Adaptive coding and modulation flow control and traffic shaping systems and methods

• US 7,689,162 B2
• Filed: 10/30/2006
• Issued: 03/30/2010
• Est. Priority Date: 10/28/2005
• Status: Active Grant

• Current Assignee: ViaSat Incorporated
• Original Assignee: ViaSat Incorporated
• Inventors: Thesling, William H.
• Primary Examiner(s): Bost; Dwayne
• Assistant Examiner(s): THAO, CHHEAN K
• Application Number:
  US11/554,263
• Publication Number:
  US 20070097852A1
• Time in Patent Office: 1,247 Days
• Field of Search: 370/329, 370/349, 370/394, 370/415, 455/3.02, 455/427
• US Class Current: 455/3.02
• CPC Class Codes: H04B 7/18543 for adaptation of transmission parameters, e.g. power control for detecting or preventing errors in the information received H04L1/00
• CPC Class Codes: H04B 7/18582 Arrangements for data linking, i.e. for data framing, for error recovery, for multiple access
• CPC Class Codes: H04L 1/0003 by switching between different modulation schemes
• CPC Class Codes: H04L 1/0007 by modifying the frame length
• CPC Class Codes: H04L 1/0009 by adapting the channel coding H04L1/1812 takes precedence
• CPC Class Codes: H04L 1/0016 involving special memory structures, e.g. look-up tables
• CPC Class Codes: H04L 1/0021 in which the algorithm uses adaptive thresholds
• CPC Class Codes: H04L 1/0026 Transmission of channel quality indication
• CPC Class Codes: H04L 1/0083 Formatting with frames or packets; Protocol or part of protocol for error control
• CPC Class Codes: H04L 2001/0093 Point-to-multipoint
• CPC Class Codes: H04L 27/0008 arrangements for allowing a transmitter or receiver to use more than one type of modulation negotiating modulation type for two-way transmission paths H04L5/1453
• CPC Class Codes: H04L 47/6215 Individual queue per QOS, rate or priority
• CPC Class Codes: H04L 5/023 Multiplexing of multicarrier modulation signals multicarrier modulation H04L27/2601
• CPC Class Codes: H04W 28/10 Flow control between communication endpoints
• CPC Class Codes: H04W 72/1221 based on age of data to be sent
• CPC Class Codes: H04W 72/542 using measured or perceived quality
• CPC Class Codes: H04W 80/00 Wireless network protocols or protocol adaptations to wireless operation
• CPC Class Codes: H04W 84/06 Airborne or Satellite Networks space-based or airborne stations H04B7/185

Abstract

A process is described to build physical layer frames with a modcode adapted to the signal quality of a destination terminal. Data packets assigned to the same modcode may be sent in the same frame, although packets associated with higher modcodes may be used to complete a frame before switching to the applicable higher modcode for construction of subsequent frames. After an interval, the order of progression is restarted with an out of order packet above a threshold age. Flow control filtering mechanisms and a variable reliability margin may be used to adapt dynamically to the current data traffic conditions.

Claims

1. A method of implementing adaptive modulation and coding at a gateway for a plurality of packets in a satellite communications network, the method comprising:

assigning a different modcode to each of a plurality of signal quality ranges, wherein a first range of the plurality of signal quality ranges is associated with a first modcode, a second range of the plurality of signal quality ranges is associated with a second modcode, and a boundary between the first range and the second range defines a transition between the first modcode and the second modcode;

monitoring a packet traffic load at the gateway; and

dynamically adjusting, responsive to when the monitored traffic load at the gateway crosses a threshold measurement, the boundary to modify a reliability margin for delivery of packets destined for a link with a signal quality within the first or second range.

2. The method of claim 1, wherein the adjusting comprises:

increasing a minimum signal quality boundary for the second range when a latency measurement at the gateway related to flow of the plurality of packets decreases, to thereby increase the reliability margin, wherein the packet traffic load at the gateway comprises the latency measurement.

3. The method of claim 2, wherein the adjusting comprises:

decreasing a minimum signal quality boundary for the second range when a latency measurement at the gateway related to flow of the plurality of packets increases, to thereby decrease the reliability margin, wherein the packet traffic load at the gateway comprises the latency measurement.

4. The method of claim 1, wherein the adjusting comprises:

decreasing, in response to an increase in a measurement of packet traffic load, a minimum signal quality boundary associated with the second range, thereby modifying the reliability margin.

5. The method of claim 1, further comprising:

measuring a delay at the gateway between a timestamp and transmission of one or more transmitted packets to produce a latency measurement comprising the packet traffic load at the gateway.

6. The method of claim 1, further comprising:

transmitting a subset of the plurality of packets according to a defined order of progression; and

interrupting the defined order of progression upon expiration of a timer to transmit an out of order packet of the plurality of packets, the out of order packet exceeding a threshold age.

