Method and apparatus for inter-system active handoff of a hybrid subscriber unit

• US 20060109819A1
• Filed: 11/18/2005
• Published: 05/25/2006
• Est. Priority Date: 11/22/2004
• Status: Abandoned Application

• Current Assignee: Motorola, Inc. (Motorola Solutions, Inc.)
• Original Assignee: Motorola, Inc. (Motorola Solutions, Inc.)
• Inventors: Balasuriya, Senaka, Marin, James S.
• Application Number:
  US11/282,918
• Publication Number:
  US 20060109819A1
• Time in Patent Office: Days
• US Class Current: 370/331
• CPC Class Codes: H04L 12/18 for broadcast or conference , e.g. multicast
• CPC Class Codes: H04L 2012/6424 Access arrangements
• CPC Class Codes: H04L 65/1101 Session protocols
• CPC Class Codes: H04L 65/1104 Session initiation protocol [SIP]
• CPC Class Codes: H04W 36/026 Multicasting of data during hand-off
• CPC Class Codes: H04W 36/1446 wherein at least one of the networks is unlicensed
• CPC Class Codes: H04W 40/02 Communication route or path selection, e.g. power-based or shortest path routing
• CPC Class Codes: H04W 88/06 adapted for operation in multiple networks or having at least two operational modes, e.g. multi-mode terminals

Abstract

A communication system provides for an active handoff of a voice call between a packet switched network and a circuit switched network. An active handoff from the packet switched network to the circuit switched network is accomplished by multicasting the call over forward links of both networks during the handoff. An active handoff from the circuit switched network to the packet switched network is accomplished by multicasting the call over reverse links of both networks during the handoff. The former handoff further may be facilitated by routing the call for each network through a same packet data control switch, and the latter handoff further may be facilitated by routing the call for each network through a same mobile switching center. In order for a subscriber unit to operate concurrently in both networks, the subscriber unit may comprise multiple transceivers or a single transceiver that is rapidly switched between the networks.

Claims

1. A method for handoff of a voice call from a packet switched network having a packet data control switch to a circuit switched network, the method comprising:

conveying forward link voice traffic to, and receiving reverse link voice traffic from, a subscriber unit via the packet switched network;

receiving, by the packet switched network, a notification to hand off the call to the circuit switched network;

in response to receiving the handoff notification, conveying forward link voice traffic to the subscriber unit via the packet switched network and via the packet data control switch and the circuit switched network, and concurrently receiving reverse link voice traffic only via the packet switched network;

when conveying forward link voice traffic to the subscriber unit via each of the packet switched network and the circuit switched network, switching from the packet switched network to the packet data control switch and the circuit switched network for reception of reverse link voice traffic; and

in response to switching from the packet switched network to the circuit switched network for reception of reverse link voice traffic, ceasing conveying forward link voice traffic to the subscriber unit via the packet data control switch and the packet switched network while continuing to convey forward link voice traffic to the subscriber unit via the packet data control switch and the circuit switched network.

2. The method of claim 1, wherein conveying forward link voice traffic to the subscriber unit via both the packet switched network and the circuit switched network comprises conveying, by the packet data control switch, forward link voice traffic to the subscriber unit via both the packet switched network and the circuit switched network

3. The method of claim 2, wherein receiving a notification to hand off the call from the packet switched network to the circuit switched network comprises receiving, by the packet data control switch from the subscriber unit, a message identifying the circuit switched network as a target of the handoff and wherein conveying forward link voice traffic to the subscriber unit via both the packet switched network and the circuit switched network comprises, conveying, by the packet data control switch based on the message identifying the circuit switched network, forward link voice traffic to the subscriber unit via both the packet switched network and the circuit switched network.

4. The method of claim 3, wherein the message identifying the circuit switched network as a target of the handoff comprises a Session Initiation Protocol message.

5. The method of claim 1, wherein the notification to hand off the call from the packet switched network to the circuit switched network identifies the circuit switched network as a target of a handoff and wherein conveying forward link voice traffic to the subscriber unit via both the packet switched network and the circuit switched network comprises:

notifying the circuit switched network, by the packet switched network, of the need for a handoff of the subscriber unit; and

in response to the notification of the circuit switched network, establishing a bearer path between the circuit switched network and the subscriber unit and conveying forward link voice traffic to the subscriber unit via the established bearer path.

6. The method of claim 5, wherein notifying the circuit switched network of the need for a handoff of the subscriber unit comprises conveying a TIA-41 FACDIR2 INVOKE message to the circuit switched network.

