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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]] 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 codes]]<ref>Benedetto, Sergio, and Guido Montorsi. "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.
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