CN101232499B

CN101232499B - Method for implementing media surface switch in replacement function

Info

Publication number: CN101232499B
Application number: CN2007101250752A
Authority: CN
Inventors: 沈斌
Original assignee: ZTE Corp
Current assignee: ZTE Corp
Priority date: 2007-12-14
Filing date: 2007-12-14
Publication date: 2010-12-01
Anticipated expiration: 2027-12-14
Also published as: CN101232499A

Abstract

The invention discloses a method of realizing media switching in a replacement function, which is applied in the communication technical field. The method includes the following steps: a third-party user of an IP multimedia subsystem domain sends a call request for a new session two to a media gateway control network element for replacing the session one between a first user of a circuit-switched domain and a second user of the IP multimedia subsystem domain; according to the call request of the session two, the IP multimedia gateway control network element makes a bearing switch of the session two replacing the session one under the control of the media gateway control network element; the first user and the third user enter a steady session state of session two. By the method, the bearing switching of media channels among the first, the second and the third users by the interworking of the IP multimedia subsystem domain and the circuit-switched domain through the media gateway control network elements and the IP multimedia gateway control network elements.

Description

A kind of method that in replacing function, realizes the switching of medium face

Technical field

The present invention relates to a kind of medium face changing method of communication system, relate in particular to a kind of method that the medium face switches that in replacing function, realizes.

Background technology

IMS (IP Multimedia Core Network Subsystem, IP Multimedia System) is a kind of IP-based network framework that proposes by 3GPP, it has made up an opening and service environment flexibly, support multimedia application, and for the user provides abundant multimedia service, and widely-used Session Initiation Protocol carries out call signaling control in the IMS territory.

PSTN (Public Switched Telephone Network, public switched telephone network), ISDN (Integrated Services Digital Network, integrated services digital network) fixed telephone network such as, GSM (Global System for Mobile communication, global system for mobile communications), CDMA (Code Division Multiple Access, code division multiple access inserts), WCDMA, CDMA2000, TD-SCDMA (Time-Division Synchronization Code Division-Multiple-Access, Time Division-Synchronous Code Division Multiple Access) mobile telephone network such as circuit domain has then adopted traditional circuit-switched technology more, all these networks are referred to as CS (Circuit Switched, circuit switching) territory.The CS territory can provide voice, video and based on the data service of circuit domain for the user equally, and CS territory call signaling commonly used is ISUP (ISDN User Part, ISUP), BICC (Bearer Independent Call Control is with the calling control of bearer independent).

For realizing IMS territory and the intercommunication of CS territory, need dispose MGCF (MediaGateway Control Function MGCF) and IM-MGW (IPMultimedia-Media Gateway Function at IMS territory network boundary, IP multimedia gateway function) network element, be used for finishing and the CS territory between voice, data and multimedia call service intercommunication, interworking protocol sees ITU-T (International Telecommunication Union-Telecommunication for details, International Telecommunications Union-telecommunication standardization sector) Q.19 12.5 and 3GPP (3rd Generation Partnership Project, third generation partner program) TS 29.163.IMS territory and CS territory are by the MGCF/IM-MGW intercommunication, as shown in Figure 1; MGCF mainly finishes the conversion of IMS territory and CS territory call signaling, and IM-MGW mainly realizes the intercommunication of IMS territory and CS territory medium face, and MGCF is by H248 agreement control IM-MGW, thus separating of having realized that signaling control and medium control.

RFC 3891 is as RFC 3261 (Request For Comment 3261, request comment 3261) expansion, introduced Replaces (replacement) function in the IMS territory among the RFC 3891, this function can use a new session to replace the session of current existence, and can be used for realizing the multinomial business in the IMS territory, for example ECT (Explicit Communication Transfer, call display shift) and CONF (Conference, meeting) etc.

