WO2009092245A1

WO2009092245A1 - Call originating method for multimedia session continuity service

Info

Publication number: WO2009092245A1
Application number: PCT/CN2008/073606
Authority: WO
Inventors: Zhendong Li; Zhenwu Hao
Original assignee: Zte Corporation
Priority date: 2008-01-08
Filing date: 2008-12-19
Publication date: 2009-07-30
Also published as: CN101692722B; CN101692722A

Abstract

The present invention provides a call originating method for multimedia session continuity service, and implements call originating in the multimedia session continuity and centralized control service of IP multimedia core network subsystem (IMS) domain. When multimedia session continuity service (MMSC) subscriber originates multimedia call including circuit switched domain speech, in the packet switched domain, the remote end called terminal number is taken as the called number, media session except speech is sent to MMSC application server; in the circuit switched domain, the number which can be identified by the MMSC application server istaken as the called number, speech call is originated to the MMSC application server; finally, the said MMSC application server combines the received media session of the said packet switched domain and speech session of the said circuit switched domain to one session, and the remote end called terminal number is taken as the called number to continue to make call. The application of the present invention can guarantee the MMSC application server to complete the session combination correctly and implement call originating correctly.

Description

Calling method for multimedia session continuity service

Technical field

The present invention relates to the field of communications, and more particularly to a method for implementing a call initiation in an IMS domain multimedia session continuity and centralized control service.

Background technique

IP (Internet Protocol, IP for short) Multimedia Subsystem (IMS) is an IP-based network proposed by the 3rd Generation Partnership Project (3GPP). The architecture, which builds an open and flexible business environment, supports multimedia applications and provides users with rich multimedia services.

IMS is an IP-based telecommunications network architecture, which is independent of the access technology. In addition to providing services for packet access networks such as GPRS (General Packet Radio Service) and WLAN (Wireless Local Area Network). It can also provide services for mobile worm networks such as GSM (Global System for Mobile communications) and UMTS (Universal Mobile Telecommunications System).

Mobile cellular networks such as GSM and UMTS use circuit switching technology, called Circuit Switched (CS) domain, to provide users with basic voice services and supplementary services based on voice services. When the CS domain accesses the IMS, it evolves into an access mode, and the service is completely provided by the IMS. This technology is called IMS Centralized Service (ICS).

At the same time, the user equipment (UE) needs to maintain the continuity of the multimedia session in various access modes. At this time, the multimedia session of the user UE not only maintains continuity when switching between packet switching domains (PSs), but also maintains continuous switching between PS domain and CS domain, PS domain and PS domain + CS domain. Sex. The technology to ensure this continuity is called IMS Multimedia Session Continuity (MMSC). According to the prior art, when an MMSC subscription user initiates a multimedia service and uses CS domain voice, the CS domain voice must access the IMS using the ICS technology. Figure 1 shows how the MMSC user initiates a call when it has a CS domain capable network access. As can be seen from Figure 1, the multimedia session of the MMSC user is divided into two parts:

The voice session is accessed to the IMS via the ICS in the CS domain. First, the user terminal UE-A establishes a CS session call with the ICS node via the CS domain (step 105), initiates a call to the user terminal UE-B; and then the ICS node calls the session control function (Serving Call Session Control Function, S-CSCF for short) initiates a session initial protocol SIP call request (step 106), the request carries the number of the called terminal UE-B and the voice session; the S-CSCF performs service logic processing (step 107); the S-CSCF redirects The MMSC-AS (MMSC application server) sends a session initiation protocol SIP call request, where the request carries the number of the called terminal UE-B and voice session information (step 108);

Multimedia sessions other than voice are accessed into the IMS via the PS domain. First, the terminal UE-A initiates a session initial protocol SIP call request to the S-CSCF via the PS domain, where the request carries the number of the called terminal UE-B and the MMSC session information (step 101); the S-CSCF performs service logic processing ( Step 102); Then, the S-CSCF sends a session initiation protocol SIP call request to the MMSC-AS (MMSC application server), where the request carries the number of the called terminal UE-B and the MMSC session information (step 103); MMSC- The AS waits for a voice session from the CS domain after receiving the SIP call request (step 104).

