In 1992, Joe Mitola introduced the Software Defined Radio (SDR) concept to the world. This new concept uses software instead of hardware to process signals which are sent through antennas, in various frequencies. SDR is specially needed when there are applications that use multiple bands, reducing the number of hardware components and This section introduces the main elements of SDR, including USRP, daughterboards (hardware components), GNURadio, block types and some software tools.