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Error correction is the process of detecting errors in transmitted messages and reconstructing the original error-free data. Error correction ensures that corrected and error-free messages are obtained at the receiver side.
Systems capable of requesting the retransmission of bad messages in response to error detection include an automatic request for retransmission, or automatic repeat request (ARQ) processing, in their communication software package. They use acknowledgments, negative acknowledgment messages and timeouts to achieve better data transmission.
ARQ is an error control (error correction) method that uses error-detection codes and positive and negative acknowledgments. When the transmitter either receives a negative acknowledgment or a timeout happens before acknowledgment is received, the ARQ makes the transmitter resend the message.
Error-correcting code (ECC) or forward error correction (FEC) is a method that involves adding parity data bits to the message. These parity bits will be read by the receiver to determine whether an error happened during transmission or storage. In this case, the receiver checks and corrects errors when they occur. It does not ask the transmitter to resend the frame or message.
A hybrid method that combines both ARQ and FEC functionality is also used for error correction. In this case, the receiver asks for retransmission only if the parity data bits are not enough for successful error detection and correction.