The basic principle of Replaces function, shown in Fig. 2 a, suppose that A, B, C are three users in the IMS territory, represent with IMS A, IMS B and IMS C respectively, and when having stable state or astable session 1 between A, B, then the realization flow of Replaces function comprises the steps:

Step 201, IMS C initiate new session INVITE (invitation) to IMS B; Wherein, INVITE comprises Replaces header (replacement head), is used to identify the session 1 of substitute I MS A and the current existence of IMS B;

After step 202, IMS B confirm that the Dialog (session) 1 that will replace exists, to IMS C loopback success message;

Step 203, IMS C successfully set up Dialog (session) 2 according to described response message between IMS B and IMS C, and send the session acknowledge message to IMS B;

Step 204, IMS B ask according to Replaces, finish the session 1 with IMS A;

Step 205, IMS A send to IMS B and discharge session 1 success message.

Wherein, Replaces header defines in RFC3891, and the session that its indication is known by this leader will be released and logically be substituted by the session that the INVITE that comprises it is created; Definition Replaces header is as follows among the RFC 3891:

Replaces＝″Replaces″HCOLON?callid*(SEMI?replaces-param)

replaces-param＝to-tag?/from-tag/early-flag/generic-param

to-tag＝″to-tag″EQUAL?token

from-tag＝″from-tag″EQUAL?token

early-flag＝″early-only″

Wherein, in RFC 3891 definition:

Callid: call identification, the parameter in the Session Initiation Protocol;

To-tag: purpose label, the parameter in the Session Initiation Protocol;

From-tag: source label, the parameter in the Session Initiation Protocol.

After the Replaces flow process took place, the original session 1 between IMS A, the IMS B was replaced by the new session between IMS B, the IMSC 2, and IMS B, IMS C enter talking state, and IMS A transfers the free time to, shown in Fig. 2 b and 2c.

In the existing standard, RFC3891 only is confined to the IMS territory to the discussion of Replaces function, and the discussion of 29.163 pairs of IMS territories of ITU-TQ.1912.5,3GPP TS and the intercommunication of CS territory does not relate to the Replaces function.In view of the extensive use scene of IMS territory and the intercommunication of CS territory, research has realistic meaning with the intercommunication occasion that the Replaces function in IMS territory expands to IMS territory and CS territory.

The Replaces function that 3GPP TS 24.147 V7.5.0 have related under IMS territory and the CS territory intercommunication situation is simply used, provided one by MGCF/IM-MGW invitation POTS (Plain OldTelephone Service, Plain Old Telephone Service) user is to the example flow of IMS territory meeting, see also accompanying drawing 3a, its realization flow comprises the steps:

Step 301, IMS user UE-A (User Equipment A, subscriber equipment A) call out and enter stable state by the calling 1 that MGCF is initiated to CS territory user; Wherein, a calling of setting up between UE-A and CS territory user, by a session of setting up between UE-A and MGCF, and composition is called out in a CS territory of setting up between MGCF and CS territory user, corresponding to the session 1 of calling out 1, MGCF has shielded the CS territory to UE-A, so for UE-A, calling 1 and session 1 need not to distinguish;

Step 302, UE-A send INVITE to the AS of IMS territory meeting (Application Server, application server), set up and be connected to a meeting 2;

Step 303, UE-A send REFER (transfer) request to AS; Wherein, comprise Replaces function relevant parameter, indication AS is initiated to CS territory user's calling, and this calls out the calling 1 that needs to replace UE-A and the current existence of CS territory user, promptly indicates AS to invite CS territory user to add meeting 2;

Step 304, AS send NOTIFY (notice) to UE-A, the progress of notice REFER request;

Step 305, AS be according to the indication of REFER, initiates newly to call out 3 to CS territory user by MGCF, comprises Replaces header in its INVITE, and sign is replaced the calling 1 of UE-A and the current existence of CS territory user;

Carry out the H248 operation between step 306, MGCF and IM-MGW, set up IM-MGW to the carrying between AS;

Step 307, MGCF act on behalf of the setup requests that CS territory user responds AS, successfully set up session 3 between MGCF, AS;

Step 308, AS send NOTIFY to UE-A, the progress of notice REFER request;

Step 309, MGCF use medium face RTP (RealtimeTransfer Protocol, the RTP) stream between that set up and the AS of session 3 to replace original medium face rtp streaming of calling out between 1 that set up and UE-A;

Step 310, MGCF are according to the session 1 of Replaces request end with UE-A, and session 1 discharges, and MGCF that original session 1 is set up and the medium face rtp streaming between UE-A are closed.

