Forward Error Correction is a process of adding redundant bits to the data to be transmitted. During the transmission, data may get corrupted by interference (changes from 0 to 1 / 1 to 0). These error correction bits are used at the receivers for restoring corrupted bits.
The Code Rate of a forward error correction expresses the proportion of bits in a data stream that actually carry useful information.
There are 4 code rates used in LoRaWAN:
For example, if the code rate is 5/7, for every 5 bits of useful information, the coder generates a total of 7 bits of data, of which 2 bits are redundant.
Any Code Rate is usually applied with a spreading factor. For example, if you applied the code rate 4/5 with the Spreading Factor 7 theoretically 7 x 4/5 = 5.6 bits carry useful information and the remaining 1.4 bits are used for forward error correction.
Spreading factor 7 = the number of bits a symbol can encode is 7.
If you add more error correction bits to your information will increase the Time-On-Air and decrease the battery life.