Concatenated error correction code: Difference between revisions

Revision as of 15:41, 5 February 2010

Revision as of 15:43, 5 February 2010

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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. The larger symbol size makes the outer code more robust to [[error burst|burst error]]s that may occur due to channel impairments, and because erroneous output of the convolutional code itself is 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, and was already used on the Voyager probes. ItConcatenated codes isare still in use today for deep-space and [[satellite communication]], notably the [[DVB-S]] [[digital television]] broadcast standard.

In a more loose sense, any (serial) combination of two or more codes may be referred to as a concatenated code. For example, within the [[DVB-S2]] standard, a highly efficient [[LDPC code]] is combined with an algebraic outer code in order to remove any resilient errors left over from the inner LDPC code due to its inherent [[error floor]].