ADAPTIVE CODING AND MODULATION QUEUING METHODS AND DEVICES

• US 20070116152A1
• Filed: 10/30/2006
• Published: 05/24/2007
• Est. Priority Date: 10/28/2005
• Status: Active Grant

• Current Assignee: ViaSat Incorporated
• Original Assignee: ViaSat Incorporated
• Inventors: Thesling, William
• Granted Patent: US 7,684,425 B2
• Time in Patent Office: Days
• US Class Current: 375/326
• 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 using a plurality of packet forwarding queues, the method comprising:

assigning a different modcode to each of the plurality of packet forwarding queues, each queue associated with a select one of a plurality of signal quality ranges;

placing each respective packet of a plurality of data packets into a selected one of the packet forwarding queues, each selected queue associated with a signal quality range encompassing a signal quality of a link to which the respective packet is destined;

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 and not included in the subset.

2. The method of claim 1, further comprising:

varying the period of timer based at least in part on a latency associated with transmitting from the packet forwarding queues.

3. The method of claim 1, wherein the threshold age comprises the age of the second oldest data packet remaining in the packet forwarding queues.

4. The method of claim 1, wherein the transmitting according to the defined order of progression comprises:

transmitting each data packet in a first selected packet forwarding queue associated with a first modcode; and

incrementing to a second selected packet forwarding queue with a next higher order second modcode to transmit a packet from the second selected queue.

5. The method of claim 4, wherein the transmitting according to the defined order of progression further comprises:

transmitting at least one data packet from the first selected queue and the data packet from the second selected queue in a single frame according the first modcode.

6. The method of claim 5, wherein the transmitting according to the defined order of progression further comprises:

determining a length of a prospective pad for the at least one data packet from the first selected queue;

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

filling the prospective pad with the data packet associated with the second modcode.

7. The method of claim 1, further comprising:

utilizing a counter to associate an order with the plurality of data packets before entering the queues; and

holding transmission of a packet in the packet forwarding queues when the packet is out of the order specified by the counter.

8. The method of claim 1, further comprising:

blocking additional data packets from entering the packet forwarding queues when the out of order packet exceeds a second threshold age.

9. The method of claim 8, further comprising:

allowing data packets associated with a threshold quality or class of service to enter the packet forwarding queues.

10. The method of claim 1, further comprising:

varying at least one of the plurality of signal quality ranges to increase a reliability margin when a delay associated with transmitting from the packet forwarding queues decreases.

11. The method of claim 1, further comprising:

varying at least one of the plurality of signal quality ranges to decrease a reliability margin when a delay associated with transmitting from the packet forwarding queues increases.

12. The method of claim 1, wherein the transmitting according to the defined order of progression comprises:

fragmenting an internet protocol data packet of the plurality of data packets into first fragment and second fragment, each fragment associated with a first selected queue associated with 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.

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

14. 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.

15. A device implementing adaptive coding and modulation by assigning different modcodes for links of different signal qualities, the method comprising:

a plurality of packet forwarding queues, each queue associated with a different modcode and a select one of a plurality of signal quality ranges;

a queueing unit coupled with the plurality of queues, and configured to place each respective packet of a plurality of data packets into a select one of the packet forwarding queues, the selected queue associated with a signal quality range encompassing a signal quality of a link to which the respective packet is destined; and

a transmitting unit, coupled with the plurality of queues, and 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 a packet of the plurality of data packets, the packet exceeding a threshold age and not included in the subset.

16. The device of claim 15, wherein,

the transmitting unit is further configured to vary the period of timer based at least in part on latency associated with transmitting from the packet forwarding queues.

17. The device of claim 15, wherein the threshold age comprises an age of the second oldest data packet remaining in the packet forwarding queues.

18. The device of claim 15, wherein the defined order of progression comprises the transmitting unit configured to:

transmit each data packet in a first selected packet forwarding queue associated with a first modcode; and

increment to a second selected packet forwarding queue with a next higher order second modcode to transmit a packet from the second selected queue.

19. The device of claim 18, wherein the defined order of progression further comprises the transmitting unit configured to:

transmit at least one data packet from the first selected queue and the data packet from the second selected queue in a single frame according the first modcode.

20. The device of claim 15, wherein,

the queueing unit is further configured to utilize a counter to associate an order with each of the plurality of data packets before entering the packet forwarding queues;

and

the transmitting unit is further configured to hold transmission of a packet in the packet forwarding queues when the packet is out of the order specified by the counter.

21. The device of claim 15, wherein,

the queueing unit is further configured to block additional data packets from entering the packet forwarding queues when the out of order packet exceeds a second threshold age.

22. The device of claim 15, wherein,

the queueing unit is further configured to allow data packets associated with a threshold quality of service to enter the packet forwarding queues.

23. The device of claim 15, wherein,

the queueing unit is further configured to vary at least one of the plurality of signal quality ranges to modify a reliability margin for data packets destined for a link within the varied signal quality range.

24. The device of claim 15, wherein the transmitting unit is further configured to:

fragment an internet protocol data packet of the plurality of data packets into first fragment and second fragment, each fragment associated with a first selected queue associated with 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.

25. The device of claim 15, wherein the device implements adaptive coding and modulation in accordance with a DVB-S2 standard.

26. The device of claim 15, 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.

27. A device for implementing adaptive coding and modulation by assigning different modcodes for links of different signal qualities, the device comprising:

means for assigning a different modcode to each of a plurality of packet forwarding queues, each queue associated with a select one of a plurality of signal quality ranges;

means for placing each respective packet of a plurality of data packets into a selected one of the packet forwarding queues, each selected queue associated with a signal quality range encompassing a signal quality of a link to which the respective packet is destined;

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

means for 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 and not included in the subset.