Forward error correction with channel adaptation

• US 20020188908A1
• Filed: 05/23/2002
• Published: 12/12/2002
• Est. Priority Date: 12/06/1999
• Status: Active Grant

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Intellon Corporation (Qualcomm, Inc.)
• Inventors: Yonge, Lawrence W. III, Blanchard, Bart W., Mashburn, Harper Brent, Gargrave, Timothy Robert, Lawton, William Edward
• Granted Patent: US 6,553,534 B2
• Time in Patent Office: Days
• US Class Current: 714/779
• 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 1/0021 in which the algorithm uses adaptive thresholds
• CPC Class Codes: H04L 1/0025 Transmission of mode-switching indication
• CPC Class Codes: H04L 1/0057 Block codes H04L1/0061, H04L1/0064 take precedence
• CPC Class Codes: H04L 1/0059 Convolutional codes
• CPC Class Codes: H04L 1/0071 Use of interleaving interleaving per se H03M13/27
• CPC Class Codes: H04L 5/0044 allocation of payload

Abstract

A scheme for configuring an FEC encoder (including an associated interleaver) for changing data channel characteristics. Channel information specifying a modulation mode and carriers capable of supporting the modulation mode for the data channel is received by a transmitting network node for use in a data transmission to a receiving network node. The received channel information is based on a prior data transmission to the receiving network node over the data channel. Configuration values are computed from the received channel information and an amount of data to be transmitted in a data transmission. The FEC encoder is configured to operate on the data transmission data amount according to the configuration information.

Claims

1. A method of adapting a forward error correction (FEC) encoder to a channel over which data encoded by the FEC encoder and modulated onto OFDM symbols is to be transmitted in a data transmission to a receiving network node, comprising:

receiving channel information for specifying symbol block sizes associated with the data transmission, the received channel information being based on a prior data transmission to the receiving network node;

computing FEC encoder configuration information based on the received channel information; and

configuring the FEC encoder to operate on the data according to the configuration information.

2. The method of claim 1, wherein the received channel information is based on characteristics of the channel.

3. The method of claim 2, wherein the received channel information includes a modulation type and carriers capable of supporting the modulation type for the channel.

4. The method of claim 3, wherein the symbol block sizes include a fixed size and a variable size and wherein computing FEC encoder configuration values comprises:

determining from the channel information a number of symbol blocks of the fixed size and a number of remaining data bytes to be included in a last symbol block of the variable size; and

computing a number of symbols for transmitting the remaining data bytes from the number of remaining data bytes, the channel information and a code block size associated with the FEC encoder.

5. The method of claim 4, wherein the FEC encoder includes an interleaver and configuring comprises:

configuring the interleaver to store the last variable size symbol block of encoded data based on the computed number of symbols and the channel information.

6. The method of claim 5, wherein computing the number of symbols comprises:

computing a number of Reed-Solomon blocks based on the computed remaining number of bytes and a maximum number of information bytes in a Reed-Solomon block of data;

computing a Reed-Solomon block size based on the remaining number of bytes and the number of Reed-Solomon blocks; and

computing the total number of bits to be modulated on the symbols after coding from the computed number of Reed-Solomon blocks and block size.

7. The method of claim 6, wherein the FEC encoder includes a Reed-Solomon encoder and computing further comprises:

computing a maximum number of Reed-Solomon bytes in the last variable size symbol block; and

computing a Reed-Solomon block size based on the maximum number of Reed-Solomon bytes in the last variable size block.

8. The method of claim 7, wherein the FEC encoder includes a convolutional encoder and wherein computing the maximum number of Reed-Solomon bytes comprises:

computing a total number of bits to be encoded from the channel information;

subtracting a number of tail bits employed by the convolutional encoder from the total number of bits to be encoded to produce a difference value; and

dividing the difference value by eight.

9. The method of claim 7, wherein computing the Reed-Solomon block size comprises:

using the maximum number of Reed-Solomon bytes to compute a number of Reed-Solomon blocks in the last variable size symbol block;

finding a quotient value equal to the maximum number of Reed-Solomon bytes divided by the number of Reed-Solomon blocks in the last variable size symbol block;

rounding off the quotient value to the next lowest whole number as a new quotient value; and

choosing the smaller of the new quotient value and the a maximum block size associated with the Reed-Solomon encoder.

10. The method of claim 7, wherein configuring configures the Reed-Solomon encoder to operate according to the computed number of RS blocks and the RS block size.

11. The method of claim 1, wherein the received channel information comprises a channel map associated with the modulation type.

12. The method of claim 11, wherein the channel map identifies the carriers for supporting the modulation type with which the channel map is associated.

15. The computer program of claim 14, wherein the received channel information is based on characteristics of the channel.

16. The computer program of claim 15, wherein the received channel information includes a modulation type and carriers capable of supporting the modulation type for the channel.

