Timeline for Error correcting codes obtained as superposition of two codes e.g. CRC+Convolutional
Current License: CC BY-SA 3.0
7 events
| when toggle format | what | by | license | comment | |
|---|---|---|---|---|---|
| Aug 6, 2012 at 10:19 | comment | added | Alexander Chervov | Thank you! Does concatenation exactly means what I mentioned? | |
| Aug 6, 2012 at 10:06 | comment | added | Jyrki Lahtonen | Alexander: I forgot to say that "concatenation" of codes (instead of "superposition") is the standard term. So you may have better luck searching for more information using "concatenated codes" as a buzzword. The combinations that I have seen are convolutional+algebraic (such as here) or LDPC+algebraic. An algebraic code is a common choice as the last code, because they can effectively deal with a small number of errors, but are bad at dealing with soft errors. The code exposed to the horrors of radio propagation should always be able to deal with soft errors. | |
| Jul 24, 2012 at 7:26 | vote | accept | Alexander Chervov | ||
| Jul 11, 2012 at 7:32 | comment | added | Alexander Chervov | @Jyrki thank you very much ! I'll try but it takes time I am novice. By the way I just understood the following problem with List Viterbi - it does NOT create optimal list (at least in theory), I mean of course Viterbi best path is optimal paths, but second path in list may not be actually second path in true list - the reason is that all members in the list will be more or less the same at the initial N-(6*TrellisLen) bits... So it seems to me that List Viterbi have some space of improvement | |
| Jul 11, 2012 at 6:44 | comment | added | Jyrki Lahtonen | Your CRC can correct a single error (syndrome look up), which is a live possibility, if the Viterbi output has an odd weight (all the words that pass the CRC have an even weight). You can further improve upon that by trying Forney's soft decision decoding (if you have SOVA output at hand): try the effect of swapping one or two (according to the parity) least reliable bits, and see, if you can now correct a remaining error by syndrome look up. Forney had a more general scheme, but as your CRC can only correct a single error, I think his algorithm amounts to just that. | |
| Jul 10, 2012 at 8:22 | answer | added | Jyrki Lahtonen | timeline score: 2 | |
| Jul 10, 2012 at 6:07 | history | asked | Alexander Chervov | CC BY-SA 3.0 |