CN102761929A

CN102761929A - Realizing method of IMS (IP multimedia core network subsystem) session switching and access switching control function

Info

Publication number: CN102761929A
Application number: CN2012102355786A
Authority: CN
Inventors: 杨强; 王忱
Original assignee: ZTE Corp
Current assignee: ZTE Corp
Priority date: 2012-07-09
Filing date: 2012-07-09
Publication date: 2012-10-31
Anticipated expiration: 2032-07-09
Also published as: CN102761929B

Abstract

The invention provides a realizing method of IP (IP multimedia core network subsystem) multimedia subsystem session switching. The method comprises the steps that an ATCF (access transfer control function) switches specified session of a user from a first access network to a second access network after receiving session switching request information of the first access network and the second access network; the ATCF determines whether to release specified session of the first access network according to local policies, and if the specified session of the first access network is determined to be released, the session is released; the ATCF determines whether to inform an application server relevant to the user according to the local policies, and an access network of the user is changed; and the first access network and the second access network are respectively a PS (packet switch) access network and a CS (circuit switch) access network. The invention also provides an access switching control function. By adopting the method, not only more rapid switching that an SRVCC (single radio voice call continuity) technology can be realized, but also certain signaling interaction processes can be reduced relative to eSRVCC (evolved single radio voice call continuity).

Description

IMS session switching method and access switching control function

Technical field

The present invention relates to the communications field; Relate to IP Multimedia System (IP Multimedia Core Network Subsystem more specifically; Abbreviation IMS) conversation switching method of network and ATCF (Access Transfer Control Function inserts switching control function).

Background technology

IMS is by third generation partner program (3rd Generation Partnership Project; Abbreviation 3GPP) a kind of IP-based network framework of tissue proposition; It has made up an opening and service environment flexibly, supports multimedia application, and abundant multimedia service is provided for the user.

At present; Mobile communication with circuit switching (Circuit Switch, CS) network is main, like global system for mobile communications (GSM) and code division multiple access (CDMA) etc.; Standard and the patent of IMS have been inserted at present through CS relevant for UE (User Equipment, subscriber equipment).

In standards such as TS 24.292,3GPP TS 23.237 and 3GPP TS 24.237, had use ATCF realize packet switching (Packet Switch, PS) and signaling of switching between the CS and flow process description.

The problem that prior art exists:

1) if use SRVCC (Single Radio Voice Call Continuity, single wireless continuous voice call) technology, session is switched slower, and it is relatively poor that the user experiences.

2) if use eSRVCC (Evolved SRVCC; The SRVCC of evolution) technology; Need cooperating and interacting message between ATCF and the SCC AS (Service Centralization and Continuity Application Server, professional continuous and pooled applications server) in registration, eSRVCC ability notice and in switching.

3) do not carry out CS access registration and PS access registration and registration subscription related at S-CSCF (Serving Call Session Control Function, service call conversation control function).

4) except that SCC AS, other and user-dependent AS (Application Server, application server) do not have the perception user access networks that change has taken place.

5) because the reason of (3) and (4), except that SCC AS, the registration among other and the user-dependent AS can not periodically be refreshed, and causes calling or partial service correctly not to realize.

Summary of the invention

The technical problem that the present invention will solve provides a kind of IMS session switching method and ATCF, to adapt to the calling handoff requirement of eSRVCC.

In order to address the above problem, the invention provides a kind of IP Multimedia System session switching method, comprising:

Insert switching control function ATCF and receive first Access Network after the session handoff request message of second Access Network, user's specified session is switched to second Access Network from first Access Network;

Said ATCF determines whether to discharge the said specified session of said first Access Network according to local policy, if then carry out session and discharge;

Said ATCF determines whether notice and said user-dependent application server according to local policy, said user's Access Network change;

Said first Access Network is the circuit switching Access Network, and said second Access Network is the packet switching Access Network, perhaps; Said first Access Network is the packet switching Access Network, and said second Access Network is the circuit switching Access Network.

Further, said method also can have following characteristics, and said specified session with the user switches to second Access Network from first Access Network and comprises:

Said ATCF switches to second Access Network with said user's specified session from first Access Network according to the mode of grappling medium or not grappling medium.

