Concatenated error correction code: Difference between revisions

Revision as of 15:43, 5 February 2010

Revision as of 15:47, 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, use of code concatenation. The uptake and waspopularization alreadyof usedthe onRSV code and its use in the Voyager probesProgram were somewhat simultainious. Concatenated codes are 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]].