Adaptive coding and modulation for broadband data transmission

• US 7,680,040 B2
• Filed: 10/30/2006
• Issued: 03/16/2010
• Est. Priority Date: 10/28/2005
• Status: Active Grant

• Current Assignee: ViaSat Incorporated
• Original Assignee: ViaSat Incorporated
• Inventors: Thesling, William H.
• Primary Examiner(s): Chou; Albert T
• Application Number:
  US11/554,206
• Publication Number:
  US 20070116151A1
• Time in Patent Office: 1,233 Days
• Field of Search: 370/206, 370/230, 370/329, 370/468, 455/464, 714/755
• US Class Current: 370/230
• 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 coding and modulation in a satellite communications network, the method comprising:

associating a first modcode of a first order with a first signal quality range;

associating a second modcode of a second order higher than the first order with a second signal quality range of better quality than the first signal quality range;

receiving a first packet destined for a first link within the first signal quality range and a second packet destined for a second link within the second signal quality range;

encapsulating the first packet in a payload portion of a first frame;

determining that an available portion of the payload portion is insufficient to fit the second packet;

fragmenting the second packet into a first fragment sized to fill the available portion and a second fragment;

encapsulating the first fragment in the available portion of the payload of the first frame; and

transmitting the payload portion of the first frame in the satellite communications network according to the first modcode.

2. The method of claim 1, further comprising:

varying at least one of the first signal quality range and the second signal quality range to modify a reliability margin for packets destined for a link within the varied signal quality range.

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

varying at least one of the first signal quality range and the second signal quality range responsive to latency associated with the transmitting step.

4. The method of claim 1, further comprising:

transmitting the second fragment in a second frame according to the second modcode.

5. The method of claim 1, wherein the encapsulating the first fragment step further comprises:

applying a policy of encapsulating packets associated with different modcodes in one frame to be transmitted according to a lowest order modcode of the different modcodes, the policy applied when there are no remaining packets associated with the lowest order modcode.

6. The method of claim 5, wherein the applying step comprises:

determining a length of a prospective pad for the first frame;

determining that no packet associated with the first modcode remains to fill the prospective pad; and

filling the prospective pad with the first fragment.

7. The method of claim 1, further comprising:

transmitting additional frames in the broadcast signal according to a defined order of progression; and

interrupting the defined order of progression upon expiration of a timer to transmit a packet exceeding a threshold age.

8. The method of claim 7, further comprising:

varying a period of the timer responsive to a delay associated with transmitting the additional frames.

9. The method of claim 1, wherein,

the associating the first modcode with the first packet comprises placing the first packet in a first packet forwarding queue associated with the first signal quality range;

and

the associating the second modcode with the second packet comprises placing the second packet in a second packet forwarding queue associated with the second signal quality range.

10. The method of claim 1, further comprising:

inserting, in a linked list, a first element corresponding to the first packet and associated first signal quality;

inserting, in the linked list, a second element corresponding to the second packet and associated second signal quality; and

iterating through the linked list to identify a set of packets for encapsulation and transmission responsive to a signal quality associated with each element of the linked list.

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

12. The method of claim 1, wherein the first and second signal quality ranges are ranges of signal quality comprising at least one of a signal to noise ratio, an estimated signal to noise ratio, a bit error rate, or a receive power level.

13. A device for implementing adaptive modeodes in a satellite communications network, the device comprising:

a sorter configured to;

associate a first modcode of a first order with a first packet to be received on a first link defined by a signal quality in a first signal quality range;

associate a second modcode of a second order, higher than the first order, with a second packet to be received on a second link defined by a signal quality in a second signal quality range of better quality than the first signal quality range;

an encapsulator, communicatively coupled with the sorter, and configured to;

encapsulate the first packet in a payload portion of a first frame;

determine that an available portion of the payload portion is insufficient to fit the second packet;

fragment the second packet into a first fragment sized to fill the available portion and a second fragment; and

encapsulate the first fragment in the available portion of the payload of the first frame; and

a modulation and coding module, communicatively coupled with the encapsulator, and configured to encode and map a payload of the frame according to the first modcode.

14. The device of claim 13, wherein,

the sorter is further configured to vary at least one of the first signal quality range and the second signal quality range to modify a reliability margin for a transmitted packet destined for a link within the varied signal quality range.

15. The device of claim 13, wherein,

the sorter is further configured to vary at least one of the first signal quality range and the second signal quality range responsive to latency associated with the transmitting step.

16. The device of claim 13, wherein,

the encapsulator is further configured to:

encapsulate the second fragment in a second frame to be transmitted according to the second modcode.

17. The device of claim 13, wherein,

the sorter is configured to group packets associated with different modcodes for encapsulation in one frame to be transmitted according to a lowest order modcode of the different modcodes, the grouping to occur when there are no remaining packets associated with the lowest order modcode.

18. The device of claim 13, further comprising a transmitter configured to:

transmit additional frames in the broadcast signal according to a defined order of progression; and

interrupt the defined order of progression upon expiration of a timer to transmit a packet exceeding a threshold age.

19. The device of claim 18, wherein,

the transmitter is further configured to vary a period of timer responsive to a latency associated with transmitting the additional frames.

20. A device for implementing adaptive coding and modulation in a satellite communications network, the device comprising:

means for associating a first modcode of a first order with a first signal quality range;

means for associating a second modcode of a second order with a second signal quality range, the second order being higher than the first order and the second signal quality range being of a better quality than the first signal quality range;

means for receiving a plurality of first packets destined for a first link within the first signal quality range;

means for receiving a plurality of second packets destined for a second link within the second signal quality range;

means for encapsulating the first packet in a payload portion of a first frame;

means for determining that an available portion of the payload portion is insufficient to fit the second packet;

means for fragmenting the second packet into a first fragment sized to fill the available portion and a second fragment;

means for encapsulating the first fragment in the available portion of the payload of the first frame; and

means for transmitting the payload of the first frame through the satellite communications network according to the first modcode.

21. A device for implementing adaptive coding and modulation in a satellite communications network, the device comprising:

a sorter configured to;

associate a first modcode of a first order with a first packet to be transmitted on a first link defined by a signal quality in a first signal quality range;

associate a second modcode of a second order with a second packet to be transmitted on a second link defined by a signal quality in a second signal quality range, the second order being higher than the first order and the second signal quality range being of a better quality than the first signal quality range;

receive a plurality of first packets destined for one or more links within the first signal quality range; and

receive a second packet destined for a second link within the second signal quality range;

an encapsulator, communicatively coupled with the sorter, configured to;

encapsulate the plurality of first packets in a payload portion of the first frame;

determine that no packet associated with the first modcode remains to fill the frame;

fragment the second packet into a first fragment sized to fill the available portion and a second fragment; and

encapsulate the first fragment in the available portion of the payload of the first frame; and

a modulation and coding module, communicatively coupled with the sorter, configured to encode and map the first frame according to the first modcode for transmission in the satellite communications network.