Further, said method also can have following characteristics, and said method also comprises:

When said ATCF switches other sessions of said user according to local policy is definite, the session information that the notice related network elements need switch; And,

Follow-up said ATCF switches to second Access Network with corresponding session from first Access Network after receiving the session handoff request message of said related network elements; Determine whether to discharge the said corresponding session of said first Access Network according to local policy, if carry out session and discharge; Determine whether notice and said user-dependent application server according to local policy, said user's Access Network change;

Said related network elements is the eMSC of mobile switching centre or the MGCF MGCF or the Proxy Call Session Control Function P-CSCF of evolution.

Further, said method also can have following characteristics, and the session information that said ATCF notice related network elements need switch comprises:

Said ATCF carries the sign that all sessions of said user is switched to said second Access Network in notification message; Perhaps, carry the session related information that one or more needs switch to said second Access Network.

Further; Said method also can have following characteristics; Said method also comprises, after said ATCF receives said registration request from user message, initiates registration through query call conversation control function I-CSCF and service call conversation control function S-CSCF to home subscriber server HSS; Receive the response message that succeeds in registration that said HSS returns, carry said user in the said response message that succeeds in registration and whether support the relevant information switched between first Access Network and second Access Network.

Further, said method also can have following characteristics, and said ATCF determines whether notice and said user-dependent application server according to local policy, and said user's Access Network change comprises:

Said ATCF is when confirming notice with said user-dependent application server; Through in revising media information reINVITE or informational message INFO or updating message UPDATE, carrying designated identification notice and said user-dependent application server, said user's Access Network change.

The embodiment of the invention also provides a kind of access switching control function, and said access switching control function ATCF comprises handover module, session release module and notification module, wherein:

Said handover module is used for: receive first Access Network after the session handoff request message of second Access Network, user's specified session is switched to second Access Network from first Access Network;

Said session release module is used for: determine whether to discharge the said specified session of said first Access Network according to local policy, if carry out session and discharge;

Said notification module is used for, and determines whether notice and said user-dependent application server according to local policy, said user's Access Network change;

Wherein, said first Access Network is the circuit switching Access Network, and said second Access Network is the packet switching Access Network, perhaps; Said first Access Network is the packet switching Access Network, and said second Access Network is the circuit switching Access Network.

Further, above-mentioned access switching control function also can have following characteristics, and said handover module switches to second Access Network with user's specified session from first Access Network and comprises:

Said handover module switches to second Access Network with said user's specified session from first Access Network according to the mode of grappling medium or not grappling medium.

Further, above-mentioned access switching control function also can have following characteristics, and said handover module also is used for, when other sessions of said user being switched according to local policy is definite, and the session information that the notice related network elements need switch; And, after the follow-up session handoff request message that receives said related network elements, other sessions of said user are switched to second Access Network from first Access Network;

Said session release module also is used for, and determines whether to discharge said other sessions of said first Access Network according to local policy; If carry out session and discharge;

Said notification module also is used for, and after said handover module switches to second Access Network with other sessions of said user from first Access Network, determines whether notice and said user-dependent application server according to local policy, said user's Access Network change;

Further, above-mentioned access switching control function also can have following characteristics, and the session information that said handover module notice related network elements need switch comprises:

Said handover module carries the sign that all sessions of said user is switched to said second Access Network in notification message; Perhaps, carry the session related information that one or more needs switch to said second Access Network.

Further; Above-mentioned access switching control function also can have following characteristics; Said ATCF also comprises Registering modules; After being used to receive said registration request from user message; Initiate registration through query call conversation control function I-CSCF and service call conversation control function S-CSCF to home subscriber server HSS, receive the response message that succeeds in registration that said HSS returns, carry said user in the said response message that succeeds in registration and whether support the relevant information switched between first Access Network and second Access Network.

Further, above-mentioned access switching control function also can have following characteristics, and said notification module determines whether notice and said user-dependent application server according to local policy, and said user's Access Network change comprises:

Said notification module is when confirming notice with said user-dependent application server; Through in revising media information reINVITE or informational message INFO or updating message UPDATE, carrying designated identification notice and said user-dependent application server, said user's Access Network change.

Utilize the present invention, in the 200ok message that obtains succeeding in registration, can learn whether the user has ability and the relevant information of switching between PS and the CS.If prior art needs to wait for the message message that comes from SCCAS.Simultaneously, also saved S-CSCF and initiated tripartite registration to SCC AS, and the flow process of SRVCC information synchronously between SCC AS and the HSS.

Utilize the present invention, in calling out switching, can realize switching more fast, also can reduce some Signalling exchange flow processs for eSRVCC than SRVCC technology.

