QUALITY OF SERVICE ENHANCEMENTS FOR ADAPTIVE CODING AND MODULATION

• US 20080212517A1
• Filed: 03/07/2008
• Published: 09/04/2008
• Est. Priority Date: 10/28/2005
• Status: Active Grant

• Current Assignee: ViaSat Incorporated
• Original Assignee: ViaSat Incorporated
• Inventors: Thesling, William H.
• Granted Patent: US 7,986,624 B2
• Time in Patent Office: Days
• US Class Current: 370/316
• CPC Class Codes: H04B 7/18582 Arrangements for data linking, i.e. for data framing, for error recovery, for multiple access
• CPC Class Codes: H04B 7/18586 Arrangements for data transporting, e.g. for an end to end data transport or check
• CPC Class Codes: H04L 1/0003 by switching between different modulation schemes
• CPC Class Codes: H04L 1/0083 Formatting with frames or packets; Protocol or part of protocol for error control
• CPC Class Codes: H04L 5/023 Multiplexing of multicarrier modulation signals multicarrier modulation H04L27/2601

Abstract

A process is described to build frames for transmission with a modcode adapted to the signal quality of a destination terminal. The order of transmission may be based, at least in part, on the age of a packet as defined by a timestamp. Data packets assigned to the same modcode may be grouped in the same frame, with precedence given to older timestamps. For data packets with certain quality of service designations, timestamps may be modified to expedite forwarding. The amount of modification may, for example, be based on factors related to delay and latency.

Claims

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

a sorting unit configured to;

associate a first modcode and first timestamp with a first data packet, the first data packet destined for a link within a first signal quality range associated with the first modcode;

associate the first modcode with a second data packet destined for a link within the first signal quality range, the second data packet associated with a higher quality of service designation than the first data packet; and

associate, with the second data packet, a second timestamp modified to include an earlier arrival time than the first timestamp, the timestamp modification based at least in part on the higher quality of service designation; and

a transmitter unit, communicatively coupled with the sorting unit, and configured to transmit the second data packet before the first data packet is transmitted, the earlier transmission based at least in part on the earlier timestamp.

2. The device of claim 1, wherein the sorting unit is further configured to:

determine an amount of modification for the second timestamp based at least in part on the higher quality of service designation.

3. The device of claim 1, wherein the sorting unit is further configured to:

determine an amount of modification for the second timestamp based at least in part on a latency determination for the device.

4. The device of claim 1, wherein the sorting unit is further configured to:

determine an amount of modification for the second timestamp based at least in part on a delay between an originating transmission of the second packet and receipt of the second packet at the device.

5. The device of claim 1, wherein the sorting unit is further configured to:

determine an amount of modification for the second timestamp based at least in part on a measured load for the device.

6. The device of claim 1, wherein the transmitter unit is further configured to:

transmit additional 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 exceeding a threshold age.

7. The device of claim 6, wherein the transmitter unit is further configured to:

vary the period of the timer based at least in part on a delay associated with the additional data packets.

8. The device of claim 1, wherein the sorting unit is further configured to:

place the first data packet in a first packet forwarding queue associated with the first signal quality range; and

place the second data packet in the first packet forwarding queue in front of the first data packet based on the earlier, second timestamp.

9. The device of claim 1, wherein the sorting unit is further configured to:

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

insert, in the linked list, a second element corresponding to the second data packet and associated first signal quality, the second element inserted into the linked list in front of the first data packet based on the earlier, second timestamp.

10. The device of claim 1, wherein,

the device comprises a gateway configured to transmit downstream traffic for a digital video broadcast system;

and

the first modcode is a selected one of a plurality of modcodes, each modcode of the plurality associated with a different signal quality range of a plurality of signal quality ranges.

11. The device of claim 1, wherein the sorting unit is further configured to:

designate the second data packet with the higher quality of service designation using a quality of service lookup based on type of the second data packet.

12. The device of claim 1, wherein the sorting unit is further configured to:

change the modcode associated with the second data packet from the first modcode to a second modcode to expedite transmission of the second data packet based at least in part on the higher quality of service designation.

13. The device of claim 1, wherein the higher quality of service designation comprises a class of service designation.

14. A processor for implementing adaptive coding and modulation in a broadcast signal, the processor configured to:

associate a first timestamp with a first data packet destined for a link within a first signal quality range associated with a first modcode;

associate a second timestamp with a second data packet received after the first data packet and destined for a link within the first signal quality range, the second timestamp modified to include an earlier arrival time than the first timestamp based at least in part on a higher quality of service designation for the second data packet; and

encapsulate the second data packet in a first frame before the first data packet is encapsulated, the earlier encapsulation based at least in part on the earlier timestamp.

15. A method of implementing adaptive coding and modulation in a broadcast signal, the method comprising:

receiving a first data packet destined for a link within a first signal quality range of a plurality of signal quality ranges;

associating a first timestamp with the first data packet;

receiving, after the reception of the first data packet, a second data packet destined for a link within the first signal quality range, the second data packet associated with a higher quality of service designation than the first data packet;

associating, with the second data packet, a second timestamp modified to include an earlier arrival time than the first timestamp, the timestamp modification based at least in part on the higher quality of service designation; and

encapsulating the second data packet in a first frame before the first data packet is encapsulated, the earlier encapsulation based at least in part on the earlier timestamp.

16. The method of claim 15, further comprising:

transmitting the second data packet before the first data packet is transmitted, the earlier transmission based at least in part on the earlier arrival time for the second timestamp.

17. The method of claim 16, further comprising:

determining an amount of modification for the second timestamp based at least in part on an estimated delay between the receipt and transmission of the second packet.

18. The method of claim 15, further comprising:

determining an amount of modification for the second timestamp based at least in part on attributes of the higher quality of service designation.

19. The method of claim 15, further comprising:

determining an amount of modification for the second timestamp based at least in part on an age attributed to the second data packet.

20. The method of claim 15, further comprising:

determining an amount of modification for the second timestamp based at least in part on relative quality of service designations for other received data packets buffered waiting to be transmitted.

21. The method of claim 15, further comprising:

transmitting additional data packets according to a defined order of progression; and

interrupting the defined order of progression upon expiration of a timer to transmit the second data packet based on a determination that the second timestamp exceeds a threshold age.

22. The method of claim 21, further comprising:

varying the period of the timer based at least in part on a delay associated with the additional data packets.

23. The method of claim 15, further comprising:

placing the first data packet in a first packet forwarding queue associated with the first signal quality range; and

placing the second data packet in the first packet forwarding queue in front of the first data packet based on the earlier, second timestamp.

24. The method of claim 15, further comprising:

changing the modcode associated with the second data packet from the first modcode to a second modcode to expedite transmission of the second data packet based at least in part on the higher quality of service designation.

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

a gateway configured to;

associate a first timestamp with a data packet destined for a link within a first signal quality range associated with a first modcode;

associate a second timestamp with a second data packet received after the first data packet and destined for a link within the first signal quality range, the second timestamp modified to include an earlier arrival time than the first timestamp based at least in part on a higher quality of service designation for the second data packet; and

transmit the second data packet in a wireless signal to the satellite before the first data packet is transmitted, the earlier transmission based at least in part on the earlier timestamp;

the satellite, communicatively coupled with a subscriber terminal and the gateway, and configured to receive the wireless signal from the gateway and retransmit the received signal to the subscriber terminal; and

the subscriber terminal configured to receive the signal transmitted via the satellite.