Concatenated error correction codes

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The Compact Disc and Voyager Program spacecraft use concatenated error correction technologies. Concatenated error codes may have been introduced with spacecraft missions that were involved with mapping the Moon and Mars. In typical telecommunications systems before these data intensive missions -- only one hard error correction layer was used.

Concatenating error correction methods is useful in cases where the telecommunications link may be problematical. Typically a soft inner code (Viterbi) is used concatenated to a hard outer code (Reed-Solomon).

[edit] How it works

Inner code vs outer code performance

• typically the inner code is a weaker (and simpler) error correction code
• the outer correction code may not be in the same family of codes as the inner codes -- this is true for Voyager Program codes

[edit] Turbo codes, a compromise

Turbo codes, although not concatenated codes -- do typically utilise two different error correction codes running in parallel.

Concatenating codes can provide performance near that of Turbo codes but with an increase in decoder complexity.