Utilize the present invention, in calling, after the user realizes that Access Network switches, can realize normally calling out and other business, can not exceed the time limit to cause to call out to discharge and maybe can not realize some business because of registration.

Utilize the present invention, for existing eSRVCC technology, need not dispose SCC AS network element.

Description of drawings

The PS access registration flow process that Fig. 1 participates in for ATCF;

The CS access registration flow process that Fig. 2 participates in for ATCF;

Fig. 3 realizes inserting the call flow that switches to the CS access by PS for using ATCF;

Fig. 4 realizes inserting the call flow that switches to the PS access by CS for using ATCF;

Fig. 5 realizes inserting the call flow that switches to the CS access by PS for using not grappling of ATCF medium;

Fig. 6 realizes inserting the call flow that switches to the PS access by CS for using not grappling of ATCF medium;

The mid-call PS-CS switching flow that Fig. 7 participates in for ATCF;

The mid-call CS-PS switching flow that Fig. 8 participates in for ATCF;

Fig. 9 is an embodiment of the invention ATCF block diagram.

Embodiment

For making the object of the invention, technical scheme and advantage clearer, hereinafter will combine accompanying drawing that embodiments of the invention are elaborated.Need to prove that under the situation of not conflicting, embodiment among the application and the characteristic among the embodiment be combination in any each other.

The embodiment of the invention is equipment and the system of switching between a brand-new support PS and the CS, but for ease of understanding, follows the title ATCF that present prior art is used.Need to prove,, compare to have improvement with existing ATCF though still be referred to as ATCF in the embodiment of the invention.

In the embodiment of the invention, through in PS-CS switches, realize that by ATCF the registration of former Access Network and subscription refresh the user.On this basis, realize to call out handoff functionality, the participation of the SCC AS network element that does not need in the prior art to be comprised by ATCF.

According to local policy, ATCF sends message can for other network element, to inform the user conversation Access Network switching has taken place.

The embodiment of the invention provides a kind of IP Multimedia System session switching method, comprising:

Wherein, said specified session with the user switches to second Access Network from first Access Network and comprises:

Wherein, when said ATCF switches other sessions of said user according to local policy is definite, the session information that the notice related network elements need switch; And,

Wherein, said ATCF notifies the session information that related network elements need switch to comprise:

Said ATCF carries the sign that all sessions of said user is switched to said second Access Network in notification message; Perhaps, carry the session related information that one or more needs switch to said second Access Network.Said notification message can be a refer message.

Wherein, Said method also comprises; After said ATCF receives said registration request from user message; Initiate registration through query call conversation control function I-CSCF and service call conversation control function S-CSCF to home subscriber server HSS, receive the response message that succeeds in registration that said HSS returns, carry said user in the said response message that succeeds in registration and whether support the relevant information switched between first Access Network and second Access Network.

Wherein, said ATCF determines whether notice and said user-dependent application server according to local policy, and said user's Access Network change comprises:

The PS access registration flow process that Fig. 1 participates in for ATCF.

Step 101, ATCF receives the login request message that comes from P-CSCF (Proxy Call Session Control Function, Proxy Call Session Control Function).

Step 102, by prior art, ATCF carries the relevant information of switching between PS-CS in the login request message of issuing I-CSCF (Interrogating Call Session Control Function, query call conversation control function).

Step 103-105, HSS carry the relevant information (promptly whether supporting eSRVCC information shown in the figure) whether this user supports to switch between PS-CS in returning to the response message that succeeds in registration of S-CSCF, and are recorded in the network element such as ATCF.Flow process illustrates: issue at S-CSCF among the SAR (Server-Assignment-Request, server-assignment request) of HSS and carry STN-SR (Session Transfer Number-Single Radio, session Handover Number-single is wireless) parameter; Issue at HSS in SAA (Server-Assignment-Answer, the server-assignment is replied) message of S-CSCF and carry C-MSISDN (Correlation MSISDN, related mobile number MSISDN) parameter.S-CSCF carries the C-MSISDN parameter in the registration reply message of issuing ATCF through I-CSCF.ATCF uses C-MSISDN in PS-CS switches.

Step 106, ATCF gives the success response of user's re-injection volume.

The CS access registration flow process that Fig. 2 participates in for ATCF.

Step 201, ATCF receives the login request message that comes from eMSC Server (Mobile Switching Center Server of evolution).

