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Emvee~enwiki (talk | contribs) Also Low-density parity-check codes come very close to the Shannon limit. +soft bit |
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'''Turbo codes''' are a class of recently-developed high-performance [[error-correcting code|error correction codes]] finding use in deep-space [[satellite]] [[communications]] and other applications where designers seek to achieve maximal information transfer over a limited-bandwidth communication link in the presence of data-corrupting noise. Of all practical error correction methods known to date, turbo codes, together with [[Low-density parity-check code]]s, come closest to approaching the [[Shannon limit]], the theoretical limit of maximum information transfer rate over a noisy channel.
The method was introduced by [[Claude Berrou|Berrou]], [[Alain Glavieux|Glavieux]], and [[Punya Thitimajshima|Thitimajshima]] in their [[1993]] paper: "''Near Shannon Limit error-correcting coding and decoding: Turbo-codes''" published in the Proceedings of IEEE International Communications Conference [http://www-elec.enst-bretagne.fr/equipe/berrou/Near%20Shannon%20Limit%20Error.pdf]. Turbo code refinements and implementation are an area of active research at a number of universities.
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===The decoder===
The decoder front-end produces an integer for each bit in the data stream. This integer is a measure of how likely it is that the bit is a 0 or 1 and is also called ''soft bit''. The integer could be drawn from the range [-127, 127], where:
* -127 means "certainly 0"
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