Coding and Information Theory
The aim of coding is to add redundant information to a message in order to correct errors introduced by the channel.
The code rate is a measure of how much redundancy is added to the message. Specifically a block code has rate
with K data bits and N bits in total.
The fundamental theorem of information theory states that the probability of codeword error will tend to zero (exponentially with blocklength) provided the code rate is less than the capacity of the channel.