INTER-SUBSYSTEM TRANSFERS

• US 20090207807A1
• Filed: 06/08/2007
• Published: 08/20/2009
• Est. Priority Date: 06/14/2006
• Status: Active Grant

• Current Assignee: Apple Inc.
• Original Assignee: Nortel Networks Limited (Nortel Networks Corporation)
• Inventors: Stegall, Mark, Mahdi, Kaniz, Stojanovski, Saso
• Granted Patent: US 8,687,587 B2
• Time in Patent Office: Days
• US Class Current: 370/331
• CPC Class Codes: H04L 12/66 Arrangements for connecting between networks having differing types of switching systems, e.g. gateways
• CPC Class Codes: H04L 65/1086 session scope modification
• CPC Class Codes: H04W 36/0022 for transferring data sessions between adjacent core network technologies
• CPC Class Codes: H04W 36/00224 between packet switched [PS] and circuit switched [CS] network technologies, e.g. circuit switched fallback [CSFB]

Abstract

In general, the present invention provides for a direct inter-subsystem transfer of an active communication session, such as a call, between a packet subsystem (PS) and a circuit-switched subsystem (CS) in an efficient and effective manner while maintaining service control and continuity. Further, the inter-subsystem transfer may take place between a PS of one generation and a CS of another generation.

Claims

1. A method for facilitating inter-subsystem handovers between a circuit-switched subsystem and a packet subsystem while maintaining service control comprising:

anchoring session signaling for a communication session established between a user element and a remote endpoint in a multimedia subsystem;

providing centralized service control for the communication session from the multimedia subsystem when the user element is served by the circuit-switched subsystem and when the user element is served by the packet subsystem; and

during the communication session, effecting a radio layer handover of the user element from a transferring-out subsystem, which is one of the circuit-switched subsystem and the packet subsystem, to a transferring-in subsystem, which is another of the circuit-switched subsystem and the packet subsystem, wherein the centralized service control is maintained across the radio layer handover.

2. The method of claim 1 wherein the session signaling is anchored at a first function in the multimedia subsystem and a session signaling path extends to the user element through a control channel in the circuit-switched subsystem when the user element is served by the circuit-switched subsystem, and extends to the user element through the packet subsystem when the user element is served by the packet subsystem.

3. The method of claim 2 wherein:

a stateless remote user agent function is provided in the session signaling path in the circuit-switched subsystem and a stateful remote user agent function is provided in the session signaling path at the first function;

the stateless remote user agent and the stateful remote user agent represent the user element to the multimedia subsystem when the user element is served by the circuit-switched subsystem; and

the stateful remote user agent maintains service state information in the session signaling for the communication session across the radio layer handover.

5. The method of claim 2 wherein a stateful remote user agent function is provided in the session signaling path at the first function and maintains service state information in the session signaling for the communication session across the radio layer handover.

6. The method of claim 5 wherein the stateful remote user agent is the only remote user agent provided to represent the user element to the multimedia subsystem.

7. The method of claim 1 wherein the radio layer handover of the user element from the transferring-out subsystem to the transferring-in subsystem is effected before a bearer path in the transferring-in subsystem is established to a target access cell in the transferring-in subsystem.

8. The method of claim 1 further comprising delivering downlink traffic toward the user element over a first bearer path in the transferring-out subsystem and over a second bearer path in the transferring-in subsystem toward the user element in association with the radio layer handover, wherein the radio layer handover of the user element from the transferring-out subsystem to the transferring-in subsystem is effected after the second bearer path in the transferring-in subsystem is established to a target access cell in the transferring-in subsystem.

9. The method of claim 8 wherein delivery of the downlink traffic toward the user element over the first bearer path is stopped upon receiving uplink traffic from the user element over the second bearer path.

10. The method of claim 1 further comprising providing session updates toward the remote endpoint in association with the radio layer handover, wherein the session updates present communication information bearing on at least one of a group consisting of an address to which to direct bearer traffic and communication information associated with delivering the bearer traffic.

11. The method of claim 1 wherein effecting the radio layer handover comprises providing control of the radio layer handover from the multimedia subsystem.

12. The method of claim 1 wherein effecting the radio layer handover comprises:

to the transferring-out subsystem, representing a handover function as a target cell in a subsystem of the same type as the transferring-out subsystem;

to the transferring-in subsystem, representing the handover function as a source cell in a subsystem of the same type as the transferring-in subsystem; and

facilitating the radio layer handover from an access cell in the transferring-out subsystem to an access cell in the transferring-in subsystem.

13. The method of claim 12 wherein the session signaling is anchored at a first function in the multimedia subsystem and a session signaling path extends to the user element in the circuit-switched subsystem when the user element is served by the circuit-switched subsystem, wherein the handover function is provided in the session signaling path.

14. The method of claim 13 wherein a remote user agent representing the user element to the multimedia subsystem is provided in the session signaling path when the user element is served by the circuit-switched subsystem.

15. The method of claim 12 wherein when the transferring-in subsystem is the circuit-switched subsystem, and further comprising queuing session downlink signaling associated with a bearer path being established in the circuit-switched subsystem at the handover function until the user element transitions to the transferring-in subsystem.

16. The method of claim 12 wherein the session signaling path extends through a gateway interworking the multimedia subsystem with the packet subsystem, and further comprising providing a context update by the handover function to the gateway to inform the gateway of a transition of the communication session from the transferring-out subsystem to the transferring-in subsystem.

