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{{Short description|Non-redundant proportion of an error correction code data stream}}{{one source |date=April 2024}}File:Coderateblock.png|400px|thumb|right|Different code rates (Hamming codeHamming codeIn telecommunication and information theory, the code rate (or information rateHuffman, W. Cary, and Pless, Vera, Fundamentals of Error-Correcting Codes, Cambridge, 2003.) of a forward error correction code is the proportion of the data-stream that is useful (non-redundant). That is, if the code rate is k/n for every {{mvar|k}} bits of useful information, the coder generates a total of {{mvar|n}} bits of data, of which n-k are redundant. If {{mvar|R}} is the gross bit rate or data signalling rate (inclusive of redundant error coding), the net bit rate (the useful bit rate exclusive of error correction codes) is leq R cdot k/n. For example: The code rate of a convolutional code will typically be {{1/2}}, {{2/3}}, {{3/4}}, {{frac|5|6}}, {{frac|7|8}}, etc., corresponding to one redundant bit inserted after every single, second, third, etc., bit. The code rate of the octet oriented Reed Solomon block code denoted RS(204,188) is 188/204, meaning that {{math|1=204 − 188 = 16}} redundant octets (or bytes) are added to each block of 188 octets of useful information. A few error correction codes do not have a fixed code rate—rateless erasure codes.Note that bit/s is a more widespread unit of measurement for the information rate, implying that it is synonymous with net bit rate or useful bit rate exclusive of error-correction codes.

See also

• Entropy rate
• Information rate
• Punctured code

References

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