Step 202, by prior art, ATCF carries the relevant information of switching between CS-PS in issuing the I-CSCF login request message.

Step 203-205, HSS carry this user and whether support the relevant information switched between CS-PS, and be recorded in the network elements such as ATCF in returning to the response message that succeeds in registration of S-CSCF.Flow process illustrates: in S-CSCF issues the SAR of HSS, carry STN-SR (or/and STI-rSR) parameter; , HSS carries the C-MSISDN parameter in issuing the SAA message of S-CSCF.S-CSCF carries the C-MSISDN parameter in the registration reply message of issuing ATCF through I-CSCF.ATCF uses C-MSISDN in CS-PS switches.

Step 206, ATCF gives the success response of user's re-injection volume.

Fig. 3 realizes inserting the call flow that switches to the CS access by PS for using ATCF.

Step 301, ATCF receives the PS-CS session handoff request message that comes from eMSC Server or MGCF (Media Gateway Control Function, MGCF).

Step 302-303, ATCF realizes that according to prior art (using ATGW grappling media mode) conversation media switches, and answers response to user response.

Step 304-305, ATCF determines whether to discharge PS according to local policy and inserts session.Among figure 304 and 305 flow processs are for discharging PS session flow process.

Step 306, ATCF determines whether other network element of notice (such as using informational message info or updating message update) according to local policy, change has taken place in user's Access Network.

Said other network elements are user-dependent application server, comprise S-CSCF, and other application servers.

Flow is identical with existing related specifications, omits.

Wherein, the main distinction with prior art is that ATCF need not initiate new the calling for PS-CS switches to SCC AS.

Fig. 4 realizes inserting the call flow that switches to the PS access by CS for using ATCF.

Step 401, ATCF receives the CS-PS session handoff request message that comes from P-CSCF.

Step 402-403, ATCF switches according to the existing techniques in realizing session.

Step 404-405, ATCF determines whether to discharge CS according to local policy and inserts session.Among figure 404 and 405 flow processs are for discharging CS session flow process.

Step 406, ATCF determines whether to notify other network element according to local policy, and change has taken place in user's Access Network.

Flow is identical with existing related specifications, omits.

Wherein, the main distinction with prior art is that ATCF need not initiate new the calling for CS-PS switches to SCC AS.

Fig. 5 realizes inserting the call flow that switches to the CS access by PS for using not grappling of ATCF medium.

Step 501, ATCF receives PS-CS session handoff request (INVITE) message that comes from eMSC Server or MGCF.

Step 502-503, ATCF carries out media negotiation with SDP (Session Description Protocol, Session Description Protocol) information and the far-end in the INVITE of receiving.Concrete media negotiation mode, the present invention does not limit.

Step 504 is successfully realizing under the situation of media negotiation with far-end, and ATCF responds for eMSC Server or MGCF and answers response message 200OK.

Step 505-506, ATCF determines whether to discharge PS according to local policy and inserts session.Among figure 505 and 506 flow processs are for discharging PS session flow process.

Step 507, ATCF determines whether to notify other network element according to local policy, and change has taken place in user's Access Network.

Flow is identical with existing related specifications, omits.

Fig. 6 realizes inserting the call flow that switches to the PS access by CS for using not grappling of ATCF medium.

Step 601, ATCF receives CS-PS session handoff request (INVITE) message that comes from P-CSCF.

Step 602-603, ATCF carries out media negotiation with SDP information and the far-end in the INVITE of receiving.Concrete media negotiation mode, the present invention does not limit.

Step 604 is successfully realizing under the situation of media negotiation with far-end, and ATCF responds to P-CSCF and answers response message 200OK.

Step 605-606, ATCF determines whether to discharge CS according to local policy and inserts session.Among figure 605 and 606 flow processs are for discharging CS session flow process.

Step 607, ATCF determines whether to notify other network element according to local policy, and change has taken place in user's Access Network.

Flow is identical with existing related specifications, omits.

The mid-call PS-CS switching flow that Fig. 7 participates in for ATCF.

Step 701, ATCF receives the PS-CS session handoff request message that comes from eMSC or MGCF.

Step 702-703, ATCF use the mode of ATGW grappling medium to realize the session switching according to prior art and local logic.

Step 704-705, ATCF determines whether to discharge PS according to local policy and inserts session.Among figure 704 and 705 flow processs are for discharging PS session flow process.