The above two parts of the session, that is, the voice session and the multimedia session other than the voice session, are executed concurrently without prioritization. After both sessions reach the MMSC server (Application Server, AS), the MMSC AS acts as a Back to Back User Agent (B2BUA), merges the two parts of the session into one session (step 109), and then merges The subsequent session is sent to the S-CSCF via the SIP call request (step 110), and the S-CSCF continues to transmit to the remote called user UE-B (step 111).

However, in the current technology, the MMSC session information cannot be carried in the call request from the ICS, so that in FIG. 1, if the step 103 arrives before the step 108, that is, the multimedia session of the PS domain other than the voice precedes the voice session of the CS domain. Upon reaching the MMSC AS, the MMSC AS will wait for the session of the CS domain to arrive. However, if step 108 precedes step 103, the MMSC AS will not succeed. Continue to wait, but continue to call, so that the session merge function performed in step 109 will not be completed.

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If the user is a MMSC contract, it is also an ICS contract. The user UE accesses both the circuit switched CS domain and the packet switched PS domain, but its PS access is a low speed IP access and cannot provide voice services. The voice is still provided by the CS domain, and the remaining multimedia sessions are provided in the PS domain. At this time, in the multimedia originating call that the MMSC signing user initiates the CS domain voice, how to correctly complete the session merging becomes a problem to be solved. Summary of the invention

The technical problem to be solved by the present invention is to provide a method for calling a multimedia session continuity service, which ensures that the MMSC application server correctly completes the session merge and implements a correct call in the IMS domain multimedia session continuity and centralized control service.

The present invention provides a method for calling a multimedia session continuity service, including:

The multimedia session continuity service, that is, when the MMSC user initiates a multimedia call:

In the packet domain, sending the media session other than voice to the MMSC application server by using the remote called terminal number as the called number;

In the circuit domain, the number that can be recognized by the MMSC application server is the called number, and a voice call is initiated;

After receiving the media session of the packet domain and the voice session of the circuit domain, the MMSC application server combines the two sessions into one session, and continues the call with the remote called terminal number as the called number. .

further,

The two sessions that are merged are that the MMSC user initiates a call in parallel in the circuit domain and the packet domain.

further,

The specific steps of the MMSC user to initiate a call in the circuit domain include:

The MMSC user centralizes the voice session in the circuit domain through the IP multimedia subsystem That is, the ICS node initiates a call, and the called number uses the number that the MMSC application server can recognize;

After receiving the call, the ICS node sends a session initial protocol call request, and uses the number that the MMSC application server can recognize as the called number, and routes the session initial protocol call request to the home service call session control function, that is, the S-CSCF;

The S-CSCF performs business logic processing;

The S-CSCF sends the session initiation protocol call request to the MMSC application server, where the session initiation protocol call request carries the voice conference information.

further,

The specific steps of the MMSC user to initiate a call in the packet domain include:

The MMSC user initiates a call in a packet domain in a media session other than voice. The called number in the call request is the number of the remote called terminal and contains MMSC session information, and the call request is routed to the home service call session control. The function is S-CSCF;

The S-CSCF performs business logic processing;

According to the initial filtering criterion, that is, the iFC trigger, the S-CSCF sends the session initial protocol call request to the MMSC application server, where the call request carries the MMSC session information.

further,

The MMSC session information includes information for describing whether there are remaining session branches; if the media session of the packet domain first reaches the MMSC application server, and the MMSC session information describes the remaining session branches, the MMSC application server will be based on This information waits for a voice session in the circuit domain to merge the two sessions.

further,

And the MMSC application server merges the voice session and the media session according to the association between the circuit domain voice session and the media session association information of the packet domain.

further, The association information is a calling number, or a calling number and a number that the MMSC application server can recognize.

further,

The MMSC user sends a media session other than voice to the MMSC application server in the circuit domain through the IP multimedia subsystem centralized service, that is, the ICS node; wherein the ICS node is an Il-cs architecture, or an Il-ps architecture. Or enhanced MSC architecture.

further,

The number that the MMSC application server can identify is statically configured in the user terminal, or dynamically obtained by the terminal during the registration process or in a previous session.

