**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:

- 4/5
- 4/6
- 5/7
- 4/8

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.