Applications
Due to the simplicity of the channel encoding and decoding for repetition codes, they find applications in fading channels and non-AWGN environments. Repetition codes can be viewed as a method of space-time diversity as well.
Most modulation techniques transmit a bit or chip over many cycles of a sinusoid carrier signal. The low-pass filter used to average the relevant parameter (amplitude, phase, or frequency) over the entire bit-time or chip-time can be seen as a kind of repetition decoder.
Some UARTs, such as the ones used in the FlexRay protocol, use a majority filter to ignore brief noise spikes. This spike-rejection filter can be seen as a kind of repetition decoder.
Despite their poor performance as stand-alone codes, use in Turbo code-like iteratively decoded concatenated coding schemes, such as repeat-accumulate (RA) and accumulate-repeat-accumulate (ARA) codes, allows for surprisingly good error correction performance.
Repetition codes are one of the few known codes whose code rate can be automatically adjusted to varying channel capacity, by sending more or less parity information as required to overcome the channel noise, and it is the only such code known for non-erasure channels. Practical adaptive codes for erasure channels have been invented only recently, and are known as fountain codes.
Read more about this topic: Repetition Code