Are cognitive radios energy efficient? A study of the Wireless LAN scenario

Cognitive radios have been proposed in recent years to make more efficient use of the wireless spectrum and alleviate congestion on widely used frequency bands. A key aspect of these radios is the `cognition´ gained through a spectrum scanning process. The benefits of this cognition is apparent and well studied in terms of better performance of communication. The benefits in terms of reduced energy consumption, however, due to easier channel access and less contention have not been quantified in prior work. On the other hand, spectrum scanning to gain cognition is a power-intensive process and the costs incurred in terms of lost energy need to be accounted for. Thus, it is not clear whether a cognitive radio would be more energy efficient than a conventional radio, and if so, under what circumstances. This focus on energy consumption is particularly important when considering portable communication devices that are energy constrained. This work takes a first step in this direction by exploring whether a cognitive radio can save energy over a conventional radio in the ad hoc wireless LAN scenario. The interplay between different important parameters to this problem is analyzed and their impact on energy consumption studied.