Cognitive Radios for Spectrum Sharing
Anant Sahai, Shridhar Mubaraq Mishra, Rahul Tandra, Kristen Ann Woyach · 2009
Wireless systems require spectrum to operate, but interference is likely if radios in physical proximity simultaneously operate on the same band. Therefore, spectrum is a potentially scarce resource; across the planet today, spectrum is regulated so that most bands are allocated exclusively to a single system licensed to use that band in any given location. However, such static spectrum allocation policies lead to significant underuse of spectrum [1]. This can be viewed as a kind of regulatory overhead that is paid to get reliable operation. With frequency-agile radios becoming commercially feasible within the next 5-10 years, Cognitive Radio is about making such radios smart enough to share spectrum and reduce the regulatory overhead. This is an impending wireless revolution that draws upon many signal-processing areas including robust detection, sensor networks, as well as the design of incentives and waveforms. This is a short column touching on the issues; further technical details/references can be found in [2]. THE OPPORTUNITY IN THE TELEVISION BANDS Right now, there is significant excitement surrounding the broadcast television bands. The Federal Communications Commission (FCC) has started considering dynamic approaches for spectrum sharing and the IEEE has launched the 802.22 standards process to use TV-band spectrum holes for enabling wide-area Internet service [3], [4]. This context is illustrated in Figure 1.