Step 706, ATCF determines whether to notify other network element according to local policy, and change has taken place in user's Access Network.

Step 707-708, ATCF confirms other session of same user is switched according to local policy.Among the figure 707 needs to switch for notifying eMSC or which session of MGCF, and advice method comprises:

In refer message, carry and let all sessions of same user all switch to the sign of CS Access Network;

In refer message, carry the session related information that a plurality of switchings switch to the CS Access Network,, comprise the label (tag) of session identification (call-id), from, to header field such as dialog information, or the like.

In refer message, carry a switching and switch to the dialog information of CS Access Network.

Step 709-712, ATCF receive a handover request INVITE, have carried the information corresponding with refer in this INVITE.ATCF is according to local policy or related specifications, judges that this switches not use ATGW grappling medium.

Step 713-714, ATCF determines whether to discharge PS according to local policy and inserts session.Among figure 713 and 714 flow processs are for discharging PS session flow process.

Step 715, ATCF determines whether to notify other network element according to local policy, and change has taken place in user's Access Network.

Flow is identical with existing related specifications, omits.

Wherein, the main distinction with prior art is that ATCF need not initiate new the calling for PS-CS switches to SCC AS;

Carry the information of switching whole sessions or a plurality of sessions in the refer message, also comprise corresponding information in the handoff request invite message, so that ATCF identification.

Only enumerated the switching of two sessions among this figure; If ATCF receives a plurality of sessions switching invite request; ATCF does being similar to second session hand-off process (also can adopt ATGW grappling media mode to some switching, judgment rule uses existing standard or local policy) according to local logic.

Use grappling medium are switched in first session among this figure, and not grappling medium are switched in second session, mainly are the flexibilities that realizes for embodying, and are not so limited in actual the use.

The mid-call CS-PS switching flow that Fig. 8 participates in for ATCF.

Step 801, ATCF receives the CS-PS session handoff request message that comes from P-CSCF.

Step 802-803, ATCF use the method for ATGW grappling medium to realize the session switching according to prior art and local logic.

Step 804-805, ATCF determines whether to discharge CS according to local policy and inserts session.Among figure 804 and 805 flow processs are for discharging CS session flow process.

Step 806, ATCF determines whether to notify other network element according to local policy, and change has taken place in user's Access Network.

Step 807-808, ATCF confirms other session of same user is switched according to local policy.Among the figure 807 for which session of notice P-CSCF needs to switch, and advice method comprises:

In refer message, carry and let all sessions of same user all switch to the sign of PS Access Network;

In refer message, carry a plurality of switchings and switch to the dialog information of PS Access Network.

In refer message, carry a switching and switch to the dialog information of PS Access Network.

Step 809-812, ATGCF receive a handover request INVITE, have carried the information corresponding with refer in this INVITE.ATGCF is according to local policy or related specifications, judges that this switches not use ATGW grappling medium.

Step 813-814, ATCF determines whether to discharge CS according to local policy and inserts session.Among figure 813 and 814 flow processs are for discharging CS session flow process.

Step 815, ATCF determines whether to notify other network element according to local policy, and change has taken place in user's Access Network.

Flow is identical with existing related specifications, omits.

Wherein, the main distinction with prior art is that ATCF need not initiate new the calling for CS-PS switches to SCC AS;

Carry the sign of switching whole sessions in the refer message, perhaps, carry the information of switching one or more sessions, also comprise corresponding information in the handoff request invite message, so that ATCF identification.

Only enumerated the switching of two sessions among this figure; If ATCF receives a plurality of sessions switching invite request; ATCF does being similar to second session hand-off process (can adopt ATGW grappling media mode to some switching, judgment rule uses existing standard or local policy) according to local logic.

The embodiment of the invention provides a kind of access switching control function, and is as shown in Figure 9, and said access switching control function ATCF comprises handover module, session release module and notification module, wherein:

Wherein, said handover module switches to second Access Network with user's specified session from first Access Network and comprises:

Wherein, said handover module also is used for, when other sessions of said user being switched according to local policy is definite, and the session information that the notice related network elements need switch; And, after the follow-up session handoff request message that receives said related network elements, other sessions of said user are switched to second Access Network from first Access Network;

Wherein, said handover module notifies the session information that related network elements need switch to comprise:

Wherein, Said ATCF also comprises Registering modules; After being used to receive said registration request from user message; Initiate registration through query call conversation control function I-CSCF and service call conversation control function S-CSCF to home subscriber server HSS, receive the response message that succeeds in registration that said HSS returns, carry said user in the said response message that succeeds in registration and whether support the relevant information switched between first Access Network and second Access Network.

