Editing Convolutional code (section)

== History ==
Convolutional codes were introduced in 1955 by [[Peter Elias]]. It was thought that convolutional codes could be decoded with arbitrary quality at the expense of computation and delay. In 1967, [[Andrew Viterbi]] determined that convolutional codes could be maximum-likelihood decoded with reasonable complexity using time invariant trellis based decoders — the [[Viterbi algorithm]]. Other trellis-based decoder algorithms were later developed, including the [[BCJR algorithm|BCJR]] decoding algorithm.

Recursive systematic convolutional codes were invented by [[Claude Berrou]] around 1991. These codes proved especially useful for iterative processing including the processing of concatenated codes such as [[Turbo code|turbo codes]].<ref>Benedetto, Sergio, and Guido Montorsi. "[https://web.archive.org/web/20190406181758/https://ieeexplore.ieee.org/abstract/document/390945/ Role of recursive convolutional codes in turbo codes]." Electronics Letters 31.11 (1995): 858-859.</ref>

Using the "convolutional" terminology, a classic convolutional code might be considered a [[Finite impulse response]] (FIR) filter, while a recursive convolutional code might be considered an [[Infinite impulse response]] (IIR) filter.