Packet telephone scheduling with common time reference

• US 6,259,695 B1
• Filed: 07/28/1999
• Issued: 07/10/2001
• Est. Priority Date: 06/11/1998
• Status: Expired due to Fees

• Current Assignee: Synchrodyne Networks Incorporated
• Original Assignee: Synchrodyne Networks Incorporated
• Inventors: Ofek, Yoram
• Primary Examiner(s): Olms, Douglas
• Assistant Examiner(s): Pizarro, Ricardo M.
• Application Number:
  US09/362,335
• Time in Patent Office: 713 Days
• Field of Search: 370/395, 370/396, 370/397, 370/398, 370/399, 370/392, 370/498, 370/509, 370/517, 370/252, 370/253, 370/465, 370/503, 370/519, 370/353, 370/356, 370/389, 709/238
• US Class Current: 370/389
• CPC Class Codes: H04J 3/0644 External master-clock
• CPC Class Codes: H04J 3/0697 Synchronisation in a packet node
• CPC Class Codes: H04L 12/6418 Hybrid transport
• CPC Class Codes: H04L 47/10 Flow control; Congestion control
• CPC Class Codes: H04L 47/22 Traffic shaping
• CPC Class Codes: H04L 47/283 in response to processing delays, e.g. caused by jitter or round trip time [RTT]
• CPC Class Codes: H04L 47/43 Assembling or disassembling of packets, e.g. segmentation and reassembly [SAR]
• CPC Class Codes: H04L 49/90 Buffering arrangements
• CPC Class Codes: H04L 49/9023 for implementing a jitter-buffer
• CPC Class Codes: H04L 69/28 Timers or timing mechanisms used in protocols
• CPC Class Codes: H04L 9/40 Network security protocols

Abstract

The invention describes a method for interfacing a packet-switched network with real-time streams from various sources, such as circuit-switched telephony network sources. The network interfaces and gateways maintain a common time reference (CmR), which is obtained either from an external source (such as GPS—Global Positioning System) or is generated and distributed intemally. A data packet that is packetized at the gateway is scheduled to be forwarded to the network in a predfined time that is responsive to the common time reference. The invention relates, in particular, to timely forwarding and delivery of data packet between voice over IP (VoIP) gateways. Consequently, the invention provides a routing service between any two VoIP gateways where the end-to-end performance parameters, such as loss, delay and jitter, have deterministic guarantees. Furthermore, the invention enables gateway functions with minimum delay.

Claims

1. A gateway control system comprising:

a source of a common time reference signal;

a source of a steam of digital samples;

a packeting subsystem for providing packetization of a plurality of the digital samples into a data packet; and

a controller for defining a plurality of predefined time frames responsive to the common time reference signal, and for scheduling of transmission of associated respective ones of the data packets at respective selected ones of the predefined time frames;

wherein the packeting subsystem provides packetization responsive to the controller, and wherein the packetization of each of the respective ones of the data packets is scheduled for completion prior to the respective selected predefined time frame.

2. The gateway control system as in claim 1, wherein each respective one of the data packets is output from the gateway system during the respective selected predefined time frame.

3. The gateway control system as in claim 1, wherein, for each respective one of the data packets, the packetization of the plurality of the digtal samples into the data packets is completed immediately prior to the respective selected predefined time frames.

4. The gateway control system as in claim 1, wherein the time frames are scheduled and structured into a time cycle comprised of a fixed number of contiguous time frame positions which are structured into a stream of a plurality of contiguous time cycles.

5. The gateway control system as in claim 4, wherein the scheduling of transmission of respective data packets occurs at a defined one of the time frame positions within each of the time cycles.

6. The gateway control system as in claim 5, wherein the scheduling of transmission of respective data packets occurs at multiple defined ones of the time frame positions within each of the cycles.

7. The gateway control system as in claim 4,

wherein a fixed number of a plurality of contiguous ones of the time cycles comprise a super cycle, wherein the super cycle is periodic; and

wherein the scheduling of the transmission of respective data packets occurs at a defined one of the time frame positions periodically during at least one associated respective one of the time cycles during each of the super cycles.

8. The gateway control system as in claim 4,

wherein a fixed number of a plurality of contiguous ones of the time cycles comprise a super cycle, wherein the super cycle is periodic;

and

wherein the scheduling of transmission of respective data packets occurs at least at one of the defined time frame positions within each of the super cycles.

9. The gateway control system as in claim 1, wherein the common time reference signal is coupled from a GPS (Global Positioning System).

