This book presents an inevitable evolution in today's wireless communication world: it concerns “cognitive radio” (CR). This new concept is based on the work of Joseph Mitola published in 1999 and 2000 [MIT 99a, MIT 00a].


From information theory to cognitive radio

In 1948, through a single 55-page publication, Claude Elwood Shannon [SHA 48] radically changed the vision of modern telecommunications by inventing a new theory known as Information Theory. In this publication, Shannon brought, in particular, the response to a fundamental telecommunications problem: how much information can be transferred between two people communicating in a given environment at a particular time, so that everyone understands the respective information without errors? Ever since the formulation of this response by Shannon, we see around us the development of phones, WiFi cards, etc., capable of transmitting more and more data per second. However, we must not delude ourselves, and it is in this that Shannon's work is so fundamental: the rate of information transmitted without error is naturally limited by the communication environment, the frequency band (commonly called bandwidth) used, and the power of transmitted signals. Hence, if any of these three fundamental resources reaches its limit, we cannot transmit information at a higher rate. Ten years ago, Joseph Mitola saw that a revolution in telecommunications was definitely going to take place right away. The principal perception ...

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