17. The method of claim 1 wherein the radio layer handover transfers wireless communication access from a source cell in the transferring-out subsystem to a target cell in the transferring-in subsystem, wherein the source cell supports wireless communications using one generation of wireless access technology and the target cell supports wireless communications using another generation of the wireless access technology.

18. The method of claim 1 wherein the packet subsystem supports Fourth Generation (4G) wireless access technology and the circuit-switched subsystem supports one of First, Second, and Third Generation (1×

, 2G, 3G) wireless access technologies.

4. The method of clam 3 wherein the stateless remote user agent does not maintain service state information for the communication session across the radio layer handover.

19. A system for facilitating inter-subsystem handovers between a circuit-switched subsystem and a packet subsystem while maintaining service control comprising:

at least one communication interface; and

a control system associated with the at least one communication interface and adapted to;

anchor session signaling for a communication session established between a user element and a remote endpoint in a multimedia subsystem; and

provide centralized service control for the communication session from the multimedia subsystem when the user element is served by the circuit-switched subsystem and when the user element is served by the packet subsystem, wherein during the communication session, the centralized service control is maintained across a radio layer handover of the user element from a transferring-out subsystem, which is one of the circuit-switched subsystem and the packet subsystem, to a transferring-in subsystem, which is another of the circuit-switched subsystem and the packet subsystem.

20. The system of claim 19 wherein the session signaling is anchored at a first function provided by the control system, and a session signaling path extends to the user element through a control channel in the circuit-switched subsystem when the user element is served by the circuit-switched subsystem and extends to the user element through the packet subsystem when the user element is served by the packet subsystem.

21. The system of claim 20 wherein:

a stateless remote user agent function is provided in the session signaling path in the circuit-switched subsystem and a stateful remote user agent function is provided in the session signaling path by the first function;

the stateless remote user agent and the stateful remote user agent represent the user element to the multimedia subsystem when the user element is served by the circuit-switched subsystem; and

the stateful remote user agent maintains service state information in the session signaling for the communication session across the radio layer handover.

23. The system of claim 20 wherein a stateful remote user agent function is provided in the session signaling path by the first function and maintains service state information in the session signaling for the communication session across the radio layer handover.

24. The system of claim 19 wherein the radio layer handover of the user element from the transferring-out subsystem to the transferring-in subsystem is effected before a bearer path in the transferring-in subsystem is established to a target access cell in the transferring-in subsystem.

25. The system of claim 19 further comprising a bi-cast node adapted to deliver downlink traffic toward the user element over a first bearer path in the transferring-out subsystem and over a second bearer path in the transferring-in subsystem toward the user element in association with the radio layer handover, wherein the radio layer handover of the user element from the transferring-out subsystem to the transferring-in subsystem is effected after the second bearer path in the transferring-in subsystem is established to a target access cell in the transferring-in subsystem.

26. The system of claim 25 wherein delivery of the downlink traffic toward the user element over the first bearer path is stopped upon receiving uplink traffic from the user element over the second bearer path.

27. The system of claim 19 further comprising a domain transfer function adapted to provide session updates toward the remote endpoint in association with the radio layer handover, wherein the session updates present communication information bearing on at least one of a group consisting of an address to which to direct bearer traffic and communication information associated with delivering the bearer traffic.

28. The system of claim 19 wherein effecting the radio layer handover comprises providing control of the radio layer handover from the multimedia subsystem.

29. The system of claim 19 further comprising a handover node, wherein to effect the radio layer handover, the handover node is adapted to:

represent a target cell in a subsystem of the same type as the transferring-out subsystem to the transferring-out subsystem;

represent a source cell in a subsystem of the same type as the transferring-in subsystem to the transferring-in subsystem; and

facilitate the radio layer handover from an access cell in the transferring-out subsystem to an access cell in the transferring-in subsystem.

30. The system of claim 29 wherein the session signaling is anchored at a first function in the multimedia subsystem and a session signaling path extends to the user element in the circuit-switched subsystem when the user element is served by the circuit-switched subsystem, wherein the handover function is provided in the session signaling path.

31. The system of claim 30 wherein a remote user agent representing the user element to the multimedia subsystem is provided in the session signaling path when the user element is served by the circuit-switched subsystem.

32. The system of claim 29 wherein when the transferring-in subsystem is the circuit-switched subsystem, the handover node is adapted to queue session downlink signaling associated with a bearer path being established in the circuit-switched subsystem at the handover function until the user element transitions to the transferring-in subsystem.

33. The system of claim 29 wherein the session signaling path extends through a gateway interworking the multimedia subsystem with the packet subsystem and the handover node is further adapted to provide a context update to the gateway to inform the gateway of a transition of the communication session from the transferring-out subsystem to the transferring-in subsystem.

34. The system of claim 19 wherein the radio layer handover transfers wireless communication access from a source cell in the transferring-out subsystem to a target cell in the transferring-in subsystem, wherein the source cell supports wireless communications using one generation of wireless access technology and the target cell supports wireless communications using another generation of the wireless access technology.

35. The system of claim 19 wherein the packet subsystem supports Fourth Generation (4G) wireless access technology and the circuit-switched subsystem supports one of First, Second, and Third Generation (1×

, 2G, 3G) wireless access technologies.

22. The system of clam 21 wherein the stateless remote user agent does not maintain service state information for the communication session across the radio layer handover.