Distributed conferencing system utilizing data networks

• US 6,466,550 B1
• Filed: 11/11/1998
• Issued: 10/15/2002
• Est. Priority Date: 11/11/1998
• Status: Expired due to Term

• Current Assignee: Cisco Technology, Inc. (Cisco Systems, Inc.)
• Original Assignee: Cisco Technology, Inc. (Cisco Systems, Inc.)
• Inventors: FitzGerald, Cary W., Foster, William R.
• Primary Examiner(s): Kizou, Hassan
• Assistant Examiner(s): SPAFFORD, TIMOTHY J
• Application Number:
  US09/190,034
• Time in Patent Office: 1,434 Days
• Field of Search: 370/260, 370/261, 370/266, 370/267, 370/268, 370/270, 379/201.01, 379/201.02, 379/202.01, 379/205.01
• US Class Current: 370/261
• CPC Class Codes: H04L 12/1813 for computer conferences, e.g. chat rooms instant messaging H04L51/04; protocols for multimedia communication H04L65/1101; arrangements for multi-party communication H04L65/403; telephonic conference arrangements H04M3/56; television conference systems H04N7/15
• CPC Class Codes: H04M 3/56 Arrangements for connecting several subscribers to a common circuit, i.e. affording conference facilities video conference systems H04N7/15
• CPC Class Codes: H04M 3/562 where the conference facilities are distributed
• CPC Class Codes: H04M 3/569 using the instant speaker's algorithm speech detection per se G10L25/78
• CPC Class Codes: H04M 7/006 Networks other than PSTN/ISDN providing telephone service, e.g. Voice over Internet Protocol (VoIP) , including next generation networks with a packet-switched transport layer H04L65/00 takes precedence; aspects not specific to the type of network H04M3/00; special services in those networks H04M3/42

Abstract

A distributed packet-based audio conferencing system, method for packet-based audio conferencing, and a transceiver for use in such conferencing are disclosed. The system uses a collection of transceivers, with each conference participant connected to a local transceiver. When a participant speaks, the local transceiver is responsible for relaying the speaker'"'"'s voice over a packet network by multicast transmission to transceivers local to each other conference participant. If multiple participants speak simultaneously, a multicast talk stream may originate from each speaker'"'"'s local transceiver. The total number of simultaneous speakers, however, is limited by an arbitration function resident in each transceiver.

The system reduces the costs associated with an always-up communication system. Compared to a data network solution employing a centralized bridge, the present conferencing system enjoys lower delay, lower bandwidth requirements, the ability to utilize voice compression throughout, and ease of reconfiguration.

Claims

1. A distributed conferencing system comprising:

multiple conferencing transceivers that communicate audio conference data to each other over a packet data network using a shared multicast group address, each transceiver comprising;

a bi-directional conference local data interface connected to at least one local conferencing point;

a bidirectional conference remote packet data interface connected to said packet data network;

a first data flow path from said local data interface to said remote packet data interface and a second data flow path from said remote packet data interface to said local data interface;

a switch inserted in said first data flow path; and

an arbitrator that monitors source attributes of conference data appearing at each of said interfaces and opens said switch when the number of contemporaneously received sources of conference data exceeds a preset maximum and the source attributes of conference data appearing at said remote packet data interface take precedence over the source attributes of conference data appearing at said local data interface.

2. The distributed conferencing system of claim 1, wherein the conferencing data originating at each of the multiple conferencing transceivers are assigned unique source values and the arbitrator determines which conferencing data takes precedence according to the assigned source values.

3. The distributed conferencing system of claim 2 wherein the source values are randomly generated numbers.

4. The distributed conferencing system of claim 1, wherein each of transceivers periodically transmits control packets containing a canonical name associated with their local conferencing point to the others of said transceivers, and wherein said arbitrator bases its source precedence decision on a stored precedence of canonical names.

5. The distributed conferencing system of claim 1, further comprising a bridge circuit connecting at least two local conferencing points to the bi-directional conference local data interface of one of said conferencing transceivers.

6. The distributed conferencing system of claim 1, further comprising at least one conferencing receiver that receives audio conference data from said conferencing transceivers over said packet data network using said shared multicast group address, said receiver connected to a receive-only conference point.

