Communications Technology Handbook, 2nd Edition

11 Error control

The technique of forward error control (FEC) is so called because the means of detecting or correcting bit errors in a digital system during transmission over a noisy channel is contained within the transmitted message stream. This is achieved by the addition of extra redundant bits which, when suitably processed, are capable of identifying errors. The alternative technique involves scanning the received bit stream to make a running check of the disparity (see also Codes and coding formats, p. 59) and if an error is detected, automatically generate a request for a repeat transmission of the bytes in error (Van Duuren’s ARQ, automatic request repeat). Either method makes additional demands upon the spectrum: FEC requires additional ...