ADAPTIVE CODING AND MODULATION FLOW CONTROL AND TRAFFIC SHAPING SYSTEMS AND METHODS

• US 20070097852A1
• Filed: 10/30/2006
• Published: 05/03/2007
• Est. Priority Date: 10/28/2005
• Status: Active Grant

• Current Assignee: ViaSat Incorporated
• Original Assignee: ViaSat Incorporated
• Inventors: Thesling, William
• Granted Patent: US 7,689,162 B2
• Time in Patent Office: Days
• US Class Current: 370/206
• 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 for a plurality of packets destined for different link conditions, the method comprising:

assigning a different modcode to each of at least a subset of a plurality of signal quality ranges; and

dynamically varying one or more of the plurality of signal quality ranges to modify a reliability margin for delivery of data packets destined for a link with a signal quality within the varied one or more ranges.

2. The method of claim 1, wherein varying one or more of the plurality of signal quality ranges comprises:

increasing a minimum signal quality for the one or more of the plurality of signal quality ranges when a latency measurement related to flow of the plurality of packets decreases, to thereby increase the reliability margin.

3. The method of claim 2, wherein varying one or more of the plurality of signal quality ranges comprises:

decreasing a minimum signal quality for the one or more of the plurality of signal quality ranges when a latency measurement related to flow of the plurality of packets increases, to thereby decrease the reliability margin.

4. The method of claim 1, wherein varying one or more of the plurality of signal quality ranges comprises:

varying, in response to change in a measurement of traffic load, a minimum signal quality associated with the one or more of the plurality of signal quality ranges, thereby modifying the reliability margin.

5. The method of claim 1, further comprising:

measuring a delay between a timestamp and transmission of one or more transmitted data packets to produce a latency measurement.

6. The method of claim 1, further comprising:

transmitting a subset of the plurality of data 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 data packets, the out of order packet exceeding a threshold age.

7. The method of claim 6, further comprising:

varying the period of 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 data packets when a latency measurement exceeds a threshold.

9. The method of claim 1, further comprising:

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

10. The method of claim 1, further comprising:

fragmenting, when a latency measurement is above a threshold, an internet protocol data packet of the plurality of data 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 one or more of the plurality of signal quality ranges; and

iterating through a linked list to identify elements associated with links within a second of the one or more 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 one or more 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 for a plurality of packets destined for different link conditions, the device comprising:

a processing unit configured to;

assign a different modcode to each of at least a subset of a plurality of signal quality ranges; and

dynamically vary one or more of the plurality of signal quality ranges to modify a reliability margin for delivery of data packets destined for a link within the varied signal range; and

a transmitting unit configured to;

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

17. The device of claim 16, wherein,

the processing unit is configured to:

increase a minimum signal quality for the one or more of the plurality of signal quality ranges when a latency measurement decreases, to thereby increase the reliability margin for a least a subset of the plurality of packets destined for a link within the increased range.

18. The device of claim 16, wherein,

the processing unit is configured to:

decrease a minimum signal quality associated with the one or more of the plurality of signal quality ranges when a latency measurement increases, to thereby decrease the reliability margin for a least a subset of the plurality of packets destined for a link within the decreased range.

19. The device of claim 16, wherein,

the processing unit is configured to:

vary, in response to a change in a measurement of traffic load, a minimum signal quality associated with the one or more of the plurality of signal quality ranges, thereby modifying the reliability margin for at least a subset of the plurality of packets destined for a link within the varied range.

20. The device of claim 16, wherein,

the processing unit is configured to:

measure a delay between a timestamp and transmission of one or more transmitted data packets to produce a latency measurement.

21. The device of claim 16, wherein,

the transmitting unit is configured to:

transmit a subset of the plurality of data 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 data packets, the out of order packet exceeding a threshold age and not included in the subset.

22. The device of claim 21, wherein,

the transmitting unit is configured to:

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

23. The device of claim 16, wherein,

the processing unit is configured to:

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

24. The device of claim 16, wherein,

the processing unit is configured to:

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

25. A device for implementing adaptive modulation and coding for packets destined for different link conditions, the device comprising:

means for assigning a different modcode to each of at least a subset of a plurality of signal quality ranges;

means for dynamically varying one or more of the plurality of signal quality ranges to modify a reliability margin for delivery of data packets destined for a link within the varied signal range; and

means for transmitting at least a subset of the plurality of packets destined for a link within the varied signal range according to the assigned modcode.