Business telecommunications and IT systems

Error detection and correction is a technique which enables reliable delivery of digital data over unreliable communication channels.

Communication channels are often subject to noise which may introduce errors during transmission.

Error detection detects these errors and error correction reconstructs the original data.

There are two main methods involved,

i) Automatic Repeat Request (ARQ) (also known as backward error correction). An error control technique which requests retransmission of the erroneous data. Every block of data received is checked using the error detection code used, and if the check fails, retransmission of the data is requested repeatedly until the data can be verified.

ii) Forward Error Correction (FEC). The sender encodes the data using an error correcting code (ECC) prior to transmission. The additional information added by the code is used by the receiver to recover the original data. In this case, the reconstructed data is deemed to be the "most likely" original data.

ARQ and FEC are sometimes combined such that minor errors are corrected without retransmission whereas major errors are corrected with a request for retransmission.

This is called hybrid automatic repeat-request (HARQ).