After the Replaces flow process took place, the original calling 1 between UE-A and the CS territory user was replaced by the new calling 3 between AS and the CS territory user, and UE-A and CS territory user change conference status over to from both sides' talking state, shown in Fig. 3 b and 3c.

As seen from the above description, when IMS territory and CS territory by the MGCF intercommunication Replaces take place, has tangible difference with the Replaces of inside, IMS territory.

At first, be increased to 5 nodes from 3 nodes on the call model, and increased MGCF, IM-MGW network element;

Secondly, because the existence of MGCF/IM-MGW, Replaces is transparent to the CS territory user of former calling, and in the IMS territory, user B need participate in the realization of Replaces, shown in Fig. 2 a;

At last, MGCF need can realize separating of signaling control and medium control by H248 agreement control IM-MGW, and the ordinary terminal in the IMS territory does not then have these needs, shown in Fig. 2 a, 2b and 2c.

Though 3GPP TS 24.147 has provided the IMS territory and intercommunication can be realized by MGCF/IM-MGW in the CS territory, and, realize calling out and replace by means of the Replaces function; But 3GPP TS 24.147 does not solve medium face passage and how to switch.

Therefore, prior art awaits to improve and development.

Summary of the invention

Problem to be solved by this invention is to provide a kind of method that the medium face switches that realizes in replacing function, this method can be under the MGCF/IM-MGW interworking situation, and when MGCF receives in the IMS territory Replaces request, realizes the switching of medium face passage.

In order to solve the problems of the technologies described above, technical scheme of the present invention comprises:

A kind of method that realizes the switching of medium face in replacing function, it comprises the steps:

The third party user of A, IMS domain side initiates the call request of newly-built session two to the MGCF network element, the session one between first user of request replacement circuit switching domain side and second user of described IMS domain side; It is to adopt following method that the carrying of described session one is set up: described IP multimedia gateway function network element is under the control of described MGCF network element, newly-built context one, and in described context one the newly-built terminal one that is connected with first user, and the terminal two that is connected with second user, described terminal one enters the bilateral state with terminal two;

B, according to the call request of described session two, IP multimedia gateway function network element carries out the carrying that described session two replaces described session one and switches under the control of described MGCF network element;

C, described first user and third party user enter the stable state session status of described session two, discharge described second user.

Described method wherein, also comprises step before the described steps A:

A0, by procotol, between described first user and described second user, set up described session one.

Described method wherein, comprises the load bearing process that makes up described session one in the described steps A 0, implementation step is as follows:

A01, by described MGCF network element, between described first user and second user, initiate to set up the call request of described session one;

A02, according to the call request of described session one, described IP multimedia gateway function network element makes up the carrying of described session one under the control of described MGCF network element.

Described method wherein, in the described steps A, comprises in the described call request being used to indicate the replacement head of replacing described session two, includes call identification, purpose label and source label in this replacement head.

Described method, wherein, among the described step B, described carrying handoff procedure comprises step:

B1, according to described replacement head, described IP multimedia gateway function network element newly-built context two under the control of described MGCF network element, and the terminal three that newly-built and described the 3rd user is connected in this context two;

B2, described terminal two is moved in the described context two from described context one, and make described terminal two isolated with terminal three;

B3, described terminal three is moved in the described context one from described context two, and described terminal one is connected with terminal three bilaterals.

Described method, wherein, before carrying out described carrying handoff procedure, if described first user or second user's off-hook comprise the steps: among the then described C

C11, described MGCF network element send the session turn-on response to described third party user, and described the 3rd user's loopback acknowledge message;

C12, described MGCF network element send the message that finishes described session one to described second user, and described second user's loopback success message;

C13, described IP multimedia gateway function network element discharge described context two and terminal two under the control of described MGCF network element.

Described method, wherein, before carrying out described carrying handoff procedure, if described second user off-hook not comprises step among the then described step C:

C21, described MGCF network element send the session turn-on response to described third party user, and described the 3rd user's loopback acknowledge message;

C22, described MGCF network element send response message to described first user;

C23, described MGCF network element send cancellation message to described second user, and cancel described second user and carry out described session one;

C24, described IP multimedia gateway function network element discharge described context two and terminal two under the control of described MGCF network element.

