Energy conservation and harvesting for green communications [Guest editorial]

Conventional communication technologies are targeted mainly at spectrum efficiency, but not energy efficiency and environmental friendliness. Recent efforts from both industry and academia have dedicated to reduce the energy consumption and carbon emissions of the information and communication technologies (ICTs). There are two ways to achieve this goal: one is to conserve energy through energy-aware operation optimizations, and the other is to harvest renewable energy from ambient energy resources, such as solar, wind, etc., to power communication nodes. However, both ways are facing challenges. For instance, energy conservation in most cases has to sacrifice the quality of service (QoS), and one must balance the energy efficiency and QoS requirements to achieve a good tradeoff between them. For energy harvesting, the randomness of energy generation hinders reliable communications, and limited battery capacity together with imperfect battery technology causes extra problems. In addition, spatial-temporal mismatch of energy arrivals and traffic demands should be addressed with innovative node placement and resource management schemes.