7. The method of claim 5, further comprising acknowledging the notification of the circuit switched network.

8. The method of claim 5, wherein establishing a bearer path between the circuit switched network and the subscriber unit comprises, in response to notification of the circuit switched network of the need for a handoff:

conveying, by the circuit switched network to the subscriber unit, a handoff request message; and

in response to conveying the handoff request message, establishing a bearer path between the circuit switched network and the subscriber unit.

9. The method of claim 1, wherein switching reception of reverse link voice traffic from the packet switched network to the circuit switched network comprises:

informing the subscriber unit that the handoff is preceding; and

in response to informing the subscriber unit that the handoff is preceding, switching reception of reverse link voice traffic from the packet data control switch and the packet switched network to the packet data control switch and circuit switched network.

10. The method of claim 9, further comprising:

receiving, by the circuit switched network from the subscriber unit, notification that the handoff is complete; and

informing, by the circuit switched network of the packet switched network, that the subscriber unit has completed the handoff.

11. The method of claim 9, wherein ceasing conveying forward link frames to the subscriber unit via the packet switched network comprises:

receiving, by the packet switched network from the subscriber unit, notification that the handoff is complete; and

in response to receiving notification that the handoff is complete, ceasing conveyance of forward link voice traffic to the subscriber unit via the packet data control switch and the packet switched network while continuing to convey forward link voice traffic to the subscriber unit via the packet data control switch and the circuit switched network.

12. A packet data control switch having a processor configured to, in association with a subscriber unit call, route forward link voice traffic and receive reverse link voice traffic via a packet switched network, receive a notification to hand off the call from the packet switched network to a circuit switched network, in response to receiving the handoff notification, route forward link voice traffic to the subscriber unit via both the packet switched network and the circuit switched network and concurrently receive reverse link voice traffic only via the packet switched network, when conveying forward link voice traffic to the subscriber unit via each of the packet switched network and the circuit switched network, switch reception of reverse link voice traffic from the packet switched network to the circuit switched network, and in response to switching reception of reverse link voice traffic from the packet switched network to the circuit switched network, cease routing forward link voice traffic to the subscriber unit via the packet switched network while continuing to route forward link voice traffic to the subscriber unit via the circuit switched network.

13. The packet data control switch of claim 12, wherein the notification comprises a Session Initiation Protocol message that identifies the circuit switched network as a target of the handoff.

14. The packet data control switch of claim 12, wherein the notification that the call should be handed off identifies the circuit switched network as a target of the handoff and wherein, in response to receiving the notification, the processor notifies the circuit switched network of the need for a handoff of the subscriber unit.

15. The packet data control switch of claim 14, wherein the processor notifies the circuit switched network of the need for a handoff of the subscriber unit by conveying a TIA-41 FACDIR2 INVOKE message to the circuit switched network.

16. The packet data control switch of claim 14, wherein the processor further receives an acknowledgement of the notification of the circuit switched network.

17. The packet data control switch of claim 12, wherein the processor switches receiving reverse link frames from the packet switched network to the circuit switched network by informing the subscriber unit that the handoff is preceding and, in response to informing the subscriber unit that the handoff is preceding, receives reverse link voice traffic from the subscriber unit via the circuit switched network instead of the packet switched network.

18. The packet data control switch of claim 17, wherein the processor further is informed by the circuit switched network that the subscriber unit has completed the handoff.

19. The packet data control switch of claim 17, wherein the processor ceases conveying forward link voice traffic to the subscriber unit via the packet switched network by receiving from the subscriber unit notification that the handoff is complete and, in response to receiving notification that the handoff is complete, ceasing conveying forward link voice traffic to the subscriber unit via the packet switched network.

20-33. -33. (canceled)

34. A method for handoff of a voice call from a packet switched network having a packet data control switch to a circuit switched network, the method comprising:

communicating voice traffic via the packet switched network;

receiving, by the packet switched network, a notification to hand off the call, wherein the notification to hand off identifies the circuit switched network as the network to hand off the call to; and

in response to receiving the handoff notification, establishing communication via the circuit switched network and terminating communication via the packet switched network.

35. The method of claim 34, wherein the step of establishing communication via the circuit switched network includes paging the subscriber unit via the circuit switched network and receiving a response to the page message from the subscriber unit.

36. A method for handoff of a voice call from a packet switched network having a packet data control switch to a circuit switched network, the method comprising:

communicating voice traffic via the packet switched network;

determining, by a subscriber unit, to hand off the call;

transmitting a notification to hand off the call, wherein the notification to hand off identifies the circuit switched network as the network to hand off the call to; and

in response to transmitting the handoff notification, establishing communication via the circuit switched network and terminating communication via the packet switched network.

37. The method of claim 36, wherein the step of establishing communication via the circuit switched network includes receiving a paging message at the subscriber unit via the circuit switched network and transmitting a response to the page message from the subscriber unit.

38-41. -41. (canceled)