To ensure that data is transmitted as error-free as possible, additional bits for forward error correction (FEC) are inserted during channel coding
. The ratio between the number of information bits and code bits is the code rate, typically denoted by the letter "R". If many redundancy bits are inserted, as in the convolutional
code, then the code rate is low because the number of code bits is high relative to the information bits. For example, if one additional redundancy bit is inserted for every three bits, then the code rate is R=3/4. The lower the code rate, the higher the code recovery. Thus, a code rate of R=1/2 provides higher code recovery than a code rate R=5/6.
Due to the additional redundancy bits, the code rate directly affects the data rate. A lower code rate with more redundancy bits inevitably results in a lower data rate. The effects are shown in the Modulation and Coding Scheme (MCS).