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 based on the determined differential delay 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.
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Citations
20 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:
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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 based on the determined differential delay and then terminating the first voice path. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. A telephone enabled mobile electronic device comprising:
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a wireless wide area network (WAN) communications subsystem for exchanging voice data with a wireless wide are 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;
a phone interface for receiving data from the microphone and converting the microphone data into digital voice data and for receiving digital voice data for the speaker and converting the digital voice data into data for output by the speaker; and
a handoff synchronizer connected to the phone interface, the WAN communications subsystem and the WLAN communications subsystem for synchronizing a handoff of an in-progress voice call between the mobile device and a terminal end point, the handoff synchronizer including;
(i) comparator means for comparing streams of voice data received simultaneously by the WAN communications subsystem and the WLAN communications subsystem and determining a transmission delay differential between the streams of voice data; and
(ii) timing adjustment means responsive to the comparator means for adjusting the timing of at least one of the streams of voice data based on the determined delay differential. - View Dependent Claims (11, 12, 13, 14, 15)
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16. 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 for exchanging data with wireless access points in the WLAN 112;
a first gateway for exchanging data with the WAN through a communications link;
a second gateway for exchanging data with a terminal end point over a further communications link; and
a handoff synchronizer connected to the second gateway, the access point interface and the first gateway for synchronizing 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) comparator means for comparing a stream of voice data from the mobile device received through the AP Interface and a stream of voice data from the mobile device received through the first gateway and determining a transmission delay differential between the streams of voice data;
(ii) timing adjustment means responsive to the comparator means for adjusting the timing of at least one of the streams of voice data based on the determined delay differential; and
(iii) switch means for disconnecting the second gateway from one of the AP interface and the first gateway and connecting the second gateway to the other one of the AP interface and the first gateway upon completion of the timing adjustment. - View Dependent Claims (17, 18, 19, 20)
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Specification