7. The method of claim 6, further comprising:

varying the period of the timer based at least in part on a latency measurement related to flow of the plurality of packets.

8. The method of claim 1, further comprising:

blocking additional packets when a latency measurement exceeds the threshold measurement.

9. The method of claim 1, further comprising:

allowing packets associated with a threshold quality of service or class of service while blocking other packets when a latency measurement exceeds the threshold measurement.

10. The method of claim 1, further comprising:

fragmenting, when a latency measurement is above the threshold measurement, an internet protocol packet of the plurality of packets into first fragment and second fragment, each fragment associated with a signal quality range associated with the varied signal range assigned to a first modcode;

transmitting the first fragment according to a second modcode; and

transmitting the second fragment according to the first modcode, the first modcode of higher order than the second modcode.

11. The method of claim 1, wherein the reliability margin is zero.

12. The method of claim 1, wherein the adaptive coding and modulation is implemented in accordance with a DVB-S2 standard.

13. The method of claim 1, wherein the signal quality comprises at least one of a signal to noise ratio, an estimated signal to noise ratio, a bit error rate, a receive power level, and another communication link quality indicator.

14. The method of claim 1, further comprising:

iterating through a linked list to identify elements associated with links within a first of the plurality of signal quality ranges; and

iterating through a linked list to identify elements associated with links within a second of the plurality of signal quality ranges.

15. The method of claim 1, further comprising:

associating a different packet forwarding queue with each of the plurality of signal quality ranges; and

placing each of the plurality of packets into a packet forwarding queue associated with a signal quality range including the signal quality of a link to which the each packet is destined.

16. A device for implementing adaptive modulation and coding at a gateway for a plurality of packets, the device comprising:

a processor configured to;

assign a different modcode to each of a plurality of signal quality ranges, wherein a first range of the plurality of signal quality ranges is associated with a first modcode, a second range of the plurality of signal quality ranges is associated with a second modcode, and a boundary between the first range and the second range defines a transition between the first modcode and the second modcode;

monitor a packet traffic load at the gateway; and

dynamically adjust, responsive to when the monitored traffic load at the device crosses a threshold measurement, the boundary to modify a reliability margin for delivery of packets destined for a link within the selected first or second range; and

a transmitter, communicatively coupled with the processor and configured to;

transmit a subset of the plurality of packets destined for a link within the selected range according to the assigned modcode.

17. The device of claim 16, wherein, the processor is configured to:

increase a minimum signal quality boundary for the second range when a latency measurement at the gateway decreases, to thereby increase the reliability margin for one or more of the subset of the plurality of packets destined for a link within the second range, wherein the packet traffic load at the gateway comprises the latency measurement.

18. The device of claim 16, wherein, the processor is configured to:

decrease a minimum signal quality boundary associated with the second range when a latency measurement at the gateway increases, to thereby decrease the reliability margin for one or more of the subset of the plurality of packets destined for a link within the second range, wherein the packet traffic load at the gateway comprises the latency measurement.

19. The device of claim 16, wherein, the processor is configured to:

decrease, in response to an increase in a measurement of packet traffic load, a minimum signal quality boundary associated with the second range, thereby decreasing the reliability margin for one or more of the subset of the plurality of packets destined for a link within the second range.

20. The device of claim 16, wherein, the processor is configured to:

measure a delay at the gateway between a timestamp and transmission of one or more transmitted packets to produce a latency measurement comprising the packet traffic load at the gateway.

21. The device of claim 16, wherein, the transmitter is configured to:

transmit a subset of the plurality of packets according to a defined order of progression; and

interrupt the defined order of progression upon expiration of a timer to transmit an out of order packet of the plurality of packets, the out of order packet exceeding a threshold age and not included in the subset.

22. The device of claim 21, wherein, the transmitter is configured to:

vary the period of the timer based at least in part on a latency measurement related to transmitting a subset of the plurality of packets.

23. The device of claim 16, wherein, the processor is configured to:

block additional packets from being processed when a latency measurement exceeds the threshold measurement.

24. The device of claim 16, wherein, the processor is configured to:

allow packets associated with a threshold quality of service or class of service to be processed, while blocking other packets when a latency measurement exceeds a threshold.

25. A device for implementing adaptive modulation and coding for packets, the device comprising:

means for assigning a different modcode to each of a plurality of signal quality ranges, wherein a first range of the plurality of signal plurality ranges is associated with a first modcode, a second range of the plurality of signal quality ranges is associated with a second modcode and a boundary between the first range and the second range defines a transition between the first modcode and the second modcode;

means for monitoring a packet traffic load at the device;

means for dynamically adjusting, responsive to when the monitored traffic load at the gateway crosses a threshold measurement, the boundary to modify a reliability margin for delivery of packets destined for a link within the first or second range; and

means for transmitting a subset of the plurality of packets destined for a link within the selected range according to the assigned modcode.