On Metrics and Models for Energy-Efficient Design of Wireless Access Networks

The energy efficiency of wireless access networks has attracted significant interest, due to escalating energy cost and environmental concerns. How energy efficiency should be measured is, however, still disputed in the literature. In this letter, we discuss the impact of performance metrics and energy consumption models in network dimensioning. We argue that, using a popular metric, the number of bits/Joule may give misleading results, unless the capacity and coverage requirements of the system are carefully defined. We also claim that the energy consumption in the backhaul and the idle power of the base stations have to be taken into account. To support our claims, we demonstrate in a simple example how misleading results can be obtained by using flawed performance metrics.