Turbo code: Difference between revisions

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In [[information theory]], '''turbo codes''' (originally in French ''Turbocodes'') are a class of high-performance [[forward error correction]] (FEC) codes developed around 1990–91, but first published in 1993. They were the first practical codes to closely approach the maximum channel capacity or [[Shannon–Hartley theorem|Shannon limit]], a theoretical maximum for the [[code rate]] at which reliable communication is still possible given a specific noise level. Turbo codes are used in [[3G]]/[[4G]] mobile communications (e.g., in [[UMTS]] and [[LTE (telecommunication)|LTE]]) and in ([[Deep Space Network|deep space]]) [[satellite]] [[telecommunication|communications]] as well as other applications where designers seek to achieve reliable information transfer over bandwidth- or latency-constrained communication links in the presence of data-corrupting noise. Turbo codes compete with [[Low-density parity-check code|low-density parity-check]] (LDPC) codes, which provide similar performance (but wereare patent-free).<ref name="Closing">{{cite journal |author=Erico Guizzo |title=CLOSING IN ON THE PERFECT CODE |journal=IEEE Spectrum |date=Mar 1, 2004 |url=https://spectrum.ieee.org/closing-in-on-the-perfect-code}} "Another advantage, perhaps the biggest of all, is that the LDPC patents have expired, so companies can use them without having to pay for intellectual-property rights."</ref>

The name "turbo code" arose from the feedback loop used during normal turbo code decoding, which was analogized to the exhaust feedback used for engine [[turbocharging]]. [[Joachim Hagenauer|Hagenauer]] has argued the term turbo code is a misnomer since there is no feedback involved in the encoding process.<ref>{{cite journal |url=http://www.ima.umn.edu/csg/bib/bib16.0429hage.pdf |first1=Joachim |last1=Hagenauer |title=Iterative Decoding of Binary Block and Convolutional Codes |accessdate=20 March 2014 |url-status=dead |archiveurl=https://web.archive.org/web/20130611235418/http://www.ima.umn.edu/csg/bib/bib16.0429hage.pdf |archivedate=11 June 2013 |first2=Elke |last2=Offer |first3=Luiz |last3=Papke |volume=42 |issue=2 |date=March 1996 |journal=IEEE Transactions on Information Theory|pages=429–445 |doi=10.1109/18.485714 }}</ref>