Method, user equipment and server for multimedia session transfer

1. A method for multimedia session transfer by a server, comprising:

receiving, by the server, a session transfer request sent by a User Equipment (UE), wherein the session transfer request carries a static Session Transfer Identifier (STI);

executing, by the server, a procedure for transferring an active Circuit Switched CS) session according to the static STI;

sending by the server, to the UE, a dynamic STI allocated to a held CS session during a session transfer; and

receiving, by the server, another session transfer request sent by the UE, wherein the other session transfer request carries the dynamic STI sent to the UE during the session transfer; and

executing, by the server, a procedure for transferring the held CS session according to the received other session transfer request carrying the dynamic STI.

2. The method according to claim 1 , wherein:

the dynamic STI is allocated by the server to the held CS session at time of setting up a call connection of the held CS session, or allocated by the server to the held CS session temporarily according to a judgment result.

3. The method according to claim 2 , wherein the step of sending the dynamic STI allocated to the held CS session to the UE is any one step of:

using a Contact header field, or a Replace header field, or a Target-Dialog header field of a response message in response to the CS session transfer request that carries the static STI to carry the dynamic STI, where the dynamic STI is allocated by the server to an access leg that is set up for the CS session transfer request that carries the static STI, and using such a header field to carry the dynamic STI allocated to the held CS session, wherein order of the two dynamic STIs is preset; and

using the Contact header field of the response message in response to the CS session transfer request that carries the static STI to carry the dynamic STI, where the dynamic STI is allocated by the server to the access leg that is set up for the CS session transfer request that carries the static STI, and using the Replace header field or the Target-Dialog header field to carry the dynamic STI allocated to the held CS session; and

sending a Refer message to the UE, and using a Refer-To header field of the Refer message to carry the dynamic STI allocated to the held CS session.

4. The method according to claim 1 , wherein the step of sending the dynamic STI allocated to the held CS session to the UE is any one step of:

using a Contact header field, or a Replace header field, or a Target-Dialog header field of a response message in response to the CS session transfer request that carries the static STI to carry the dynamic STI, where the dynamic STI is allocated by the server to an access leg that is set up for the CS session transfer request that carries the static STI, and using such a header field to carry the dynamic STI allocated to the held CS session, wherein order of the two dynamic STIs is preset;

using the Contact header field of the response message in response to the CS session transfer request that carries the static STI to carry the dynamic STI, where the dynamic STI is allocated by the server to the access leg that is set up for the CS session transfer request that carries the static STI, and using the Replace header field or the Target-Dialog header field to carry the dynamic STI allocated to the held CS session; and

sending a Refer message to the UE, and using a Refer-To header field of the Refer message to carry the dynamic STI allocated to the held CS session.

5. A server for multimedia session transfer, comprising:

a first module, adapted to:

receive a session transfer request sent by a User Equipment (UE), wherein the session transfer request carries a static Session Transfer Identifier (STI);

execute a procedure for transferring the active Circuit Switched (CS) session according to the static STI; and

a second module, adapted to:

send, to the UE, a dynamic STI allocated to a held CS session during a session transfer;

receive another session transfer request sent by the UE, wherein the another session transfer request carries the dynamic STI sent to the UE during the session transfer; and

execute a procedure for transferring the held CS session according to the another session transfer request carrying the dynamic STI.

6. A User Equipment (UE) for multimedia session transfer, comprising:

the transferring module, adapted to:

send a CS session transfer request that carries a static Session Transfer Identifier (STI) to a server,

execute a procedure corresponding to the CS session transfer request that carries the static STI,

receive a dynamic STI allocated to a held CS session from the server during a session transfer,

send, to the server, another CS session transfer request by using the dynamic STI received during the session transfer, and

execute a procedure corresponding to the another CS session transfer request sent to the server.

7. The UE according to claim 6 , wherein the transferring module further comprises any one of:

a judging module, adapted to: judge whether to send the CS session transfer request again according to the number of dynamic STIs carried in a response message from the server; if two dynamic STIs exist, retrieve a dynamic STI intended for a held CS session according to set order, and send a request again for transferring the held CS session by using the dynamic STI; and

judge whether to send the CS session transfer request again according to whether a Replace header field or a Target-Dialog header field a the response message from the server carries the dynamic STI allocated to the held CS session.