A unifying view on energy-efficiency metrics in cognitive radio channels

The objective of this paper is to provide a unifying framework of the most popular energy-efficiency metrics proposed in the wireless communications literature. The target application is a cognitive radio system composed of a secondary user whose goal is to transmit in an optimal energy-efficient manner over several available bands under the interference constraints imposed by the presence of the primary network. It turns out that, the optimal allocation policies maximizing these energy-efficiency metrics can be interpreted as Pareto-optimal points lying on the optimal tradeoff curve between the rate maximization and power minimization bi-criteria joint problem. Using this unifying framework, we provide several interesting parallels and differences between these metrics and the implications w.r.t. the optimal tradeoffs between achievable rates and consumed power.