Voice synchronization during call handoff
First Claim
1. A method for handing off an in-progress call in a communications system that comprises a wireless wide area network (WAN) and a wireless local area network (WLAN) having at least partially overlapping coverage areas, a mobile device having a WAN communications subsystem for exchanging wireless voice data with the WAN and a WLAN communications subsystem for exchanging wireless voice data with the WLAN, wherein prior to handoff a communications path between the mobile device and a remote location Comprises a first voice path through one of the WAN and the WLAN,the handoff method comprising:
- establishing a second voice path between the mobile device and the remote location through the other one of the WAN and the WLAN;
transmitting in parallel streams of identical voice data over the first and second voice paths;
comparing the streams of voice data after they have been transmitted through the first and second voice paths to determine a differential delay in transmission times between the first and second paths; and
synchronizing the parallel streams of voice data by adjusting the timing of at least one of the streams of voice data until the determined differential delay reaches a predetermined threshold and then terminating the first voice path.
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Accused Products
Abstract
A method, mobile electronic device and system for synchronizing hand-off of a voice media session between a WAN/cellular network and a WLAN network. When a hand-off occurs, the connection with both networks is temporarily maintained and the voice data on both connections compared to determine differences in the delays experienced over both connections. The timing of one or both voice streams is adjusted to synchronize the voice streams, and then the handoff is completed.
21 Citations
17 Claims
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1. A method for handing off an in-progress call in a communications system that comprises a wireless wide area network (WAN) and a wireless local area network (WLAN) having at least partially overlapping coverage areas, a mobile device having a WAN communications subsystem for exchanging wireless voice data with the WAN and a WLAN communications subsystem for exchanging wireless voice data with the WLAN, wherein prior to handoff a communications path between the mobile device and a remote location Comprises a first voice path through one of the WAN and the WLAN,
the handoff method comprising: -
establishing a second voice path between the mobile device and the remote location through the other one of the WAN and the WLAN; transmitting in parallel streams of identical voice data over the first and second voice paths; comparing the streams of voice data after they have been transmitted through the first and second voice paths to determine a differential delay in transmission times between the first and second paths; and synchronizing the parallel streams of voice data by adjusting the timing of at least one of the streams of voice data until the determined differential delay reaches a predetermined threshold and then terminating the first voice path. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. A mobile electronic device comprising
a wireless wide area network (WAN) communications subsystem for exchanging voice data with a wireless wide area network (WAN); -
a wireless local area network (WLAN) communications subsystem for exchanging voice data with a wireless local area network (WLAN); a speaker; a microphone; an interface adapted to; receive microphone data from the microphone; convert the microphone data into microphone digital voice data; receive speaker digital voice data for the speaker; and convert the speaker digital voice data into data for output by the speaker; and a handoff synchronizer connected to the interface, the WAN communications subsystem and the WLAN communications subsystem the handoff synchronizer adapted to synchronize a handoff of an in-progress voice call between the mobile device and a terminal end point, the handoff synchronizer including; (i) a comparator module adapted to compare streams of voice data received simultaneously by the WAN communications subsystem and the WLAN communications subsystem; and determine a transmission delay differential between the streams of voice data; and (ii) a timing adjustment module, responsive to the comparator module, adapted to; adjust the timing of at least one of the streams of voice data until the comparator module determines that the determined transmission delay differential reaches a predetermined threshold. - View Dependent Claims (10, 11, 12, 13)
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14. A synchronizing handoff system for handing off in-progress voice call between a wireless wide area network (WAN) and a wireless local area network (WLAN), the system including:
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a WLAN access point interface adapted to exchange data with wireless access points in the WLAN; a first gateway adapted to exchange data with the WAN through a communications link; a second gateway adapted to exchange data with a terminal end point over a further communications link; and a handoff synchronizer connected to the second gateway, the WLAN access point interface and the first gateway the handoff synchronizer adapted to synchronize a handoff of an in-progress voice call in which a communications path is established between a mobile device and a terminal end point, the handoff synchronizer including; (i) a comparator module adapted to; compare a stream of voice data from the mobile device received through the WLAN access point interface and a stream of voice data from the mobile device received through the first gateway; and determine a transmission delay differential between the streams of voice data; (ii) a timing adjustment means module, responsive to the comparator module, adapted to adjust the timing of at least one of the streams of voice data until the comparator module determines that the determined transmission delay differential reaches a predetermined threshold; and (iii) a switch module adapted to disconnect the second gateway from one of the WLAN access point interface and the first gateway and connect the second gateway to the other one of the WLAN access point interface and the first gateway upon being caused to do so by the comparator module. - View Dependent Claims (15, 16, 17)
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Specification