Further, the number that the MMSC application server can identify refers to the number of the MMSC application server, or the number that the MMSC application server can identify by other network elements.

Compared with the prior art, when the MMSC subscription user initiates a multimedia originating call including the CS domain voice, the two-part session is respectively sent, that is, the session A initiated by the PS domain, the session is the same as the prior art, the called number It is the remote called subscriber number and carries the MMSC information. In the CS domain, the ICS-initiated session B is changed to the number that the home IMS domain MMSC AS can recognize, such as the number of the MMSC AS. When the two calls arrive at the MMSC AS, the MMSC AS completes the session merge and continues the connection process.

The analysis shows that when session A arrives at the MMSC AS first, because it carries the MMSC session information, the MMSC AS will wait for the arrival of the session B; if the session B first arrives at the MMSC AS, because the called number is the number that the MMSC AS can recognize, the MMSC The AS knows that this session is part of the entire MMSC session and needs to wait for other parts of the MMSC session to arrive.

Therefore, the technical solution of the present invention can implement the correct combination of the two sessions by the MMSC AS, regardless of whether the session of the CS domain or the PS domain arrives first, so that the call can be correctly initiated. BRIEF abstract

1 is a schematic flowchart of a call initiated by an existing MMSC user;

2 is a schematic flowchart of implementing a call initiated by an MMSC user in the present invention; 3 is a schematic diagram of the first implementation manner of the Il-cs calling flow process of the present invention;

4 is a schematic diagram of the second implementation manner of the Il-cs calling process of the present invention;

Figure 5 is a schematic illustration of the Il-ps originating flow of the present invention;

Figure 6 is an enhanced MSC originating procedure of the present invention. Preferred embodiment of the invention

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention will be further described in detail with reference to the accompanying drawings.

The core idea of the present invention is: When an MMSC subscription user initiates a multimedia originating call including a CS domain voice, it separately transmits a two-part session, that is, a media session A initiated by the PS domain other than the voice session, and the session is the same as the prior art. The called number is the remote called subscriber number; in the CS domain, the ICS-initiated voice session B is changed to the number that the home IMS domain MMSC AS can recognize, such as the number of the MMSC AS. When the two calls arrive at the MMSC AS, the MMSC AS completes the session merge and continues the connection process.

When session A arrives at the MMSC AS first, because it carries information about the remaining session branches,

The MMSC AS will wait for the arrival of Session B; if Session B first arrives at the MMSC AS, the MMSC AS knows that the session is part of the entire MMSC session based on the number that the called MMSC AS can recognize, and needs to wait for other parts of the MMSC session to arrive.

When the MMSC AS receives sessions A and B, the MMSC AS acts as a back-to-back proxy B2BUA, merging the two sessions into one session and continuing to initiate a call to the destination.

As shown in FIG. 2, the process for implementing the MMSC user call initiation according to the present invention includes the following steps:

The MMSC user UE-A initiates a multimedia call, in which the media session other than voice initiates a call in the PS domain, and the UE-A sends a SIP call request, and the called number in the call request is the number of the remote called UE-B. And including MMSC session information, the call request is routed to a Serving Call Session Control Function (S-CSCF).

202) the S-CSCF performs business logic processing;

203) The S-CSCF sends a SIP call request to the MMSC AS according to an initial filter criterion (iFC). The call request carries the number of the remote called UE-B And MMSC session information.

The iFC filtering criterion is a triggering method of the standard IMS service, and the S-CSCf learns to forward the request to the MMSC AS by using the iFC.

The MMSC session information typically includes information describing whether there are remaining session branches, such as describing voice in a CS domain call.

