication component 603 sends and/or receives data under the control of the processor 601, a preset program is stored in the memory 602, and the processor 601 reads the program in the memory 602 and executes the following processes according to the program:

receiving a handover request message sent by a base station through a communication component 603, wherein the handover request message carries an identifier of a user equipment requesting to perform SRVCC service handover;

acquiring the session state of the user equipment in the IMS domain according to the switching request message;

if the session state of the user equipment is determined to be the state before ringing, suspending the switching request message until the session state of the user equipment is determined to be switched from the state before ringing to the state before ringing, and continuing to perform SRVCC switching according to the switching request message; or if the session state of the user equipment is determined to be the deletion state, terminating the SRVCC handover.

In one embodiment, the processor 601 is specifically configured to:

instructing the communication component 603 to send a session status request message to the SCC AS via the HSS, the session status request message being used to request a session status of the user equipment in the IMS domain;

a session state response message returned by the SCC AS via the HSS is received by the communication component 603, where the session state response message carries a session state of the user equipment in the IMS domain.

In one embodiment, the processor 601 is specifically configured to:

instruct the communication component 603 to send a session state subscription request message to the SCC AS via the HSS;

instructing the communication component 603 to receive a session state notification message returned by the SCC AS via the HSS;

and determining that the session state of the user equipment is switched from the state before ringing to the ringing state according to the indication information carried in the session state notification message.

In one embodiment, the processor 601 is specifically configured to:

the communication component 603 is instructed to send a session state request message to the HSS over the S6a interface, which is sent by the HSS to the SCC AS over the Sh interface.

In a specific embodiment, the network side device is an MME.

In particular implementations, the communication components, memory, and processors are connected in a bus that may include any number of interconnected buses and bridges that link together various circuits including one or more processors represented by processors, memory represented by memory, and communication components represented by communication components. The bus may also link various other circuits such as peripherals, voltage regulators, power management circuits, and the like, which are well known in the art, and therefore, will not be described any further herein.

The processor is responsible for managing the bus and general processing and may also provide various functions including timing, peripheral interfaces, voltage regulation, power management, and other control functions. And the memory may be used to store data used by the processor in performing operations. The communication component receives or transmits data under the control of the processor.

Alternatively, the processor may be a CPU (central processing unit), an Application Specific Integrated Circuit (ASIC), a Field Programmable Gate Array (FPGA), or a Complex Programmable Logic Device (PLD).

It is to be understood that the invention is not limited to the specific arrangements and instrumentality described above and shown in the drawings. A detailed description of known methods is omitted herein for the sake of brevity. In the above embodiments, several specific steps are described and shown as examples. However, the method processes of the present invention are not limited to the specific steps described and illustrated, and those skilled in the art can make various changes, modifications and additions or change the order between the steps after comprehending the spirit of the present invention.

The functional blocks shown in the above-described structural block diagrams may be implemented as hardware, software, firmware, or a combination thereof. When implemented in hardware, it may be, for example, an electronic circuit, an Application Specific Integrated Circuit (ASIC), suitable firmware, plug-in, function card, or the like. When implemented in software, the elements of the invention are the programs or code segments used to perform the required tasks. The program or code segments may be stored in a machine-readable medium or transmitted by a data signal carried in a carrier wave over a transmission medium or a communication link. A "machine-readable medium" may include any medium that can store or transfer information. Examples of a machine-readable medium include electronic circuits, semiconductor memory devices, ROM, flash memory, Erasable ROM (EROM), floppy disks, CD-ROMs, optical disks, hard disks, fiber optic media, Radio Frequency (RF) links, and so forth. The code segments may be downloaded via computer networks such as the internet, intranet, etc.

It should also be noted that the exemplary embodiments mentioned in this patent describe some methods or systems based on a series of steps or devices. However, the present invention is not limited to the order of the above-described steps, that is, the steps may be performed in the order mentioned in the embodiments, may be performed in an order different from the order in the embodiments, or may be performed simultaneously.

As described above, only the specific embodiments of the present invention are provided, and it can be clearly understood by those skilled in the art that, for convenience and brevity of description, the specific working processes of the system, the module and the unit described above may refer to the corresponding processes in the foregoing method embodiments, and are not described herein again. It should be understood that the scope of the present invention is not limited thereto, and any person skilled in the art can easily conceive various equivalent modifications or substitutions within the technical scope of the present invention, and these modifications or substitutions should be covered within the scope of the present invention.

Claims

1. A method for switching a single standby voice continuous SRVCC service is characterized in that the method comprises the following steps:

2. The method for switching SRVCC service according to claim 1, wherein obtaining the session status of the ue in the IMS domain according to the handover request message comprises:

3. The method for switching SRVCC service according to claim 1 or 2, wherein determining that the session state of the user equipment is switched from a pre-ringing state to a ringing state comprises:

4. The method of claim 3, wherein the session state notification message is generated and sent by the SCC AS immediately after receiving a 180 ringing message.

5. The method for switching SRVCC service according to claim 2, wherein the sending the session status request message to the service centralization and continuity application server SCC AS through the home subscriber server HSS comprises:

6. A handover apparatus for a single standby voice continuous SRVCC service, the apparatus comprising:

7. The network side equipment is characterized by comprising a processor, a memory and a communication component, wherein the communication component sends and/or receives data under the control of the processor, a preset program is stored in the memory, and the processor reads the program in the memory and executes the following processes according to the program:

8. The network-side device of claim 7, wherein the processor is specifically configured to:

9. The network-side device of claim 7 or 8, wherein the processor is specifically configured to:

10. The network-side device of claim 8, wherein the processor is specifically configured to:

11. The network side device according to claim 7, wherein the network side device is a mobility management entity MME.

12. A storage medium, characterized in that the storage medium has stored therein a computer program for executing the method of any of claims 1 to 5 in accordance with the computer program after being loaded by a processor.