Wherein, said notification module determines whether notice and said user-dependent application server according to local policy, and said user's Access Network change comprises:

Need to prove, above-mentionedly be merely schematic illustration of the present invention, so:

Flow process among the embodiment is an exemplary flow.

Authentication whether in the registration/subscription embodies in exemplary flow, also can increase relevant authorizing procedure.

Message between each network element among the embodiment mainly is in order clearly to represent the thought of obtaining and calling out switching of Access Network handover information.In concrete realization, be not limited to these network elements and message.

For the abnormal conditions that occur in the various flow processs, the sequencing of some message under the situation of not conflicting, concrete restriction is not done in the concrete realization of each network element internal.

If the user supports the Access Network of ring attitude to switch, ATCF gives local terminal information that (initiating to insert the network element of switch sides) sent out and the same prior art of grappling medium whether.Different with prior art is, does not use SCC AS in the switching, switches which session and is confirmed by ATCF (rather than by SCC AS).

Switching has taken place to the Access Network of NE User in the notice back, and multiple mode can be arranged, such as can in revising media information reINVITE or other message (such as INFO, UPDATE), carrying respective identification.

In realization, ATCF and P-CSCF both can unify, and also can separate.

In realization; Inserting through CS under the situation of not supporting to register; ATCF can also initiate refresh registration to determine whether the agency according to local policy, perhaps adopts other network element of info/update message untill further notice under the situation that calling switches, not discharge the session that registration is exceeded the time limit.

One of ordinary skill in the art will appreciate that all or part of step in the said method can instruct related hardware to accomplish through program, said program can be stored in the computer-readable recording medium, like read-only memory, disk or CD etc.Alternatively, all or part of step of the foregoing description also can use one or more integrated circuits to realize.Correspondingly, each the module/unit in the foregoing description can adopt the form of hardware to realize, also can adopt the form of software function module to realize.The present invention is not restricted to the combination of the hardware and software of any particular form.

Claims

1. an IP Multimedia System session switching method is characterized in that, comprising:

2. the method for claim 1 is characterized in that, said specified session with the user switches to second Access Network from first Access Network and comprises:

3. the method for claim 1 is characterized in that, said method also comprises:

4. method as claimed in claim 3 is characterized in that, the session information that said ATCF notice related network elements need switch comprises:

5. like the arbitrary described method of claim 1 to 4; It is characterized in that; Said method also comprises, after said ATCF receives said registration request from user message, initiates registration through query call conversation control function I-CSCF and service call conversation control function S-CSCF to home subscriber server HSS; Receive the response message that succeeds in registration that said HSS returns, carry said user in the said response message that succeeds in registration and whether support the relevant information switched between first Access Network and second Access Network.

6. like the arbitrary described method of claim 1 to 4, it is characterized in that said ATCF determines whether notice and said user-dependent application server according to local policy, said user's Access Network change comprises:

7. one kind is inserted switching control function, it is characterized in that said access switching control function ATCF comprises handover module, session release module and notification module, wherein:

8. access switching control function as claimed in claim 7 is characterized in that, said handover module switches to second Access Network with user's specified session from first Access Network and comprises:

9. access switching control function as claimed in claim 7 is characterized in that,

Said handover module also is used for, when other sessions of said user being switched according to local policy is definite, and the session information that the notice related network elements need switch; And, after the follow-up session handoff request message that receives said related network elements, other sessions of said user are switched to second Access Network from first Access Network;

10. access switching control function as claimed in claim 9 is characterized in that, the session information that said handover module notice related network elements need switch comprises:

11. like the arbitrary described access switching control function of claim 7 to 10; It is characterized in that; Said ATCF also comprises Registering modules; After being used to receive said registration request from user message; Initiate registration through query call conversation control function I-CSCF and service call conversation control function S-CSCF to home subscriber server HSS, receive the response message that succeeds in registration that said HSS returns, carry said user in the said response message that succeeds in registration and whether support the relevant information switched between first Access Network and second Access Network.

12., it is characterized in that said notification module determines whether notice and said user-dependent application server according to local policy like the arbitrary described access switching control function of claim 7 to 10, said user's Access Network change comprises: