Tradeoff between energy consumption and detection capabilities in collaborative cognitive wireless networks

In this paper, we analyze a cognitive wireless scenario, where a primary wireless network (PWN) coexists with a cognitive (or secondary) wireless network (CWN). The PWN uses licensed spectrum and the nodes of the CWN cooperate to detect idle subchannels (not used by the PWN's nodes), possibly taking into account the knowledge of their positions'. On the basis of this scenario, we present a simple, yet effective, framework to analyze the tradeoff between the CWN detection capabilities, i.e., the probability of detecting an unused lincensed subchannel, and the energy consumption needed to detect this subchannel. To this end, we introduce a novel performance indicator, denoted as detection energy efficiency. Our results show that there is an optimal working point, i.e., an optimal number of collaborating CWN nodes that allows to achieve the highest detection energy efficiency.