ABSTRACT
The usage of radio spectrum resources and the regulation of radio emissions are coordinated by national regulatory bodies such as the Federal Communications Commission (FCC). The FCC assigns spectrum to licensed users, also known as primary users (PUs), on a long-term basis for large geographical regions. However, a large portion of the assigned spectrum remains underutilized as illustrated in Figure 1.1. The inefficient usage of the limited spectrum necessitates the development of dynamic spectrum access techniques [1], where users who have no spectrum licenses, also known as secondary users, are allowed to use the temporarily unused licensed spectrum. In recent years, the FCC has been considering more flexible and comprehensive uses of the available spectrum through the use of cognitive radio (CR) technology [2].