Described method, wherein, in the described steps A 01, the call request signaling of described session one adopt the ISUP signaling or with the call control signalling of bearer independent.

Adopt the method that the medium face switches that in replacing function, realizes of the present invention, and in IMS territory and CS territory by under the situation of MGCF/IM-MGW intercommunication, and MGCF receives when IMS territory Replaces asks, realize the switching of medium face passage between first, second and third side user, and then realized the session replacement.

Description of drawings

Fig. 1 is the structural representation that the MGCF/IM-MGW intercommunication is passed through in prior art IMS territory and CS territory;

Fig. 2 a is an existing IMS territory Replaces schematic flow sheet;

Fig. 2 b is before Replaces takes place among Fig. 2 a, the call model figure of IMS A and IMS B both sides talking state;

Fig. 2 c is after Replaces takes place among Fig. 2 a, the call model figure of IMS B and IMS C both sides talking state;

Fig. 3 a is that prior art is invited the realization flow figure of POTS (Plain Old Telephone Service) user to the session of IMS territory by MGCF/IM-MGW;

Fig. 3 b is before Replaces takes place among Fig. 3 a, the call model figure of UE-A and CS territory user both sides' talking state;

Fig. 3 c is that UE-A and CS territory user both sides entered the call model figure of conference status after Replaces took place among Fig. 3 a;

Fig. 4 is the call model figure of the inventive method;

Fig. 5 is in the inventive method, and the session 1 between CS B and IMS A is in talking state, and the call request of session one is when being initiated by CS B, realizes calling out replacing flow chart;

Fig. 6 is in the inventive method, and the session 1 between CS B and IMS A is in talking state, and the call request of session one is when being initiated by IMS A, realizes calling out replacing flow chart;

Fig. 7 is in the inventive method, when the session 1 between CS B and IMS A is in the unstable state session status, realizes calling out the replacement flow chart;

Fig. 8 is the state before the medium face handoff procedure of the inventive method begins; Newly-built context one (C1) schematic diagram; Wherein, T1-terminal one, the carrying B between Bearer B-and CS; T2-terminal two, the carrying A between Bearer A-and A;

Fig. 9 is in the medium face handoff procedure of the inventive method, newly-built context (C2) schematic diagram; Wherein, T3-terminal three, the carrying C between Bearer C-and third party user C;

Figure 10 is in the medium face handoff procedure of the inventive method, T2 is moved on among the C2 from C1, and make T2 and the isolated schematic diagram of T3;

Figure 11 is in the medium face handoff procedure of the inventive method, T3 is moved on among the C1 from C2, and make the schematic diagram of T1 and T3 bilateral;

Figure 12 is in the medium face handoff procedure of the inventive method, the schematic diagram after C2, T2 are released;

Figure 13 is the realization flow figure of the inventive method.

Embodiment

Below in conjunction with accompanying drawing, technical scheme of the present invention is described in further detail.

The invention provides a kind of method that the medium face switches that realizes in replacing function, the implementation procedure of this method adopts call model as described in Figure 4.Suppose three users, be respectively the first user B (CS B) in CS territory, the second user A (IMS A) in IMS territory and the third party user C (IMS C) in IMS territory; Wherein, by MGCF/IM-MGW, have session one (session 1) between CS B and IMS A, and IMS C initiates to set up the request of session two (session 2) by MGCF/IM-MGW to CS B, and carry Replaces header in this request, session 1 is replaced in indication.

As shown in figure 13, of the present inventionly a kind ofly realize that in replacing function the realization flow step of medium face changing method is as follows:

100, IMS C asks to replace the session 1 between CS B and IMS A to the call request that MGCF initiates newly-built session 2; Wherein, session 1 can be the stable state session, also can be the unstable state session;

200, according to the call request of described session 2, IM-MGW carries out the carrying switching that described session 1 is replaced in described session 2 under the control of MGCF;

300, CS B and IMS C enter the stable state call state of described session 2, discharge IMS A.

