When an error is discovered the receiver is able to ask the sender to retransmit the entire data unit

Error Correction-Forward Error Correction

• A receiver is able to use an error-correcting code which automatically corrects certain errors
• Single-bit errors
• Is able to be detected by the addition of parity bit which helps to find "error" or "no error" which is sufficient to detect errors
• To correct errors the receiver is able to simply invert 0 to 1 or 1 to 0 but the problem is "locating" the position of error
• To do thus requires enough redundancy bits
• Condition: 2r >= m + r + 1