7. The distributed conferencing system of claim 1, wherein said transceivers also communicate video conference data packets, associated with said audio conference data packets, to each other over said packet data network using said shared multicast group address.

8. A distributed conferencing system comprising:

multiple conferencing transceivers that each communicate their local audio conference data stream to each of the other transceivers over a packet data network using a shared multicast group address, each transceiver having an arbitrator that monitors source values uniquely associated with each local and remote audio conference data stream received by the transceiver and independently limits active data streams based on those source values.

47. A distributed conferencing system according to claim 8 wherein each source value is a randomly generated number that uniquely identifies the associated data stream.

9. An audio conferencing transceiver comprising:

a bi-directional conference local data interface;

a bi-directional conference remote packet data interface;

a first data flow path from said local data interface to said remote packet data interface and a second data flow path from said remote packet data interface to said local data interface;

a switch inserted in said first data flow path; and

an arbitrator that monitors source attributes of conference data appearing at each of said interfaces and opens said switch when the number of sources of conference data exceeds a preset maximum and the source attributes of conference data appearing at said remote packet data interface take precedence over the source attributes of conference data appearing at said local data interface.

10. The audio conferencing transceiver of claim 9, wherein said local data interface is a packet data interface.

11. The audio conferencing transceiver of claim 10, wherein said local data interface and said packet data interface share a common physical network connection.

12. The audio conferencing transceiver of claim 9, wherein said first data flow path further comprises a speech encoder and a packetizer, and wherein said second data flow path comprises a depacketizer, a data buffer, and a speech decoder.

13. The audio conferencing transceiver of claim 12, wherein said local data interface is a pulse-code-modulated digital data interface.

14. The audio conferencing transceiver of claim 12, wherein said local data interface is an analog audio interface.

15. The audio conferencing transceiver of claim 14, further comprising a microphone and a speaker connected to said analog audio interface.

16. The audio conferencing transceiver of claim 9, wherein said second data flow path comprises an input selector in communication with said arbitrator, said input selector removing from said second data flow path packets corresponding to one or more sources of conference data when so instructed by said arbitrator.

17. The audio conferencing transceiver of claim 9, wherein said first data flow path further comprises a serial speech encoder and packetizer, and wherein said second data flow path further comprises a first serial depacketizer, data buffer, and speech decoder.

18. The audio conferencing transceiver of claim 17, wherein said second data flow path further comprises

a second serial depacketizer, data buffer, and speech decoder in parallel with said first serial depacketizer, data buffer, and speech decoder, and

a mixer connected to said first and second speech decoders.

19. The audio conferencing transceiver of claim 18, further comprising a local side-tone path from said first data flow path to said mixer.

20. The audio conferencing transceiver of claim 19, wherein said local side-tone path is switched by said arbitrator.

21. The audio conferencing transceiver of claim 18, further comprising a signal path from said input selector to said data buffer allowing said input selector to flush data from said data buffer corresponding to an identified data source.

22. The audio conferencing transceiver of claim 9, further comprising a local side-tone path from said first data flow path to said second data flow path.

23. The audio conferencing transceiver of claim 22, wherein said local side-tone path is switched by said arbitrator.

24. The audio conferencing transceiver of claim 9, wherein said transceiver resides within a packet data voice gateway.

25. A method for packet data conferencing between multiple remote conference participants comprising the steps of:

transmitting each remote conference participant'"'"'s voice to other remote conference participants by transmitting a transmit packet data talk stream from a transceiver local to that conference participant to a multicast group address;

receiving, at each said transceiver local to a remote conference participant, receive packet data talk streams from other remote conference participants sent to said multicast group address;

ranking, at each said transceiver, that transceiver'"'"'s transmit packet data talk stream source against each receive packet data talk stream source; and

inhibiting said transmitting step at one of said transceivers when the total number of packet data talk streams sensed by that transceiver exceeds a preset maximum and the transmit packet data talk stream source ranks lowest in said ranking step.

26. The method of claim 25, further comprising assigning each transceiver a unique identifier and attaching this identifier to each packet in that transceiver'"'"'s transmit packet data talk stream.

27. The method of claim 26, wherein said ranking step comprises numerically ranking said identifiers in a preset order.

28. The method of claim 27, wherein said unique identifiers are assigned randomly.

29. The method of claim 28, wherein said packet data talk streams utilize the Real-time Transport Protocol, and wherein said identifier comprises the synchronization source identifier of the Real-time Transport Protocol packet header.