In the said method, before switching according to carrying session 1 of living in be stable state or unstable state, and the call request state of different user initiation session 1, can divide following several situation to carry out session and replace and discuss:

First kind of situation, IMS A off-hook, i.e. session 1 is the stable state session, and the call request of session 1 is when being initiated by CS B;

See also accompanying drawing 5, the flow process of utilizing the Replaces function to realize that the medium face switches comprises the steps:

501, CS B sends IAM (initial address message) to MGCF, sends call request, and request is set up session 1 with IMS A; The interoffice signaling of wherein said call request can be ISUP or BICC;

502, MGCF is according to described call request, the control newly-built context one of IM-MGW (C1), and in C1 newly-built terminal one (T1), between T1 and CS territory, set up simultaneously and carry B (BearerB);

503, MGCF invites (INVITE) by sending to IMS A, and request is established to the session 1 of IMS A;

504, MGCF controls IM-MGW newly-built terminal two (T2) in C1 according to described INVITE, and sets up carrying A (Bearer A) between T2 and IMS A, makes simultaneously between terminal T1 and the T2 and realizes bilateral, as shown in Figure 8; Wherein, mode is set up in the carrying of the IMS A in IMS territory description in RFC3264, and RFC3959, and the early-session that is introduced among the RFC3960 (medium early) function also can be regarded the part of BearerA as;

If 505 when existing the resource reservation process, MGCF will and IMS A between complete successfully resource reservation, be the creation precondition that IMS A sends ring; Wherein, resource reservation has description in RFC3312;

506, IMS A sends 180Ringing (ring) to MGCF, thereby makes the session 1 between MGCF and IMS A enter the ring attitude;

507, after MGCF receives 180 Ringing, send ACM (Address Complete Message) to CS B, like this, CS B just can hear ring-back tone, so far, calls out between CS B, IMS A and enters the ring unstable state;

508, IMS A sends 200 OK to MGCF, replys incoming call session 1;

509, after MGCF receives 200 OK, send response ACK (affirmation) to IMS A;

510, MGCF sends ANM (replying) response to CS B, and this moment, CS B and IMS A entered the call conversation state of session 1;

511, need set up session two (session 2) with CS B as IMS C, when replacing sessions 1 with session 2 simultaneously, IMS C sends the call request of session 2 to MGCF, and request is set up session 2 with CS B; Wherein, the call request of described session 2 comprises Replaces header (replacement head), replaces session 1 in order to indication, and includes callid, to-tag, from-tag among this Replaces header;

512, MGCF finds session to be replaced 1 according to the callid that comprises among the Replaces header, to-tag, from-tag, and further obtains the context C1 of session 1, terminal one T1 of CS territory side and the terminal two (T2) of IMS territory side, as shown in Figure 9; Simultaneously, MGCF is according to replacing call request, the context two (C2) of the newly-built session 2 of control IM-MGW, and in C2 newly-built terminal three (T3), and between T3 and IMS C, set up carrying C (Bearer C), because T3 is under the jurisdiction of new context C2, so the terminal T1 among T3 and the C1, T2 are isolated, as shown in Figure 9;

If 513 exist the resource reservation process, MGCF will and IMS C between complete successfully resource reservation, create preconditions for MGCF replys session 2;

514, MGCF control IM-MGW moves on to T2 among the C2 from C1, and makes T2 and T3 isolated, as shown in figure 10;

515, MGCF control IM-MGW moves on to T3 among the C1 from C2, and makes T1 and T3 realize bilateral, as shown in figure 11;

516, MGCF sends 200 OK to IMS C, replys session 2;

517, IMS C sends response ACK according to 200 OK that receive to MGCF.

518, MGCF use to finish that (BYE) mode discharges and IMS A between session 1;

519, IMS A returns 200 OK to MGCF, discharges the signaling of session 1;

520, after MGCF receives 200 OK, control IM-MGW discharges C2 and T2, and release Bearer A, as shown in figure 12, so far, CS B and IMS C enter talking state, and IMS A transfers Idle state to from talking state, thereby make IMS C use the Replaces function, successful replacement the session 1 between CS B and the IMS A.

