source coding theorem

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source coding theorem In communication theory, the statement that the output of any information source having entropy H units per symbol can be encoded into an alphabet having N symbols in such a way that the source symbols are represented by codewords having a weighted average length not less than H/logN

(where the base of the logarithm is consistent with the entropy units). Also, that this limit can be approached arbitrarily closely, for any source, by suitable choice of a variable-length code and the use of a sufficiently long extension of the source (see source coding).

The theorem was first expounded and proved by Claude Elwood Shannon in 1948.