204) The MMSC user UE-A initiates a multimedia call, in which the voice part initiates a call in the CS domain through the ICS technology, and the called number uses the number that the MMSC AS can recognize, such as the number of the MMSC AS. The number that the MMSC AS can identify may be statically configured in the user terminal, or may be dynamically obtained during the registration process or in a previous session.

205) After receiving the call, the ICS node sends a SIP call request, where the called number is MMSC

The number that the AS can identify, the SIP call request is routed to the home S-CSCF.

206) The S-CSCF performs business logic processing.

207. The S-CSCF sends a SIP call request to the MMSC AS according to an initial filter criterion (iFC). The SIP call request carries the voice session information and the number that the called MMSC AS can recognize.

208) The MMSC AS associates the received two sessions (ie, the voice session and the media session except the voice) and performs the combining process, and uses the number of the called terminal UE-B received in step 203 as the called number. Continuing to send a SIP call request, the SIP call request message carrying the merged session is first sent to the S-CSCF;

The MMSC AS associates the two sessions according to the received association information of the two session calls. The association information may be a calling number, or a calling number, and a number that the MMSC AS can identify, such as an MMSC. AS number and so on. When the session is associated, the calling number can be used as the association information. That is, the MMSC AS can determine that the calling number of the two sessions is the same calling party number, so that the two are the calls initiated by the same MMSC user. Combine 2 parts of the session. In the case where the calling number cannot be uniquely associated only, the associated information may be the calling number and the number that the MMSC application server can recognize.

209) The S-CSCF then routes the SIP call request to the remote called UE-B (the intermediate step is omitted). Wherein, steps 201-203 and steps 204-207 are parallel, without prioritization. Initiate call The called UE-A sends the voice session and the media session other than the voice to the MMSC-AS in parallel, and the MMSC-AS combines the two sessions into one session and then sends it out.

Since the ICS has three architectures, namely, an Il-cs architecture, an Il-ps architecture, and an enhanced MSC architecture, the following three embodiments of the ICS are combined with the implementation flow shown in FIG. 2, and the technical solutions of the present invention are indicated under each specific architecture. Implementation process. Among them, the user is signed by MMSC and also signed by ICS. The user UE accesses both the circuit switched CS domain and the packet switched PS domain, but its PS access is low-speed IP access, and cannot provide voice services. The voice is still provided by the CS domain, and the remaining multimedia sessions are provided in the PS domain. In the example, the multimedia originating call including the CS domain voice is initiated by the MMSC subscription user.

Example 1

3 is an implementation of the ICS in the Il-cs architecture of the present invention. The background is that the user terminal MMSC UE that subscribes to the MMSC accesses the IMS in the CS domain is Il-cs, and its multimedia component is carried in the PS domain. The specific steps of the MMSC UE preparing to initiate the multimedia call including the CS domain voice include: 301) The MMSC user UE sends the voice session information through the Unstructured Supplementary Service Data (USSD) on the ICS session control path, which is The calling number is a number that the MMSC AS can identify, such as the number of the MMSC AS, and the USSD message is first sent to the VMSC;

302) The VMSC forwards the received USSD message to the home ICCF, and the network element involved in the forwarding path is not related to the patent, and is not described herein;

303) The MMSC user UE sends a call setup message to the VMSC in the CS domain, and the target address of the message is the ICCF number;

After receiving the call setup message, the VMSC sends an ISUP initial address message carrying the ICCF address to the MGCF according to the called number;

305) The MGCF sends a SIP session request to the ICCF, where the called number is an ICCF number, and the message is first sent to the CSCF;

306) triggered by the iFC, the CSCF sends the received SIP call request to the ICCF;

307) The ICCF associates the messages of steps 302 and 306 after receiving the messages. ICCF issued Sending a SIP call request, whose target address is the number that the MMSC AS can recognize in step 302, such as the number of the MMSC AS, and the SIP request is first sent to the CSCF; here, the associated information is the calling number, or the ICCF. Number, here further merge the two messages after the association;

308) The iCF triggers, and the CSCF sends the received SIP call request to the MMSC AS. 309) The MMSC user UE sends a SIP call request to the destination in the PS domain, the destination address is the UE2 number, and the MMSC session information is included. First sent to the CSCF;

After receiving the step 309 message, the CSCF triggers the iFC to trigger the CSCF to send the received SIP call request to the MMSC AS.