Second kind of situation, CS B off-hook, i.e. session 1 is the stable state session, and the call request of session 1 is when being initiated by IMS A;

See also accompanying drawing 6, the flow process of utilizing the Replaces function to realize that the medium face switches comprises the steps:

601, IMS A sends INVITE to MGCF, and request is established to the session 1 of CS B;

602, the newly-built context C1 of MGCF control IM-MGW, newly-built therein terminal T2 carries BearerA between foundation and A

603, MGCF sends IAM to B;

604, MGCF control IM-MGW newly-built terminal T1 in C1 carries BearerB between foundation and B.Make T1 and T2 bilateral, as shown in Figure 8;

605, B ring is to MGCF loopback ACM;

606, MGCF sends 180Ringing to A;

607, B off-hook is to MGCF loopback ANM;

608, MGCF sends 200 OK to A;

609, A responds ACK to MGCF.So far, calling enters talking state between B, A;

610, need set up session two (session 2) with CS B as IMS C, when replacing sessions 1 with session 2 simultaneously, IMS C sends the call request of session 2 to MGCF, and request is set up session 2 with CS B; Wherein, the call request of described session 2 comprises Replaces header (replacement head), replaces session 1 in order to indication, and includes callid, to-tag, from-tag among this Replaces header;

611, MGCF finds session to be replaced 1 according to the callid that comprises among the Replaces header, to-tag, from-tag, and further obtains the context C1 of session 1, terminal one T1 of CS territory side and the terminal two (T2) of IMS territory side, as shown in Figure 9; Simultaneously, MGCF is according to replacing call request, the context two (C2) of the newly-built session 2 of control IM-MGW, and in C2 newly-built terminal three (T3), and between T3 and IMS C, set up carrying C (Bearer C), because T3 is under the jurisdiction of new context C2, so the terminal T1 among T3 and the C1, T2 are isolated, as shown in Figure 9;

If 612 exist the resource reservation process, MGCF will and IMS C between complete successfully resource reservation, create preconditions for MGCF replys session 2;

613, MGCF control IM-MGW moves on to T2 among the C2 from C1, and makes T2 and T3 isolated, as shown in figure 10;

614, MGCF control IM-MGW moves on to T3 among the C1 from C2, and makes T1 and T3 realize bilateral, as shown in figure 11;

615, MGCF sends 200 OK to IMS C, replys session 2;

616, IMS C sends response ACK according to 200 OK that receive to MGCF.

617, MGCF sends BYE to A, discharges session 1;

618, A responds 200 OK.

619, MGCF control IM-MGW discharges C2 and T2, and discharges Bearer A, as shown in figure 12, so far, CS B and IMS C enter talking state, and IMS A transfers Idle state to from conversation state, thereby make IMS C use the Replaces function, successful replacement the session 1 between CS B and the IMS A.

The third situation, IMS A is off-hook not, i.e. and session 1 is the unstable state session, and the call request of session 1 is when being initiated by CS B;

See also accompanying drawing 7, the flow process of utilizing the Replaces function to realize that the medium face switches comprises the steps:

701, CS B sends IAM (initial address message) to MGCF, sends call request, and request is set up session 1 with IMS A; The interoffice signaling of wherein said call request can be ISUP or BICC;

702, MGCF is according to described call request, the control newly-built context one of IM-MGW (C1), and in C1 newly-built terminal one (T1), between T1 and CS territory, set up simultaneously and carry B (BearerB);

703, MGCF invites (INVITE) by sending to IMS A, and request is established to the session 1 of IMS A;

704, MGCF controls IM-MGW newly-built terminal two (T2) in C1 according to described INVITE, and sets up carrying A (Bearer A) between T2 and IMS A, makes simultaneously between terminal T1 and the T2 and realizes bilateral, as shown in Figure 8; Wherein, mode is set up in the carrying of the IMS A in IMS territory description in RFC3264, and RFC3959, and the early-session that is introduced among the RFC3960 (medium early) function also can be regarded the part of BearerA as;

If 705 when existing the resource reservation process, MGCF will and IMS A between complete successfully resource reservation, be the creation precondition that IMS A sends ring; Wherein, resource reservation has description in RFC3312;

706, IMS A sends 180Ringing (ring) to MGCF, thereby makes the session 1 between MGCF and IMS A enter the ring attitude;

707, after MGCF receives 180 Ringing, send ACM (Address Complete Message) to CS B, like this, CS B just can hear ring-back tone; So far, calling enters the ring unstable state between B, A.

