Adaptive coding and modulation for broadband data transmission
View Patent ↗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.
1. A method of controlling the flow of data traffic for a broadcast signal implementing adaptive coding and modulation, the method comprising:
dynamically assigning a modcode of a plurality of modcodes to each of a plurality of data packets based at least in part on a signal quality of a link on which each respective packet is destined;
associating a timestamp with each of the plurality of data packets;
transmitting a subset of the plurality of data packets according to a defined order of progression, wherein the transmitting according to the defined order of progression comprises:
transmitting each data packet associated with a first modcode of the plurality of modcodes; and
incrementing to a next higher order second modcode of the plurality of modcodes to transmit a data packet associated with an oldest timestamp of the plurality of data packets associated with the second modcode; and
interrupting the defined order of progression upon expiration of a timer to transmit an out of order packet with a timestamp exceeding a first threshold age, wherein the out of order packet comprises one of the plurality of packets not included in the subset.
2. The method of claim 1 , wherein the first threshold age comprises the timestamp of the second oldest of the plurality of data packets not included in the subset.
3. The method of claim 1 , further comprising:
blocking additional incoming data packets when the out of order packet exceeds a second threshold age.
4. The method of claim 3 , further comprising:
allowing only data packets associated with a threshold quality or class of service to enter while blocking the additional packets.
5. The method of claim 1 , further comprising:
restarting the defined order of progression from the out of order packet.
6. The method of claim 1 , further comprising:
varying the period of timer based at least in part on a delay associated with transmitting from the packet forwarding queues.
7. The method of claim 1 , wherein the transmitting according to the defined order of progression further comprises:
transmitting at least one data packet associated with a first modcode and the data packet associated with the second modcode in a single frame according the first modcode.
8. The method of claim 1 , 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 associated with a first modcode;
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.
9. The method of claim 1 , further comprising:
utilizing a counter to associate an order with the plurality of data packets; and
holding transmission of a data packet of the plurality of data packets when the packet is out of the order specified by the counter.
10. The method of claim 1 , further comprising:
varying a signal quality range associated with one or more of the plurality of modcodes to modify a reliability margin for at least a subset of the plurality of data packets destined for a link within the varied signal quality range.
11. The method of claim 1 , wherein the dynamically assigning the modcode step comprises:
placing selected data packets of the plurality of data packet into selective ones of a plurality of packet forwarding queues each associated with different signal quality ranges.
12. The method of claim 1 , further comprising:
inserting, into a linked list, a plurality of elements each corresponding to one or more of the plurality of data packets and an associated signal quality; and
iterating through the linked list to identify a set of data packets for encapsulation and transmission based at least in part on a signal quality associated with each element of the linked list.
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 method of controlling the flow of data traffic for a broadcast signal implementing adaptive coding and modulation, the method comprising:
dynamically assigning a modcode of a plurality of modcodes to each of a plurality of data packets based at least in part on a signal quality of a link on which each respective packet is destined;
associating a timestamp with each of the plurality of data packets;
transmitting a subset of the plurality of data packets according to a defined order of progression, 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 modcode of the plurality of modcodes;
transmitting the first fragment according to a second modcode of the plurality of modcodes; and
transmitting the second fragment according to the first modcode, the first modcode of higher order than the second modcode; and
interrupting the defined order of progression upon expiration of a timer to transmit an out of order packet with a timestamp exceeding a first threshold age, wherein the out of order packet comprises one of the plurality of packets not included in the subset.
16. The method of claim 15 , wherein the first fragment is sized to fill a length of prospective pad for a frame to be transmitted according to the second modcode.
17. A device for controlling the flow of data traffic for a broadcast signal implementing adaptive coding and modulation, the device comprising:
a sorting unit configured to dynamically assign a different modcode to each of a plurality of packets based at least in part on a signal quality of a link on which each respective packet is to be received;
a transmitting unit, coupled with the sorting unit, and configured to:
transmit a subset of the plurality of packets according to a defined order of progression;
interrupt the defined order of progression upon expiration of a timer to transmit an out of order packet exceeding a threshold age, wherein the out of order packet comprises one of the plurality of packets not included in the subset;
transmit each data packet associated with a first modcode of the plurality of modcodes before incrementing to a next higher order second modcode of the plurality of modcodes; and
transmit a data packet with an oldest timestamp associated with the second modcode.
18. The device of claim 17 , wherein,
the sorting unit is further configured to block additional incoming data packets when the out of order packet exceeds a second threshold age.
19. The device of claim 18 , wherein,
the sorting unit is further configured to allow data packets associated with a threshold quality or class of service to enter.
20. The device of claim 17 , wherein,
the transmitting unit is further configured to restarting the defined order of progression from the out of order packet.
21. The device of claim 17 , wherein,
the transmitting unit is further configured to varying the period of the timer based at least in part on a latency associated with transmitting from the packet forwarding queues.
22. The device of claim 17 , wherein,
the transmitting unit is further configured to transmit at least one data packet associated with the first modcode and the data packet associated with the second modcode in a single frame according to the first modcode.
23. The device of claim 17 , wherein,
the sorting unit is configured to vary a signal quality range associated with one or more of the plurality of modcodes to modify a reliability margin for at least a subset of the plurality of data packets destined for a link within the varied signal quality range.