Signal Processing Techniques for Spectrum Sensing and Communication in Cognitive Radio Networks, Behrouz Farhang-Boroujeny, University of Utah

As the vast majority of the available spectral resources have already been licensed, it appears that there is little or no room to add any new services, unless some of the existing licenses are discontinued. On the other hand, studies have shown that vast portions of the licensed spectra are rarely used. This has initiated the idea of Cognitive Radios (CR) where secondary (i.e. unlicensed) users are allowed to transmit and receive data over portions of spectra when primary (i.e. licensed) users are inactive. This should be done in a way that the secondary users (SU) are invisible to the primary users (PU). The FCC Spectrum Policy Task force has already set the rules for the operation of CR networks. Standards working groups, e.g. IEEE802.22, have already been formed and are already working on relevant documents or have finalized the standards. This tutorial after presenting a review of the state of the art in cognitive radios, addresses a range of signal processing tools that are available for both spectral sensing and communications. In particular, the limitations of OFDM in cognitive radio settings are emphasized and less traditional multi-carrier techniques are emphasized.