Английская Википедия:Code rate
In telecommunication and information theory, the code rate (or information rate[1]) 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 <math>k/n</math> for every Шаблон:Mvar bits of useful information, the coder generates a total of Шаблон:Mvar bits of data, of which <math>n-k</math> are redundant.
If Шаблон:Mvar 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 <math>\leq R \cdot k/n</math>.
For example: The code rate of a convolutional code will typically be Шаблон:1/2, Шаблон:2/3, Шаблон:3/4, Шаблон:Frac, Шаблон:Frac, 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 Шаблон:Math 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
References
- ↑ Huffman, W. Cary, and Pless, Vera, Fundamentals of Error-Correcting Codes, Cambridge, 2003.