311) After receiving the messages of steps 308 and 310, the MMSC AS associates with the session information to know that this is an MMSC call. The MMSC AS merges the received two sessions and acts as a B2BUA to continue to initiate a session to the destination UE2. The SIP session request is first sent to the CSCF. Here, the associated information is the calling number, or the calling number and the MMSC AS. A number that can be identified. The two sessions are further combined here and merged.

312) The CSCF routes the SIP call request to the destination address, where the process path is omitted. The steps 301, 303, and 309 are in parallel, and there is no order limitation. The call setup process after step 312 is known in the prior art, and is not described here.

Example 2:

4 is an implementation 2 of the ICS architecture of the present invention. The background is that the MMSC user UE accesses the IMS in the CS domain in the manner of Il-cs, and the multimedia component is carried in the PS domain. The MMSC user UE prepares to initiate a multimedia call including CS domain voice, and the ICCF address on the ICS bearer control path in the call is dynamically obtained. The specific steps are as follows:

401) The MMSC user UE sends the voice conference information through the USSD on the ICS session control path, and the called number is a number that the MMSC AS can identify, such as the number of the MMSC AS, and the USSD message is first sent to the VMSC;

The VMSC forwards the received USSD message to the home ICCF, and the network element involved in the forwarding path has nothing to do with the innovation of the present invention, and is not described here;

403) After receiving the message of step 402, the ICCF saves the voice session information in the USSD message. Such as the number that the MMSC AS can identify, and assign an IMS Routing Number (IMRN) in the E.164 format;

404) The ICCF returns the allocated IMRN to the MMSC user UE through the USSD message, where the network element passing through the path is not related to this patent and is ignored.

405) After receiving the IMRN, the MMSC user UE sends a call setup message to the VMSC in the CS domain, and the target address of the message is the received IMRN number;

406) after receiving the call setup message, the VMSC sends an ISUP initial address message to the MGCF according to the called number;

407) The MGCF sends a SIP session request to the ICCF, where the called number is IMRN, and the message is first sent to the CSCF;

408) by the iFC trigger, the CSCF sends the received SIP call request to the ICCF;

409) After receiving the message of step 408, the ICCF associates with the information stored in step 403 according to IMRN. The ICCF continues to send a SIP call request, and its target address is the number that the MMSC AS can recognize in step 402, and the SIP request is first sent to the CSCF;

410) The iCF triggers, and the CSCF sends the received SIP call request to the MMSC AS;

411) The MMSC user UE sends a SIP call request to the destination in the PS domain, the destination address is the UE2 number, and includes the MMSC session information, and the message is first sent to the CSCF;

412) After receiving the message of step 411, the CSCF triggers through the iFC, and the CSCF sends the received SIP call request to the MMSC AS.

413) After receiving the messages of steps 410 and 412, the MMSC AS associates with the session information to know that this is an MMSC call. The MMSC AS merges the received two sessions and acts as a B2BUA to continue to initiate a session to the destination UE2. The SIP session request is first sent to the CSCF. Here, the associated information is the calling number, or the calling number and the MMSC AS. A number that can be identified. The two messages are further merged here after association.

414) The CSCF SIP call request is routed to the destination address, where the process path is omitted. It should be noted that steps 401 to 410 are serial, and steps 401 and 411 are parallel. Or step 405 and step 411 are in parallel. The call setup process after step 414 is a prior art, and details are not described herein again.