30. The method of claim 25, further comprising attaching a timestamp to each packet in each packet data talk stream.

31. The method of claim 30, wherein said ranking step comprises ranking talk streams according to the first-received timestamp for each packet data talk stream.

32. The method of claim 25, further comprising identifying a packet data talk stream with a super-priority allowing it to win all said ranking.

33. The method of claim 25, further comprising discarding, at each said transceiver, a receive packet data talk stream when the total number of packet data talk streams sensed by that transceiver exceeds a preset maximum and that receive packet data talk stream source ranks lowest in said ranking step.

34. The method of claim 33, wherein said ranking step compares each receive packet data talk stream source against each other receive packet data talk stream source.

35. The method of claim 25, wherein said inhibiting step always inhibits the transmit packet data talk stream regardless of ranking when, at the inception of voice activity by the transmitter'"'"'s local conference participant, the total number of received packet data talk streams sensed by that transceiver equals or exceeds said preset maximum.

36. The method of claim 25, wherein said inhibiting step is disabled for an active transmit packet data talk stream a preset time after the inception of voice activity by the transmitter'"'"'s local conference participant.

37. The method of claim 36, wherein said preset time is an estimated worse-case round trip delay for a conference.

38. A method for operating an audio conferencing transceiver comprising the steps of:

receiving multicast audio conferencing packets at a remote packet data interface;

receiving unicast audio conferencing packets at a local packet data interface;

monitoring both the source attributes of conferencing packets appearing at each of said interfaces and the number of concurrent sources of conference packets; and

multicast transmitting said unicast audio conferencing packets through said remote packet data interface unless the number of concurrent sources of conference data exceeds a preset maximum and the source attributes of said multicast audio conferencing packets take precedence over the source attributes of said unicast data packets.

39. The method of claim 38, further comprising the step of unicast transmitting said multicast audio conferencing packets through said local packet data interface.

40. The method of claim 39, wherein said unicast transmitting step occurs for each source of said multicast audio conferencing packets, unless the number of concurrent sources of conference data exceeds a preset maximum and the source attributes for that particular source of said multicast audio conferencing packets rank lower than the source attributes of other concurrent sources of audio conferencing packets.

41. A computer readable medium containing software for operating an audio conferencing transceiver, the software comprising:

code for receiving multicast audio conferencing packets at a remote packet data interface;

code for receiving unicast audio conferencing packets at a local packet data interface;

code for monitoring both the source attributes of conferencing packets appearing at each of said interfaces and the number of concurrent sources of conference packets; and

code for multicast transmitting said unicast audio conferencing packets through said remote packet data interface unless the number of concurrent sources of conference data exceeds a preset maximum and the source attributes of said multicast audio conferencing packets take precedence over the source attributes of said unicast data packets.

42. A computer readable medium according to claim 41, further including code for unicast transmitting said multicast audio conferencing packets through said local packet data interface.

43. A computer readable medium according to claim 42, wherein said code for unicast transmitting is performed for each source of said multicast audio conferencing packets, unless the number of concurrent sources of conference data exceeds a preset maximum and the source attributes for that particular source of said multicast audio conferencing packets rank lower than the source attributes of other concurrent sources of audio conferencing packets.

44. A system for operating an audio conferencing transceiver comprising:

means for receiving multicast audio conferencing packets at a remote packet data interface;

means for receiving unicast audio conferencing packets at a local packet data interface;

means for monitoring both the source attributes of conferencing packets appearing at each of said interfaces and the number of concurrent sources of conference packets; and

means for multicast transmitting said unicast audio conferencing packets through said remote packet data interface unless the number of concurrent sources of conference data exceeds a preset maximum and the source attributes of said multicast audio conferencing packets take precedence over the source attributes of said unicast data packets.

45. The system of claim 44 including means for unicast transmitting said multicast audio conferencing packets through said local packet data interface.

46. The system of claim 45, wherein said means for unicast transmitting occurs for each source of said multicast audio conferencing packets, unless the number of concurrent sources of conference data exceeds a preset maximum and the source attributes for that particular source of said multicast audio conferencing packets rank lower than the source attributes of other concurrent sources of audio conferencing packets.