Distributed medium access control for energy efficient transmission in cognitive radios

In the last few years the issue of energy-efficient network design has gained increasingly more importance, both in academia and in industry. Information and communication technologies (ICT) represent about 2% of the entire world's energy consumption, and the situation is likely to reach a point where ICT equipments in large cities will require more energy than is actually available. In this paper we develop and investigate methods for energy efficiency optimization for wireless networks with cognitive units. We show that the problem can be solved without explicit message passing using a modified distributed auction algorithm. Then we introduce a fast converging algorithm that approximates the solution to the maximal energy efficiency problem. We state conditions under which the fast algorithm is asymptotically optimal in terms of the number of users. Finally, we provide simulated examples of the methods developed in this article.