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In `F33f`_`[information theory`:/page/wikibook/entry.mu`zim=wikipedia_en_all_nopic_2025-08.zim|entry_path=Information_theory]`_`f, a `!soft-decision decoder`! is a kind of `F33f`_`[decoding method`:/page/wikibook/entry.mu`zim=wikipedia_en_all_nopic_2025-08.zim|entry_path=Decoding_methods]`_`f – a class of `F33f`_`[algorithm`:/page/wikibook/entry.mu`zim=wikipedia_en_all_nopic_2025-08.zim|entry_path=Algorithm]`_`f used to decode data that has been encoded with an `F33f`_`[error correcting code`:/page/wikibook/entry.mu`zim=wikipedia_en_all_nopic_2025-08.zim|entry_path=Error_correcting_code]`_`f. Whereas a `F33f`_`[hard-decision decoder`:/page/wikibook/entry.mu`zim=wikipedia_en_all_nopic_2025-08.zim|entry_path=Forward_error_correction]`_`f operates on data that take on a fixed set of possible values (typically 0 or 1 in a binary code), the inputs to a soft-decision decoder may take on a whole range of values in-between. This extra information indicates the reliability of each input data point, and is used to form better estimates of the original data. Therefore, a soft-decision decoder will typically perform better in the presence of corrupted data than its hard-decision counterpart.`:cite-ref-1[`F5bf`_`[1`#cite-note-1]`_`f]

Soft-decision decoders are often used in `F33f`_`[Viterbi decoders`:/page/wikibook/entry.mu`zim=wikipedia_en_all_nopic_2025-08.zim|entry_path=Viterbi_decoder]`_`f and `F33f`_`[turbo code`:/page/wikibook/entry.mu`zim=wikipedia_en_all_nopic_2025-08.zim|entry_path=Turbo_code]`_`f decoders.

>>Contents

• `F0af`_`[See also`#see-also]`_`f

• `F0af`_`[References`#references]`_`f

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>>See also

• `F33f`_`[Forward error correction`:/page/wikibook/entry.mu`zim=wikipedia_en_all_nopic_2025-08.zim|entry_path=Forward_error_correction]`_`f

• `F33f`_`[Soft-in soft-out decoder`:/page/wikibook/entry.mu`zim=wikipedia_en_all_nopic_2025-08.zim|entry_path=Soft-in_soft-out_decoder]`_`f

>>References

`:cite-note-1`!1.`! `F0af`_`[↑`#cite-ref-1]`_`f `:citerefproakis2001`aProakis, John (2001). `*Digital communications`* (4th ed.). McGraw Hill. pp. 457–460. `F33f`_`[ISBN`:/page/wikibook/entry.mu`zim=wikipedia_en_all_nopic_2025-08.zim|entry_path=ISBN_(identifier)]`_`f 0-07-118183-0.

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