ABSTRACT
It has been estimated that a reasonable amount of worldwide energy is consumed by the information and communications technology (ICT) industry. Arnold et al. [1] indicate that this value has reached 2% of the worldwide energy consumption. Moreover, as stated in Ref. [2], around 0.5% of the total energy is used for wireless communications (equivalent to 650 TWh), and most of which (around 90%) is consumed in the outdoor cellular network, mainly by the base stations (BSs). One can assume that this percentage contribution to the total energy consumption will increase along with the advent of 4G wireless technologies and in general with the continuous tendency to increase total data traffic in the current and future communication networks. This increase in data traffic requires an improvement in the utilization of available resources. In general, this problem can be solved in at least three ways, but each of them entails higher energy consumption. First, one can go closer to the Shannon capacity limit, which means more complex systems with more processing energy consumption. Second, in some cases, the transmit power can be increased, and third, the density of frequency reuse can be enhanced, which generally results in an increase in network entities. Thus, in order to lower energy consumption while satisfying future demands, work on green communication and networking is being undertaken by the ICT community. Various initiatives have been started in the last couple of years, emphasizing the need for energy-efficient communication and networking, both wired and wireless. Moreover, energy efficiency can also be supported by the international standardization bodies by proposing energy-efficient solutions in their recommendations and documents.
