Talk:Low-density parity-check code: Difference between revisions

Revision as of 19:01, 8 June 2009

Revision as of 19:34, 8 June 2009

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:::: does "sqrt_d(k) ones per column" makes a matrix sparse?

::::: since sqrt(k)/k approaches 0 with k->infinity, I would say, yes, they are sparse... but that's just my opinion.

:::::: AreI youthink surethe that'snumber right? By my working, we have for e.g. a 2D (square) code, there are <math>kd + (n-k) = dk + 2\sqrt{k}</math>of ones inper thecolumn parity-check matrix, and there are <math>n = k + 2\sqrt{k}</math> columns. From that,is <math>\lim_{k\rightarrow \infty} \frac{dk + 2\sqrt{k}}{k + 2\sqrt{k}} = d</math>. (Note that I'm tired, so I could easily have screwed up... [[User:Oli Filth|Oli Filth]]^{([[User talk:Oli Filth|talk]]<nowiki>|</nowiki>[[Special:Contributions/Oli_Filth|contribs]])} 19:01, 8 June 2009 (UTC)

:::::: Your threshold for sparsity seems to be based on the number of ones divided by the overall number of elements (''n''.''k''). This sounds fair enough, but wouldn't this classify most codes as sparse (e.g. Hamming)? [[User:Oli Filth|Oli Filth]]^{([[User talk:Oli Filth|talk]]<nowiki>|</nowiki>[[Special:Contributions/Oli_Filth|contribs]])} 19:01, 8 June 2009 (UTC)

:::: I think that LDPC are also characterized by there ability to be efficiently decoded by a low complexity iterative decoding algorithm. [[User:Cunchem|Cunchem]] ([[User talk:Cunchem|talk]]) 14:54, 8 June 2009 (UTC)