Page "Information theory" Paragraph 74

This capacity has the following property related to communicating at information rate R ( where R is usually bits per symbol ).

For any information rate R < C and coding error ε > 0, for large enough N, there exists a code of length N and rate ≥ R and a decoding algorithm, such that the maximal probability of block error is ≤ ε ; that is, it is always possible to transmit with arbitrarily small block error.

In addition, for any rate R > C, it is impossible to transmit with arbitrarily small block error.