Traditional radio chips are hard-wired to communicate using one specific protocol. For example, a typical cell phone has several different chips to handle a variety of radio communications: one to talk to cell phone towers, another to contact WiFi base stations, a third to receive GPS signals, and a fourth to communicate with Bluetooth devices. In contrast, software-defined radio hardware works with raw electromagnetic signals, relying on software to implement specific applications.
Software-defined radio can increase the rate of advance of wireless technologies and bring interesting combinations of radios and functionalities to the same chips and the same devices.