10. The gateway control system as in claim 1, wherein the common time reference signal is provided in accordance with the UTC (Coordinated Universal Time) standard.

11. The gateway control system as in claim 10, wherein the super cycle duration is equal to at least one of a predefined number of seconds and a predefined fraction of a second, as measured using the UTC standard.

12. The gateway control system as in claim 1, wherein the stra of digital samples are at least one of digitized analog voice telephony, digitized uncompressed voice telephony, digitized compressed voice telephony, narrowband Integrated Service Digital Networks (ISDN), video, television (TV), high definition TV (HDTV), and high fidelity (Hi-Fi) audio.

13. The gateway control system as in claim 1, wherein there are a plurality of streams of digital samples;

and

wherein the packeting subsystem provides for packetization of the data packets for each of the plurality of streams.

14. The gateway control system as in claim 13, wherein the packeting subsystem provides for the packetization of the plurality of the digital samples from the plurality of the streams of digital samples into a single data packet;

and

wherein the packetization starts and ends synchronous to the common time reference signals.

15. The gateway control system as in claim 14, wherein each of the respective data packets further comprises a payload with plurality of predefined positions;

and

wherein there is one respective predefined position in said payload for each of the streams for the digital samples from each of the streams in the respective data packet.

16. The gateway control system as in claim 15, wherein each one of the predefined positions has an associated predefined maximum length.

17. The gateway control system as in claim 15, wherein a position delimiter is provided between each of the predefined positions.

18. The gateway control system as in claim 15, wherein each one of the predefined positions has an associated respective predefined position number, wherein the controller uniquely associates the position number with a respective one of the plurality of streams of digital samples.

19. The gateway control system as in claim 15, wherein each of the predefined positions has an identifier uniquely associated with a respective one of the plurality of streams of digital samples.

20. The gateway control system as in claim 1, wherein a time reference of defined positions within defined time frames is determined responsive to the common time reference signals;

wherein the packeting subsystem provides means wherein each of the data packets is assigned an associated one of the defined positions within a one of the defined time frames, responsive to the common time reference signals.

21. The gateway control system as in claim 20 wherein the defined positions are time slots each having a common defined time interval.

22. The gateway control system as in claim 20, wherein the packetized data packets are further comprised of a header.

23. The gateway control system as in claim 20, wherein the packetized data packets are without a header.

24. The gateway control system as in claim 1, further comprising an analog to digital converter for generating the stream of digital samples.

25. The gateway control system as in claim 1, wherein each of the time frames is comprised of a plurality of predefined positions;

wherein there are a plurality of steams of digital samples;

wherein the packeting subsystem provides for the packetization of a plurality of the digital samples from each one of a respective pluaity of the streams of digital samples; and

wherein the respective digital samples from each one of the respective streams has one respective predefined position in said time frame.

26. The gateway control system as in claim 25, wherein each of the predefined positions within each of the time frames has a predefined maximum length.

27. The gateway control system as in claim 25, wherein there is a position delimiter between each of the predefined positions within each of the time frames.

28. The gateway control system as in claim 25, wherein each of the predefined positions within each of the time frames has a predefined position number, wherein the controller uniquely associates the position number with a respective one of the plurality of streams of digital samples.

29. The gateway control system as in claim 25, wherein each of the predefined positions within each of the time frames has an identifier, wherein the controller uniquely associates the identifier with a respective one of the plurality of streams of digital samples.

30. The gateway control system as in claim 1, wherein the packetization further provides for compression of the digital samples in the data packets.

31. The gateway control system as in claim 1, further comprising:

tranmit data packet selection means for selecting selected ones of the data packets as transmit data packets for transmission;

storage apparatus for storing copies of the digital samples for each of the selected ones of the transmit data packets responsive to the transmit data packet selection means.

32. The gateway control system as in claim 31, further comprising:

data packet transmission means for transmitting the transmit data packets to a far-end gateway system;

data packet receiving means for receiving transmitted data packets from the far-end gateway system;

received data packet selection means for selecting selected ones of the transmitted digital samples in data packets from the far-end gateway system as received digital samples in data packets;

association means for associating each of the selected received digital samples in data packets to respective stored copies conesponding thereto responsive to the transmit data packet selection means and the received data packet selection means; and

echo cancellation means for comparing the associated received digital samples in data packets to the respective stored copies in the storage apparatus, to provide an echo cancellation signal output responsive to the data packet receiving means, the association means, and the common time reference signal.

