Concatenated error correction code: Difference between revisions

Revision as of 15:53, 5 February 2010

Revision as of 15:56, 5 February 2010

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Concatenated codes were first implemented for [[deep space]] communication in the [[Voyager program]] after the craft had finished their encounters with the outer Gas Giants.<ref name="deep-space-codes">K. Andrews et al., ''The Development of Turbo and LDPC Codes for Deep-Space Applications'', Proceedings of the IEEE, Vol. 95, No. 11, Nov. 2007.</ref> Since then, concatenated codes became the workhorse for efficient error correction coding, and stayed so at least until the invention of [[turbo codes]] and [[LDPC codes]].

'''Inner codeCode : short blocks''' <br>

Typically, the inner code is not a block code but a soft-decision [[convolutional code|convolutional]] [[Viterbi decoder|Viterbi-decoded]] code with a short constraint length. For the outer code, a longer hard-decision block code, frequently [[Reed Solomon]] with 8-bit symbols, is selected.

'''Outer codeCode : long blocks''' <br>

The larger symbol size of the Outer Code makes the outer code more robust to [[error burst|burst error]]s that may occur due to channel impairments,. andAnd because erroneous output of the convolutional code itself is typically bursty. Additionally, an [[interleaving]] layer may be used that spreads burst errors across a wider range.

The combination of an inner ''Viterbi convolutional code'' with an outer ''Reed-Solomon code'' (known as an RSV code) became the most popular construction use of code concatenation.