Multiplex communications – Pathfinding or routing – Combined circuit switching and packet switching
Reexamination Certificate
1999-12-10
2004-08-03
Hsu, Alpus H. (Department: 2665)
Multiplex communications
Pathfinding or routing
Combined circuit switching and packet switching
C370S389000, C370S525000, C370S526000, C379S088170, C379S418000
Reexamination Certificate
active
06771641
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates generally to telecommunication systems, and more particularly, to a system and method for collecting and transporting dual tone multi-frequency (“DTMF”) digits through a packet network.
Packet networks are often preferred over traditional circuit-switched communication networks because they provide speed, flexibility and efficiency for data communication. However, much of the hardware equipment currently in existence is designed for the circuit-switched communication networks such as the public switched telephone network (“PSTN”). The coexistence of both types of networks creates many gaps between the technologies. Traditionally, a voice conversation and DTMF digits are transported together over the PSTN through a voice channel. Because the comparatively slow speed of traditional communication technology, the DTMF digits will be well preserved.
DTMF digits are not always well preserved in a high speed packet network. Packet networks compress and embed information into small and numerous packets, and send the packets out with the expectation that all these packets will be appropriately received by another end point and assembled accordingly. However, it is inevitable that some information may not be recoverable by the receiving end point and thus lost in between the two end points. This is especially true when transferring DTMF digits in a voice channel over a packet network. Since a DTMF digit bears information of a relatively small size, it is more likely that the receiving end point cannot assemble packets to obtain a full comprehension of the sent tone.
Therefore, what is needed is a system and method for collecting and transporting DTMF digits over a channel independent of the voice channel in order to preserve the integrity of the DTMF digits.
SUMMARY OF THE INVENTION
A system and method is provided for collecting and transporting DTMF digits between two network end points in a packet network in order to preserve the integrity of the DTMF digits. In one embodiment, the present invention uses a Session Initiation Protocol (SIP), which is currently defined by the standard body of Internet Engineering Task Force. SIP applications are typically used to establish and terminate multimedia sessions and utilize certain predetermined messages, such as an INFO message, and templates. DTMF digits can be collected and transported by using SIP INFO messages. This works especially well for telephony applications which may require mid session signaling.
One embodiment of the present invention has an end point sending collected digits to another end point server directly without the use of any predetermined SIP template.
In another embodiment of the present invention, a first end point sends a template to a second end point to request digit collection. The second end point collects certain number of digits based on the format defined by the received template, and sends the collected digits to the first end point.
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Choudhuri Tahsin
Haun Christopher
Orton Scott L.
Sollee Patrick
Whynot Stephen
Haynes and Boone LLP
Hsu Alpus H.
Molinari Michael J
Nortel Networks Limited
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