Two-stage spectrum detection in cognitive radio networks

Cognitive radios try to exploit “blank spaces” in the licensed band which are not being used by primary users at a particular place and time. In the absence of cooperation between the primary and the secondary networks, spectrum sensing enables secondary users to monitor a licensed band in order to find idle channels for opportunistic access. In this work, we propose a two-stage spectrum detection strategy that decreases the average channel search time by allowing the spectrum detector to focus on frequency channels which are more likely to be vacant. We show that the proposed detection strategy significantly outperforms the conventional single-stage strategy when the spectrum utilization is high.