
In
telecommunication
Telecommunication, often used in its plural form or abbreviated as telecom, is the transmission of information over a distance using electronic means, typically through cables, radio waves, or other communication technologies. These means of ...
and
information theory
Information theory is the mathematical study of the quantification (science), quantification, Data storage, storage, and telecommunications, communication of information. The field was established and formalized by Claude Shannon in the 1940s, ...
, the code rate (or information rate
[Huffman, 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
for every bits of useful information, the coder generates a total of bits of data, of which
are redundant.
If 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
.
For example: The code rate of a
convolutional code will typically be , , , , , 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 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
A unit of measurement, or unit of measure, is a definite magnitude (mathematics), magnitude of a quantity, defined and adopted by convention or by law, that is used as a standard for measurement of the same kind of quantity. Any other qua ...
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
Information theory
Rates
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