Error control coding incorporates information into the signal that allows a receiver to find and correct bit errors occurring in transmission and storage. Since such coding detects or corrects errors incurred in the communication or storage channel, it is often referred to as channel coding.
Recent advances in SP have allowed us to achieve performance on certain communication channels near the theoretical limit characterized by information theory. These successes were attained using advances in adaptive channel equalization, error correction coding, modulation techniques, and joint coding/modulation such as trellis coded modulation, where the error control coding is combined with efficient modulation techniques. High speed transmission over the local telephone loop and hence the potential for universal high-bandwidth access to the NII from homes depends on such high speed SP. This again shows the power of SP theory, algorithms, and technology in solving a real need for the NII.
Channel coding for fixed channels is a relatively mature field, but coding for time varying channels is a relatively young and immature field. Such channels are increasingly important, as exemplified by the wireless channel used for personal communication systems which are beginning to access the NII.
Channel coding for storage has also been very successful in boosting capacity, and remains a topic of active research. Much of the error control necessary for CDROM capacities was adapted from space communications technology, and the coding for rewritable CD's advances the SP devised for magnetic recording.