Example 3:

FIG. 5 is an implementation of the ICS in the Il-ps architecture of the present invention. The background is that the mode in which the MMSC user UE accesses the IMS in the CS domain is Il-ps, and the multimedia component thereof is carried in the PS domain. MMSC User The specific steps for the UE to prepare to initiate a multimedia call containing CS domain voice are:

501) The MMSC user UE sends a SIP session request to the called UE2 on the ICS session control path, that is, the PS domain. The called number is a number that the MMSC AS can recognize, such as the number of the MMSC AS. Since the purpose of the request is to establish an ICS call control path, the call request does not contain SDP information. The message is first sent to the CSCF;

502) triggered by the iFC, the CSCF sends the received SIP call request to the ICCF;

503) The MMSC user UE sends a call setup message to the VMSC in the CS domain, and the target address of the message is the ICCF number;

504) after receiving the call setup message, the VMSC sends an ISUP initial address message to the MGCF according to the called number;

505) The MGCF sends a SIP session request to the ICCF, where the called number is an ICCF number, and the message is first sent to the CSCF;

506) triggered by the iFC, the CSCF sends the received SIP call request to the ICCF;

507) The ICCF associates the messages of steps 502 and 506 after receiving the messages. The ICCF continues to send a SIP call request, the target address is the number that the MMSC AS can recognize in step 502, such as the number of the MMSC AS, and the SIP request is first sent to the CSCF;

508) triggering by the iFC, the CSCF sends the received SIP call request to the MMSC AS;

509) the MMSC user UE sends a SIP call request to the destination in the PS domain, the destination address is the UE2 number, and includes the MMSC session information and the PS domain multimedia session SDP information, and the message is first sent to the CSCF;

510) After receiving the message of step 509, the CSCF triggers through the iFC, and the CSCF will receive the SIP. The call request is sent to the MMSC AS;

511) After receiving the messages of steps 508 and 510, the MMSC AS associates with the session information to know that this is an MMSC call. The MMSC AS merges the received two sessions and acts as a B2BUA, and continues to initiate a session to the destination UE2, and the SIP session request is first sent to the CSCF;

512) The CSCF routes the SIP call request to the destination address, where the process path is omitted. It should be noted that the steps 501, 503, and 509 are in parallel, and there is no order limitation. The call establishment process after step 512 is known in the prior art, and details are not described herein again.

Example 4:

FIG. 6 is an implementation of an enhanced MSC according to the present invention. The background is that the MMSC user UE accesses the IMS in the CS domain by enhancing the MSC, and the multimedia component thereof is carried in the PS domain. MMSC User The specific steps for the UE to prepare to initiate a multimedia call containing CS domain voice are:

601) The MMSC user UE sends a call setup message to the enhanced MSC in the CS domain, where the target address of the message is a number that the MMSC AS can identify, such as the number of the MMSC AS;

602) The enhanced MSC sends a SIP call request after receiving the call setup message, where the called number is a number that the MMSC AS can identify, and the message is first sent to the CSCF;

603) The iCF triggers, and the CSCF sends the received SIP call request to the MMSC AS.

604) the MMSC user UE sends a SIP call request to the destination in the PS domain, the destination address is the UE2 number, and contains the MMSC session information, and the message is first sent to the CSCF;

605) After receiving the message 604, the CSCF triggers the iFC, and the CSCF sends the received SIP call request to the MMSC AS.

606) After receiving the messages of steps 603 and 605, the MMSC AS associates with the session information to know that this is an MMSC call. The MMSC AS merges the received two sessions and acts as a B2BUA to continue to initiate a session to the destination UE2. The SIP session request is first sent to the CSCF. Here, the associated information is the calling number, or the calling number and the MMSC AS. A number that can be identified. The two messages are further merged here after association.

607) The CSCF routes the SIP call request to the destination address, where the process path is omitted. It should be noted that the steps 601 and 604 are in parallel, and there is no order limitation. The call establishment process after step 607 is available in the prior art and is not repeated.

In the foregoing embodiment, the number that the MMSC AS can identify may be the number of the MMSC AS, or may be the number assigned by the other network element that the MMSC AS can identify.

