ABSTRACT
Energy efficiency (EE) is becoming a central research focus in communication in the current context of growing energy demand and increasing energy price [1, 2]. In the past, this area has already been thoroughly investigated but only through the prism of power-limited applications such as batterydriven systems [3], e.g. mobile terminals, underwater acoustic telemetry [4], or wireless ad-hoc and sensor networks [5,6]. Nowadays, this area is being revisited for unlimited power applications such as cellular networks [7, 8]. This shift of focus in the research agenda from power-limited to power-unlimited applications is mainly driven by two factors: environmental, i.e. reducing the carbon footprint of communication systems, and; commercial, i.e. reducing the ever-growing operational cost of network operators. And yet, the spectral efficiency (SE) remains a key metric for assessing the performance of communication systems. The SE, as a metric, indicates how efficiently a limited frequency spectrum is used but fails to provide any insight on how efficiently the energy is consumed. In a context of energy saving, the latter will become as important as the former and, therefore, it has to be included in the performance evaluation framework.
