Energy efficiency is a subtle concept: fundamental trade-offs for cognitive radio networks

This article discusses the implications of facilitating higher energy efficiency in cognitive radio networks from the perspective of fundamental trade-offs (i.e, what needs to be sacrificed to be energy-efficient). These trade-offs are identified as QoS, fairness, PU interference, network architecture, and security, which are also essential network design dimensions. We analyze these dimensions and their interactions focusing on energy efficiency. Furthermore, future research directions related to the integration of CRN with other networking paradigms and energy efficiency are introduced and discussed.