A software-defined radio (SDR) is a radio communication system where components that have been typically implemented in hardware (e.g. mixers, filters, amplifiers, modulators/demodulators, detectors, etc.) are instead implemented by means of software on a personal computer or embedded system.
Some of the emerging trends in Software-Defined Radio include the use of cognitive radio, the use of software-defined radios for spectrum sensing, and the use of software-defined radios for spectrum management.