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

• US 20060111115A1
• Filed: 11/18/2005
• Published: 05/25/2006
• Est. Priority Date: 11/22/2004
• Status: Active Grant

• Current Assignee: Google Technology Holdings LLC (Alphabet Inc.)
• Original Assignee: Motorola Mobility, Inc. (Lenovo Group Ltd.)
• Inventors: Balasuriya, Senaka, Marin, James S.
• Granted Patent: US 7,697,480 B2
• Time in Patent Office: Days
• US Class Current: 455/442
• CPC Class Codes: H04W 36/026 Multicasting of data during hand-off
• CPC Class Codes: H04W 36/14 Reselecting a network or an air interface
• CPC Class Codes: H04W 36/1446 wherein at least one of the networks is unlicensed

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

1-19. -19. (canceled)

20. A method for inter-network handoff of a voice call from a circuit switched network to a packet switched network, the method comprising:

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

determining, by the circuit switched network, to hand off the call;

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

in response to receiving the handoff notification, conveying, by the packet switched network of the subscriber unit, a request to perform a handoff and establishing a communication session between the packet switched network and the subscriber unit;

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

when receiving reverse link voice traffic via the packet switched network and the circuit switched network, switching from the circuit switched network to the packet switched network for conveyance of forward link voice traffic to the subscriber unit; and

in response to switching forward link voice traffic from the packet switched network to the circuit switched network, reception of reverse link voice traffic via the circuit switched network while continuing to receive reverse link voice traffic via the packet switched network.

21. The method of claim 20, wherein the circuit switched network notifies the packet switched network of the need for a handoff by conveying a TIA-41 FACDIR2 INVOKE message to the packet switched network.

22. The method of claim 20, wherein establishing a communication session between the packet switched network and the subscriber unit comprises:

establishing a Point-to-Point Protocol communication session with the subscriber unit; and

establishing a bearer path between the packet switched network and the subscriber unit.

23. The method of claim 22, wherein receiving reverse link voice traffic from the subscriber unit via tide circuit switched network and via the packet switched network comprises receiving reverse link tames comprising voice traffic from the subscriber unit via the established bearer path between the packet switched network and the subscriber unit.

24. The method of claim 20, further comprising:

establishing a bearer path between the packet switched network and the subscriber unit;

in response to establishing the bearer path between the packet switched network and the subscriber unit, conveying a handoff notification by the packet switched network to the circuit switched network; and

wherein the conveyance of forward link voice traffic to the subscriber unit is switched from the circuit switched network to the packet switched network in response to the conveyance of the handoff notification by the packet switched network to the circuit switched network.

25. The method of claim 24, wherein the handoff notification conveyed by the packet switched network to the circuit switched network comprises a TIA-41 FACDIR2 RESPONSE message.

26. The method of claim 24, wherein the circuit switched network comprises a mobile switching center and wherein switching from the circuit switched network to the packet switched network for conveyance of forward link voice traffic to the subscriber unit comprises switching from the mobile switching center and the circuit switched network to the mobile switching center and the packet switched network for conveyance of forward link voice traffic.

27. The method of claim 20, wherein ceasing reception of reverse link voice traffic via the circuit switched network comprises:

instructing the subscriber unit, by the circuit switched network, to cease conveying reverse link voice traffic to the circuit switched network; and

in response to conveying the instruction, ceasing reception of reverse link voice traffic by the circuit switched network.

28. The method of claim 27, further comprising:

receiving, by the packet switched network from the subscriber unit, information that the request to perform a handoff has been successfully executed;

in response to being informed that that the request to perform a handoff has been successfully executed, informing the circuit switched network, by the packet switched network, that the packet switched network is engaged in a bi-directional exchange of voice traffic with the subscriber unit; and

in response to being informed that the packet switched network is engaged in a bi-directional exchange of voice traffic with the subscriber unit, terminating the circuit switched network call.

29. The method of claim 20, further comprising receiving, by the circuit switched network, notification that the handoff is completed.

30. A communication system that provides for inter-network handoff of a voice call from a circuit switched network to a packet switched network, the system comprising:

a base station that transmits forward link voice traffic to a subscriber unit via a first forward link, receives reverse link voice traffic from the subscriber unit via a first reverse link from, and that determines to hand off the call;

a mobile switching center in communication with the base station that conveys the forward link voice traffic to the base station, receives the reverse link voice traffic from the base station, and that, in response to the determination to hand off the call, conveys a notification of the need for a handoff;

a packet data control switch that receives the handoff notification from the mobile switching center and, in response to receiving the handoff notification, requests that the subscriber unit perform a handoff;

an access network in communication with the packet data control switch that, in response to the request to perform a handoff, establishes a second forward link and a second reverse link with the subscriber unit; and

wherein, in response to the establishment of the second forward link and the second reverse link with the subscriber unit, each of the base station and the access network receives reverse link voice traffic from the subscriber unit while only the base station conveys forward link voice traffic to the subscriber unit, wherein after each of the base station and the access network begins receiving reverse link voice traffic from the subscriber unit, conveyance of the forward link voice traffic to the subscriber unit is switched from the base station and the first forward link to the access network and the second forward link, and wherein, in response to switching conveyance of forward link voice traffic from the base station and the first forward link to the access network and the second forward link, the base station ceases receiving reverse link voice traffic while the access network continues to receive reverse link voice traffic.

31. The system of claim 30, wherein the mobile switching center notifies the packet data control switch of the need for a handoff by conveying a TIA-41 FACDIR2 INVOKE message to the packet data control switch.

32. The system of claim 30, wherein the packet data control switch, in response to the establishment of the second forward link and the second reverse link with the subscriber unit, conveys a handoff notification to the mobile switching center and wherein the mobile switching center, in response to receiving the handoff notification from the packet data control switch, switches the forward link voice traffic from the base station and the first forward link to the access network and the second forward link.

33. The system of claim 32, wherein the handoff notification conveyed by the packet data control switch to the mobile switching center comprises a TIA-41 FACDIR2 RESPONSE message.

34-41. -41. (canceled)