Redundancy

The inclusion of duplicate or alternate system elements to improve operational reliability by ensuring continued operation in the event that a primary element fails.

The duplication of information or hardware equipment components to ensure that should a primary resource fail, a secondary resource can take over its function.

In the transmission of data, the excess of transmitted message symbols over that required to convey the essential information in a noise-free circuit. Note: Redundancy may be introduced intentionally (as in the case of error detection or correction codes) or inadvertently (such as by oversampling a band-limited signal, inefficient formats, etc.). 2. In a communication system, surplus capability usually provided to improve the reliability and quality of service.