The "MMSC session information" in the above embodiment only mentions information for describing whether there are any remaining session branches, and may of course include other MMSC session content information such as a calling number, a called number, and a service type.

Similarly, the meaning of "voice session information" may also include the calling number, the number that the called MMSC application server can recognize, and the type of service.

The present invention has been described in terms of a preferred embodiment of the present invention, and is not intended to limit the invention, and various modifications and changes can be made by those skilled in the art. Therefore, any modifications, equivalent substitutions, improvements, and improvements made within the spirit and scope of the present invention are intended to be included within the scope of the present invention.

Industrial applicability

Compared with the prior art, when the MMSC subscription user initiates a multimedia originating call including the CS domain voice, the two-part session is respectively sent, that is, the session A initiated by the PS domain, the session is the same as the prior art, the called number It is the remote called subscriber number; in the CS domain, the ICS-initiated session B is changed to the number that the home IMS domain MMSC AS can recognize, such as the number of the MMSC AS. When the two calls arrive at the MMSC AS, the MMSC AS completes the session merge and continues the processing.

The analysis shows that when session A arrives at the MMSC AS first, because it carries the information of the remaining session branches, the MMSC AS will wait for the arrival of session B; if session B first arrives at the MMSC AS, it can be identified by the MMSC AS according to the called number. The number, MMSC AS knows that this session is part of the entire MMSC session and needs to wait for the other parts of the MMSC session to arrive.

Therefore, the technical solution of the present invention can implement the correct combination of the two sessions by the MMSC AS, regardless of whether the session of the CS domain or the PS domain arrives first, so that the call can be correctly initiated.

Claims

Claim

A calling method for a multimedia session continuity service, comprising: a multimedia session continuity service, that is, when an MMSC user initiates a multimedia call:

In the packet domain, the media session other than voice is sent to the MMSC application server by using the remote called terminal number as the called number;

In the circuit domain, the number that can be identified by the MMSC application server is the called number, and a voice call is initiated;

2. The calling method according to claim 1, wherein

3. The calling method according to claim 1, wherein the specific steps of the MMSC user initiating a call in the circuit domain include:

The MMSC user initiates a call in the circuit domain through the IP multimedia subsystem centralized service, that is, the ICS node, and the called number uses the number that the MMSC application server can recognize; after the ICS node receives the call, the session is initiated. The protocol call request, the number that can be identified by the MMSC application server is used as the called number, and the session initial protocol call request is routed to the home service call session control function, that is, the S-CSCF;

The S-CSCF performs business logic processing;

The S-CSCF sends the session initial protocol call request to the MMSC application server according to the initial filtering criterion, that is, the iFC trigger, and the session initial protocol call request carries the voice session information.

4. The calling method according to claim 1, wherein the specific steps of the MMSC user initiating a call in the packet domain include:

The MMSC user initiates a call in a packet domain by a media session other than voice, the call request The called number is the number of the remote called terminal and contains the MMSC session information, and the call request is routed to the home service call session control function, ie, the S-CSCF;

The S-CSCF performs business logic processing;

The S-CSCF sends a session initiation protocol call request to the MMSC application server according to the initial filtering criterion, that is, the iFC trigger, and the call request carries the MMSC session information.

5. The calling method according to claim 4, characterized in that

6. The calling method according to claim 1, wherein:

And the MMSC application server merges the voice session and the media session according to the association between the circuit domain voice session and the media session of the packet domain.

7. The calling method according to claim 6, wherein:

The associated information is a calling number, or a calling number and a number that the MMSC application server can recognize.

8. The calling method according to claim 1 or 3, characterized in that

9. The calling method according to claim 1 or 3 or 6, wherein

The number that the MMSC application server can recognize is statically configured in the user terminal, or dynamically obtained by the terminal during registration or in a previous session.

The calling method according to claim 1 or 3 or 6, wherein the number that the MMSC application server can identify refers to the number of the MMSC application server, or the MMSC application server allocated by other network elements can identify Number.