Turbo code: Difference between revisions

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Turbo codes were so revolutionary at the time of their introduction that many experts in the field of coding did not believe the reported results. When the performance was confirmed a small revolution in the world of coding took place that led to the investigation of many other types of iterative signal processing.

The first class of turbo code was the parallel concatenated convolutional code (PCCC). Since the introduction of the original parallel turbo codes in 1993, many other classes of turbo code have been discovered, including serial versions [[serial concatenated convolutional codes]] and [[repeat-accumulate code]]s. Iterative turbo decoding methods have also been applied to more conventional FEC systems, including Reed-SolomonReed–Solomon corrected convolutional codes, although these systems are too complex for practical implementations of iterative decoders. Turbo equalization also flowed from the concept of turbo coding.

In addition to turbo codes, Berrou also invented recursive systematic convolutional (RSC) codes, which are used in the example implementation of turbo codes described in the patent. Turbo codes that use RSC codes seem to perform better than turbo codes that do not use RSC codes.

Prior to turbo codes, the best constructions were serial [[concatenated code]]s based on an outer [[Reed-SolomonReed–Solomon error correction]] code combined with an inner [[Viterbi algorithm|Viterbi-decoded]] short constraint length [[convolutional code]], also known as RSV codes.

In a later paper, Berrou gave credit to the intuition of "G. Battail, [[Joachim Hagenauer|J. Hagenauer]] and P. Hoeher, who, in the late 80s, highlighted the interest of probabilistic processing." He adds "[[Robert G. Gallager|R. Gallager]] and M. Tanner had already imagined coding and decoding techniques whose general principles are closely related," although the necessary calculations were impractical at that time.<ref>{{Citation|first=Claude|last=Berrou|title=The ten-year-old turbo codes are entering into service|___location=Bretagne, France|accessdate=11 February 2010|url=https://www.researchgate.net/publication/3199004}}</ref>