708, need set up session two (session 2) with CS B as IMS C, when replacing sessions 1 with session 2 simultaneously, IMS C sends the call request of session 2 to MGCF, and request is set up session 2 with CS B; Wherein, the call request of described session 2 comprises Replaces header (replacement head), replaces session 1 in order to indication, and includes callid, to-tag, from-tag among this Replaces header; 709, MGCF finds session to be replaced 1 according to the callid that comprises among the Replaces header, to-tag, from-tag, and further obtains the context C1 of session 1, terminal one T1 of CS territory side and the terminal two (T2) of IMS territory side, as shown in Figure 9; Simultaneously, MGCF is according to replacing call request, the context two (C2) of the newly-built session 2 of control IM-MGW, and in C2 newly-built terminal three (T3), and between T3 and IMS C, set up carrying C (Bearer C), because T3 is under the jurisdiction of new context C2, so the terminal T1 among T3 and the C1, T2 are isolated, as shown in Figure 9;

If 710 exist the resource reservation process, MGCF will and IMS C between complete successfully resource reservation, create preconditions for MGCF replys session 2;

711, MGCF control IM-MGW moves on to T2 among the C2 from C1, and makes T2 and T3 isolated, as shown in figure 10;

712, MGCF control IM-MGW moves on to T3 among the C1 from C2, and makes T1 and T3 realize bilateral, as shown in figure 11;

713, MGCF sends 200 OK to IMS C, replys session 2;

714, IMS C sends response ACK according to 200 OK that receive to MGCF.

715, MGCF sends ANM (replying) response to CS B.

716, MGCF sends CANCEL to IMS A, and the unstable state between cancellation and IMS A calls out 1;

717, IMS A sends 200 OK to MGCF, echo canceling session 1;

718, IMS A sends 487 Request Terminated (request stops) session 1 to MGCF;

719, MGCF sends ACK to IMS A, confirms session 1 cancellation;

720, MGCF control IM-MGW discharges C2 and T2, and discharges Bearer A, as shown in figure 12, so far, CS B and IMS C enter talking state, and IMS A transfers Idle state to from unstable state, thereby make IMS C use the Replaces function, successful replacement the session 1 between CS B and the IMS A.

In sum, adopt the method that the medium face switches that in replacing function, realizes of the present invention, IMS territory and CS territory are being passed through under the situation of MGCF/IM-MGW intercommunication, when MGCF receives IMS territory Replaces request, realized the carrying of medium face passage between first, second and third side user is switched, and then realized the session replacement; Simultaneously, this method is simple to operate, and is easy to implement, and remedied the blank that in the existing protocol standard Replaces function in IMS territory is expanded to the intercommunication occasion in IMS territory and CS territory.

Should be understood that, for those of ordinary skills, can be improved according to the above description or conversion, and all these improvement and conversion all should belong to the protection range of claims of the present invention.

Claims

1. realize the method that the medium face switches for one kind in replacing function, it comprises the steps:

2. method according to claim 1 is characterized in that, also comprises step before the described steps A:

3. method according to claim 2 is characterized in that, comprises the load bearing process that makes up described session one in the described steps A 0, and implementation step is as follows:

4. method according to claim 3 is characterized in that, in the described steps A, comprises in the call request of described session two being used to indicate the replacement head of replacing described session one, includes call identification, purpose label and source label in this replacement head.

5. method according to claim 4 is characterized in that, among the described step B, described carrying handoff procedure comprises step:

6. method according to claim 5 is characterized in that, before carrying out described carrying handoff procedure, if described first user or second user's off-hook comprise the steps: among the then described C

C11, described MGCF network element send the session turn-on response to described third party user, and described third party user's loopback acknowledge message;

7. method according to claim 5 is characterized in that, before carrying out described carrying handoff procedure, if described second user off-hook not comprises step among the then described step C:

C21, described MGCF network element send the session turn-on response to described third party user, and described third party user's loopback acknowledge message;

8. method according to claim 3 is characterized in that, among the described A01, the call request signaling of described session one adopt the ISUP signaling or with the call control signalling of bearer independent.