Nowadays, depending on the purpose, the geographical region, the
particular carrier, and many other factors, the electromagnetic spectrum
assigned to wireless networks is controlled by governmental agencies.
Increasing demands on the radio spectrum have driven wireless engineers
to rethink approaches by which devices should access this natural, and
arguably scarce, resource. Cognitive Radio has arisen as a new wireless
communication paradigm aimed at solving the spectrum underutilization
problem. In this book, the authors explore a novel variety of techniques
aimed to find unused portions of the electromagnetic spectrum and take
advantage of them in an opportunistic manner.