Signal Processing for Cognitive Radios

9WIDEBAND SPECTRUM SENSING

9.1 INTRODUCTION

As noted in Chapter 3, the early focus of cognitive radios was mostly directed at achieving DSS and improving the spectrum utilization [15, 127], as opposed to more general definition of the concept envisioned in [1, 20]. However, in recent years, the focus of research on cognitive radios has returned to its original emphasis: radios that are, simply, cognitive or, more accurately, radios that are intelligent and cognitive [15, 16, 128]. While various forms of DSS for improving wireless spectrum utilization still remain an important application area, there is a growing recognition of much broader, and more ambitious, potential of cognitive radios.

For example, in recent years, cognitive radios have been proposed for e-health, telemedicine, and Wireless Medical Telemetry Services (WMTS) [38, 39]; for emergency and first-responder communications [41–43]; and for jamming and anti-jamming systems [45, 47, 50]. These applications are not merely motivated by improving spectrum utilization. Instead, cognitive communication is used to achieve some of the key performance objectives and to overcome certain inherent challenges. These include system and regulatory constraints, reliability, security, robustness, and energy and spectral efficiency. For instance, according to FCC regulations, WMTS communications are allowed in three noncontiguous spectrum bands: TV channel 37 (608–614 MHz), lower L band (1395–1400 MHz), and upper L band (1427–1432 ...