12.1 Introduction

Cognitive radio, which is a recent concept introduced by Mitola [1], has been attracting significant interest and has the potential of shaping the future of wireless communication systems. The basic idea of the concept can be stated as employing smart wireless devices that are furnished with awareness, sensing, learning, and adaptation capabilities in order to utilize the available radio resources as efficiently as possible.

Since the concept of cognitive radio is still at the stage of being developed, there is no consensus on what kind of wireless technologies to employ for realizing it. There are a number of requirements a wireless system has to satisfy in order to be considered a suitable candidate for cognitive radio. These requirements include causing no interference to licensed systems, having an adjustable pulse shape, bandwidth, and transmit power, supporting various throughputs, providing adaptive multiple access, and ensuring the security of information. When the wireless systems that are potential candidates for cognitive radio are considered, Ultra Wideband (UWB) seems to be one of the tempting choices because it has an inherent potential to fulfill some of the key cognitive radio requirements. Therefore, the focus of this chapter will be on UWB and its suitability for cognitive radio. However, it is worth to stress that a cognitive radio might have the ability to synthesize and...