I. Introduction
Proliferation of wireless devices and services, the need for higher data rates, and policy of fixed spectrum allocation have resulted in shortage of frequency resources for communication. This problem can be alleviated by using cognitive radios capable of dynamic spectrum access so that secondary users (SUs) can utilize resources temporarily unused by a primary user (PU) [1], [2]. However, this secondary access of the spectrum is on the condition that the interference caused to the PUs is strictly controlled and managed. Therefore, sensing, i.e., the process of gathering awareness about the surrounding radio environment, is essential for cognitive radios [2]– [4]. In addition to identifying idle spectrum and enabling cognitive communication, sensing can be also used to manage interference in wireless networks and to improve the spatial–temporal resolution and accuracy of the spectrum allocation databases.