People have been working on software radio for about few years. Software radio is just what it sounds like - a radio that uses software to perform many of the signal processing tasks that analog circuits traditionally handle. Software radio could turn out to be a paradigm shift for communication systems. The US Defense Advanced Projects Research Agency (DARPA) kicked off research into software radios to solve military problems, but software radios can help solve some important problems in commercial communication systems as well. Software radio offers the advantage of putting many traditionally hard functions in modules whose characteristics can be changed while the radio is running.