In telecommunication and information theory, the code rate (or information rate) 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 k bits of useful information, the coder generates totally n bits of data, of which n-k are redundant.
For example: The code rate of a convolutional code may typically be 1/2, 2/3, 3/4, 5/6, 7/8, etc., corresponding to that one redundant bit is inserted after every single, second, third, etc., bit. The code rate of the Reed Solomon block code denoted RS(204,188) is 188/204, corresponding to that 204 - 188 = 16 redundant bits are added to each block of 188 bits of useful information.
A few error correction codes do not have a fixed code rate—rateless erasure codes.
- Huffman, W. Cary, and Pless, Vera, Fundamentals of Error-Correcting Codes, Cambridge, 2003.
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