ABSTRACT
Recently, there has been extensive research on cognitive radio (CR) which bridges the enormous gulf in time and space between the regulation and the potential spectrum efficiency ( [1-3] and the references therein). One of the critical challenges is how to realize the coexistence of primary users (PUs) and cognitive users (CUs) accessing the same part of the authorized spectrum. The PUs have priority in accessing the frequency bands while the CUs
Fundamentals,
opportunistically transmit when the spectrum is idle, as illustrated in Figure 5.1. To avoid colliding with the licensed network, the CUs must sense before transmission to determine whether there are PUs over the selected channel. However, the PUs’ stochastic behavior patterns challenge the selection process.