17. The computer program of claim 16, wherein the symbol block sizes include a fixed size and a variable size and wherein the instructions for computing FEC encoder configuration values comprise instructions causing the computer to:

determine from the channel information a number of symbol blocks of the fixed size and a number of remaining data bytes to be included in a last symbol block of the variable size; and

compute a number of symbols for transmitting the remaining data bytes from the number of remaining data bytes, the channel information and a code block size associated with the FEC encoder.

18. The computer program of claim 17, wherein the FEC encoder includes an interleaver and the instructions for configuring comprise instructions causing the computer to:

configure the interleaver to store the last variable size symbol block of encoded data based on the computed number of symbols and the channel information.

19. The computer program of claim 18, wherein the instructions for computing the number of symbols comprise instructions causing the computer to:

compute a number of Reed-Solomon blocks based on the computed remaining number of bytes and a maximum number of information bytes in a Reed-Solomon block of data;

compute a Reed-Solomon block size based on the remaining number of bytes and the number of Reed-Solomon blocks; and

compute the total number of bits to be modulated on the symbols after coding from the computed number of Reed-Solomon blocks and block size.

20. The computer program of claim 19, wherein the FEC encoder includes a Reed-Solomon encoder and the instructions for computing further comprise instructions causing the computer to:

compute a maximum number of Reed-Solomon bytes in the last variable size symbol block; and

compute a Reed-Solomon block size based on the maximum number of Reed-Solomon bytes in the last variable size block.

21. The computer program of claim 20, wherein the FEC encoder includes a convolutional encoder and wherein the instructions for computing the maximum number of Reed-Solomon bytes comprise instructions causing the computer to:

compute a total number of bits to be encoded from the channel information;

subtract a number of tail bits employed by the convolutional encoder from the total number of bits to be encoded to produce a difference value; and

divide the difference value by eight.

22. The computer program of claim 20, wherein the instructions for computing the Reed-Solomon block size comprise instructions causing the computer to:

use the maximum number of Reed-Solomon bytes to compute a number of Reed-Solomon blocks in the last variable size symbol block;

find a quotient value equal to the maximum number of Reed-Solomon bytes divided by the number of Reed-Solomon blocks in the last variable size symbol block;

round off the quotient value to the next lowest whole number as a new quotient value; and

choose the smaller of the new quotient value and the a maximum block size associated with the Reed-Solomon encoder.

23. The computer program of claim 20, wherein the instructions for configuring further comprise instructions causing the computer to:

configure the Reed-Solomon encoder to operate according to the computed number of RS blocks and the RS block size.

24. The computer program of claim 14, wherein the received channel information comprises a channel map associated with the modulation type.

25. The computer program of claim 24, wherein the channel map identifies the carriers for supporting the modulation type with which the channel map is associated.

13. A method of adapting a forward error correction (FEC) encoder and an interleaver to a channel over which data encoded by the FEC encoder and modulated onto OFDM symbols is to be transmitted in a data transmission to a receiving network node, comprising:

receiving channel information for specifying symbol block sizes associated with the data transmission, the received channel information being based on a prior data transmission to the receiving network node;

computing FEC encoder and interleaver configuration information based on the received channel information; and

configuring the FEC encoder and interleaver to operate on the data according to the configuration information.

14. A computer program residing on a computer-readable medium for adapting a forward error correction (FEC) encoder to a channel over which data encoded by the FEC encoder and modulated onto OFDM symbols is to be transmitted in a data transmission to a receiving network node, the computer program comprising instructions causing a computer to:

receive channel information for specifying symbol block sizes associated with the data transmission, the received channel information being based on a prior data transmission to the receiving network node;

compute FEC encoder configuration information based on the received channel information; and

configure the FEC encoder to operate on the data according to the configuration information.

26. An apparatus for adapting a forward error correction (FEC) encoder to a channel over which data encoded by the FEC encoder and modulated onto OFDM symbols is to be transmitted in a data transmission to a receiving network node, comprising:

a transmit configuration unit for receiving channel information specifying symbol block sizes associated with the data transmission, the received channel information being based on a prior data transmission to the receiving network node, the transmit configuration unit computing FEC encoder configuration information based on the received channel information; and

a controller coupled to the transmit configuration unit and the FEC encoder for configuring the FEC encoder to operate on the data according to the configuration information.

27. An apparatus for adapting a forward error correction (FEC) encoder to a channel over which data encoded by the FEC encoder and modulated onto OFDM symbols is to be transmitted in a data transmission to a receiving network node, comprising:

means for receiving channel information specifying symbol block sizes associated with the data transmission, the received channel information being based on a prior data transmission to the receiving network node;

means for computing FEC encoder configuration values based on the received channel information; and

means for configuring the FEC encoder to operate on the data according to the configuration information.