Low-latency automatic repeat request packet recovery mechanism for media streams

• US 20060104279A1
• Filed: 11/18/2005
• Published: 05/18/2006
• Est. Priority Date: 11/18/2004
• Status: Active Grant

• Current Assignee: Qvidium Technologies, Inc.
• Original Assignee: Qvidium Technologies, Inc.
• Inventors: Beer, John C., Fellman, Ronald D.
• Granted Patent: US 7,522,528 B2
• Time in Patent Office: Days
• US Class Current: 370/392
• CPC Class Codes: H04L 12/2854 Wide area networks, e.g. public data networks

Abstract

An Automatic Repeat reQuest (ARQ) error correction method optimized for protecting real-time audio-video streams for transmission over packet-switched networks. Embodiments of this invention provide bandwidth-efficient and low-latency ARQ for both variable and constant bit-rate audio and video streams. Embodiments of this invention use timing constraints to limit ARQ latency and thereby facilitate the use of ARQ packet recovery for the transport of both constant bit rate and variable bit rate media streams.

Claims

1. A low-latency automatic repeat request packet recovery mechanism for media streams comprising:

a packet store module configured to store at least one packet from a packet stream;

a retransmit module configured to fetch said at least one requested packet from said packet store module;

a timestamp unit configured to timestamp a local clock time in a transmission packet in said modified packet stream;

said packet store module and said retransmit module comprising an automatic repeat request module;

said automatic repeat request module and said timestamp unit comprising a transmitter packet processing module;

a receiver timestamp unit configured to timestamp an incoming packet using a receiver local clock;

a reorder/jitter packet buffer module configured to hold said incoming packet for an amount of time to allow for out-of-order packets to arrive in time for proper sequence insertion;

a gate configured to add a fixed delay to a packet timestamp and compare said time stamp with said receiver local clock to control a release time for a received packet;

a receiver automatic repeat request packet recovery module configured to receive said received packet detect gaps in sequence number, and request lost packets from said transmitter packet processing module by sending a retransmission request;

a recovered stream hold-off gate configured to delay, by a fixed time synchronized to a recovered transmit clock, an output of any packets from said receiver to allow output of a jitter-free and error free ordered and continuous stream of packets;

said receiver timestamp unit, said reorder/jitter packet buffer module, said gate and said receiver automatic repeat request packet recovery module comprising a receiver module; and

,

said transmitter packet processing module configured to transmit said modified packet stream to said receiver module.

2. The system of claim 1 further comprising a packet merge unit which comprises a statistical multiplexer configured to buffer multiple streams of packets into a single stream to limit packet burst.

3. The system of claim 1 further comprising a retransmission packet-storm suppression module configured to temporarily suspend retransmission when a transmission level exceeds a threshold wherein said retransmission packet-storm suppression module is also configured to send at least one requested packet wherein said threshold comprises a fixed percentage of a network link capacity.

4. The system of claim 1 wherein said local clock is synchronized with a receiver local clock.

5. The system of claim 1 wherein receiver module comprises a clock recovery module configured to recover a clock value.

6. The system of claim 1 wherein transmitter packet processing module comprises an IP packetizer.

7. The system of claim 1 wherein receiver module comprises an IP de-packetizer.

8. A method for utilizing a low-latency automatic repeat request packet recovery mechanism for media streams comprising:

storing at least one packet from a packet stream in a packet store module;

fetching at least one requested packet via a retransmit module from said packet store module;

outputting a modified packet stream;

timestamping a local clock time in a transmission packet in said modified packet stream via a timestamp unit;

coupling said packet store module and said retransmit module to form an automatic repeat request module;

coupling said automatic repeat request module and said timestamp unit to form a transmitter packet processing module;

timestamping an incoming packet via a receiver timestamp unit using a receiver local clock;

holding said incoming packet in a reorder/jitter packet buffer module for an amount of time to allow for out-of-order packets to arrive in time for proper sequence insertion;

adding a fixed delay to a packet timestamp via a gate and comparing said time stamp with said receiver local clock to control a release time for a received packet;

receiving said received packet from said transmitter packet processing module via a receiver automatic repeat request packet recovery module, detecting gaps in sequence number, and requesting lost packets from said transmitter packet processing module by sending a retransmission request;

delaying via a recovered stream hold-off gate a fixed time synchronized to a recovered transmit clock, an outptitting, of any packets from said receiver to allow output of a jitter-free and error free ordered and continuous stream of packets;

coupling said receiver timestamp unit, said reorder/jitter packet buffer module, said gate and said receiver automatic repeat request packet recovery module to form a receiver module; and

,

transmitting said modified packet stream to said receiver module from said transmitter packet processing module.

9. The method of claim 8 further comprising:

suspending retransmission via a retransmission packet-storm suppression module when a transmission level exceeds a threshold;

sending said at least one requested packet to said retransmission packet-storm suppression module; and

,

accepting said packet stream and said retransmission packet stream via a packet merge module.

10. The method of claim 8 further comprising coupling a packet merge unit to a statistical multiplexer configured to buffer multiple streams of packets into a single stream to limit packet burst.

11. The method of claim 9 further comprising setting said threshold to a fixed percentage of a network link capacity.

12. The method of claim 8 further comprising synchronizing said local clock with a receiver local clock.

13. The method of claim 8 recovering a clock value in said receiver module via a clock recovery module.

14. The method of claim 8 further comprising coupling said transmitter packet processing module comprises with an IP packetizer.

15. The method of claim 8 further comprising coupling said receiver module with an IP de-packetizer.

16. A system for utilizing a low-latency automatic repeat request packet recovery mechanism for media streams comprising:

means for storing at least one packet from a packet stream in a packet store module;

means for fetching at least one requested packet via a retransmit module from said packet store module;

means for outputting a modified packet stream;

means for timestamping a local clock time in a transmission packet in said modified packet stream via a timestamp unit;

means for coupling said packet store module and said retransmit module to form an automatic repeat request module;

means for coupling said automatic repeat request module and said timestamp unit to form a transmitter packet processing module;

means for timestamping an incoming packet via a receiver timestamp unit using a receiver local clock;

means for holding said incoming packet in a reorder/jitter packet buffer module for an amount of time to allow for out-of-order packets to arrive in time for proper sequence insertion;

means for adding a fixed delay to a packet timestamp via a gate and comparing said time stamp with said receiver local clock to control a release time for a received packet;

means for receiving said received packet from said transmitter packet processing module via a receiver automatic repeat request packet recovery module, means for detecting gaps in sequence number, and means for requesting lost packets from said transmitter packet processing module by sending a retransmission request;

means for delaying via a recovered stream hold-off gate a fixed time synchronized to a recovered transmit clock, and means for outputting of any packets from said receiver to allow output of a jitter-free and error free ordered and continuous stream of packets;

means for coupling said receiver timestamp unit, said reorder/jitter packet buffer module, said gate and said receiver automatic repeat request packet recovery module to form a receiver module; and

,

means for transmitting said modified packet stream to said receiver module from said transmitter packet processing module.

17. The system of claim 16 further comprising:

means for suspending retransmission via a retransmission packet-storm suppression module when a transmission level exceeds a threshold;

means for sending said at least one requested packet to said retransmission packet-storm suppression module; and

,

means for accepting said packet stream and said retransmission packet stream via a packet merge module.

18. The system of claim 16 further comprising means for coupling a packet merge unit to a statistical multiplexer configured to buffer multiple streams of packets into a single stream to limit packet burst.

19. The system of claim 17 further comprising means for setting said threshold to a fixed percentage of a network link capacity.

20. The system of claim 16 further comprising means for synchronizing said local clock with a receiver local clock.