Erasure code: Difference between revisions

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Revision as of 03:27, 18 May 2006

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'''Optimal erasure codes''' produce ''n/r'' blocks where any ''n'' blocks is sufficient to recover the original message. Unfortunately optimal codes are costly (in terms of memory usage, CPU time or both) and so ''near optimal erasure codes'' are often used. These require (1+ε)''n'' blocks to recover the message. Reducing ε can be done at the cost of CPU time.

[[Fountain codescode]]s (also known as '''Rateless erasure codes''', e.g., see [http://www.ewh.ieee.org/soc/icss/advances4.html#Item4 here]) transform an ''n'' block message into a practically infinite encoded form. Encoded symbols can be generated ad infinitum and some number of them is enough to recover the message.

==Examples==