Reed-Solomon erasure decoding with error detection for retransmission
View Patent ↗By utilizing Reed-Solomon erasure decoding algorithms and techniques, the system is able to perform error detection for the case where the number of bytes received in error exceeds a correcting capability of a decoder. The error detection can be used, for example, to determine whether a codeword is decodable, and whether the retransmission of data is necessary. The retransmission can be accomplished by assembling a message that is sent to another modem requesting retransmission of one or more portions of data, such as one or more codewords.
1. A method to determine a decodability of a codeword in a communications environment comprising:
assigning or obtaining reliability metrics for a plurality of bytes in the codeword; determining a score for a plurality of codeword decoding solutions based on the reliability metrics;
comparing the score to a correctability threshold;
determining whether the codeword is decodable; and
requesting retransmission of non-decodable codeword.
2. The method of claim 1 , further comprising performing the scoring a second time utilizing a byte-swapping technique.
3. The method of claim 2 , wherein the byte-swapping technique swaps R th and R+1 th worst bytes.
4. The method of claim 2 , further comprising sorting a plurality of reliability metrics.
5. The method of claim 1 , further comprising choosing a plurality of worst bytes as potential erasures.
6. The method of claim 1 , further comprising summing a plurality of reliability metrics for each byte that was incorrect for a particular solution.
7. The method of claim 1 , further comprising determining whether a scored codeword is less than the correctability threshold.
8. The method of claim 1 , wherein a decoding solution is one that minimizes an objective function based reliability of bytes corrected in a particular solution.
9. The method of claim 8 , wherein the decoding solution corresponds to different numbers of potential erasures, located at S least reliable codeword locations and T errors, wherein a location of the T errors is determined by a decoder.
10. The method of claim 1 , further comprising obtaining a list of metrics for R+1 worst bytes.
11. The method of claim 1 , further comprising measuring a mean metric for good frames.
12. The method of claim 1 , further comprising comparing or combining metrics from a first codeword with one or more retransmitted codewords.
13. The method of claim 1 , wherein the reliability metric is based on Viterbi path-metric information.
14. The method of claim 1 , further comprising forwarding information to a management entity indicating that the codeword was not correctable.
15. A system that determines a decodability of a codeword in a communications environment comprising:
an error detection module that determines a score for a plurality of codeword decoding solutions based on reliability metrics, the reliability metrics assigned or obtained for a plurality of bytes in the codeword;
a processor that compares the score to a correctability threshold and determines whether the codeword is decodable; and
a retransmission module that requests retransmission of a non-decodable codeword.
16. The system of claim 15 , wherein the error detection module performs the scoring a second time utilizing a byte-swapping technique.
17. The system of claim 15 , wherein a plurality of reliability metrics are sorted.
18. The system of claim 15 , wherein a plurality of worst bytes are chosen as potential erasures.
19. The system of claim 15 , wherein a plurality of reliability metrics are summed for each byte that was incorrect for a particular solution.
20. The system of claim 15 , wherein the error detection module further determines whether a scored codeword is less than the correctability threshold.
21. The system of claim 15 , wherein a decoding solution is one that minimizes an objective function based reliability of bytes corrected in a particular solution.
22. The system of claim 15 , wherein a list of metrics is obtained for R+1 worst bytes.
23. The system of claim 15 , wherein the error detection module further measures a mean metric for good frames.
24. The system of claim 15 , wherein metrics from a first codeword are compared or combined with one or more retransmitted codewords.
25. The system of claim 15 , wherein the reliability metric is based on Viterbi path-metric information.
26. The system of claim 15 , wherein the error detection module further forwards information to a management entity indicating that the codeword was not correctable.