33. The gateway control system as in claim 32, wherein the echo cancellation signal is subtracted from the received digital samples in the received data packets from the far-end gateway system.

34. The gateway control system as in claim 32, wherein prior to comparing, the received data packets are depacketized to provide the received digital samples corresponding to the respective stored copies of the digital signals in the storage apparatus that were originally respectively packetized at the far-end gateway system;

and

wherein prior to the comparing, the received digital samples are time aligned to the stored copies of the digital samples using the common time reference signal.

35. The gateway control system as in claim 32, wherein the depacketization further provides for decompression of the digital samples in the data packets;

wherein prior to comparing, the received data packets are depacketized and decompressed to provide the received digital samples corresponding to the respective stored copies of the digital signals in the storage apparatus that were originally respectively packetized at the far-end gateway system;

wherein prior to the companng, the received digital samples are time aligned to the stored copies of the digital samples using the common time reference signal.

36. A receiving and decoding system for receiving and decoding data packets, each comprising a plurality of digital samples, the system comprising:

a source of a common time reference signal;

a source of pre-scbeduled transmission during predefined time frames responsive to the common time reference signal, of a stream of data packets, wherein each of the data packets is comprised of digital samples;

wherein the pre-scheduled transmission by the source is responsive to the common time reference signal; and

a depacketizer system for receiving and depacketizing each of the data packets to provide corresponding ones of the digital samples, responsive to the common time reference signal.

37. The receiving and decoding system as in claim 36, wherein there are a plurality of the data packets which arrive at a predefined rate with predefined intervals between the data packets;

and

wherein the depackefization of each of the data packets provides digital sample information having a duration of a predefined time interval.

38. The receiving and decoding system as in claim 37, wherein the predefined time interval is constant.

39. The receiving and decoding system as in claim 38, the system further comprising a controller for defining a plurality of predefined time frames responsive to the common time reference signal;

and

wherein each of the data packets are received in a predefined time frame synchronous with the common time reference signal.

40. The receiving and decoding system as in claim 39, wherein the data packets are compressed, and wherein the depackeizing further provides for decompression of the data packets.

41. The receiving and decoding system as in claim 40, wherein the compression is voice compression.

42. A virtual pipe communications system for communicating packetieed data over a virtual pipe comprised of a plurality of switches connected by communications links in a path, wherein a first switch within the virtual pipe is connected to receive the output of a first voice over Internet Protocol (IP) gateway and wherein a final switch within the virtual pipe is connected to provide an output coupled to transmit to a second voice over IP gateway, the system comprising:

a virtual pipe comprised of a plurality of switches connected by communications links in a path, each switch having addressable input ports and output ports;

a source of a common time reference signal, coupled to each of the switches in the virtual pipe and to the first and the second voice over IP gateway;

a controller for determining a plurality of predefined time frames responsive to the common time reference signal, and for determining a schedule of selected ones of the predefined time frames for packetization of respective packetieed data during the selected ones of the predefined time firames; and

wherein the second voice over IP gateway is comprised of a depacketizing subsystem for depacketizing the packetized data to provide an output of a plurality of digital samples, responsive to the controller.

43. The virtual pipe communications system as in claim 42, wherein the second voice over IP gateway is further comprised of a digital to analog converter.

44. The virtual pipe communications system as in claim 42, wherein the depacketization subsystem completes the depacketization prior to the respective predefined time frame associated with the packetization of the respective packet data, responsive to the controller.

45. The virtual pipe communications system as in claim 42, wherein the packetized data is comprised of data from a plurality of separate original streams of digital samples;

wherein the depacketizing system provides for the depacketization of the packetized data into a plurality of separate streams of digital samples corresponding to the respective separate original streams of the digital samples.

46. The virtalm pipe communications system as in claim 42, wherein the packetized data is comprised of a plurality of sub-units, each associated with a separate one of the streams of digital samples, with each sub-unit delimited from other adjacent sub-units by a position delimiter;

wherein the depacketizing subsystem is responsive to the position delimiters for separating the respective packetized data into the respective associated plurality of separate streams of the digital samples.

47. The virtual pipe communications system as in claim 45, wherein the packetized data has a predefined structure that is comprised of a plurality of predefined sub-units of predefined size;

wherein the depacketizng subsystem provides the depacketization into the plurality of separate streams of digital data responsive to the predefined structure.

48. The virtual pipe communications system as in claim 42, wherein the packetized data is packetized voice data.

49. The virtual pipe communications system as in claim 45, wherein the separate original streams of digital samples are separate original streams of digital voice samples.