Special issue on green radio

Society has grown increasingly aware of the need to reduce CO2 emissions in order to mitigate consequential environmental effects. The primary contributors to CO2 emissions are electric power generation, transport, and manufacturing. Information and Communications Technology (ICT) at present contributes a non-negligible 3% of world-wide energy consumption, which in turn causes about 2% of the world-wide CO2 emissions. The dramatic growth in Internet traffics and the growing pervasive use of mobile and wireless technologies to support this are likely to increase CO2 emissions in the future unless greater energy efficiency can be achieved in networking technologies. Thus, thedevelopment of wireless networks that require lower energy consumption is desirable. In addition to this key driver of reducing CO2 emissions, the cost of energy has increased substantially and this is a significant proportion of the costs of any wireless access infrastructure company. These issues have resulted in an increased interest in “green radio” networks that reduce the energy requirements for wireless communications, and can thus contribute not only to goals for sustainable development, but also to the profitability of the telecommunication industry. Although green radio can be justified in the context of energy consumption as noted above, it also can be viewed in a wider sense, such as in the optimization of spectrum usage to reduce electromagnetic radiation levels in order to enable coexistence of multiple wireless systems (i.e., less interference) as well as to reduce human exposure to radiation, in the recycling and reuse of ICT equipment, and in many other related contexts. There are 17 papers in this special issue. It is difficult to classify these papers into distinct categories, as many of them deal with several aspects of green radio. Nevertheless, the classification proposed by Luis Suarez, Loutfi Nuaymi, and Jean-Marie Bonnin in their overview paper (see below) seems very appropriate for classifying these papers and, referring to Figure 1, we can make use of this classification as follows. In particular, this special issue has assembled papers