Ann. Telecommun. (2012) 67:171–180 DOI 10.1007/s12243-012-0292-0 Cross-layer sensors for green cognitive radio Jacques Palicot Received: 28 June 2011 / Accepted: 27 January 2012 / Published online: 13 March 2012 © Institut Télécom and Springer-Verlag 2012 Abstract Green cognitive radio is a cognitive radio (CR) that is aware of sustainable development issues and deals with an additional constraint as regards the decision-making function of the cognitive cycle. In this paper, it is explained how the sensors distributed throughout the different layers of our CR model could help on taking the best decision in order to best con- tribute to sustainable development. Keywords Green radio · Green communications · Cognitive · Software radio · Electromagnetic pollution · Consumption · Sustainable development 1 Introduction Not so many years ago, sustainable development was only the preoccupation of ecological groups. How- ever, sustainable development has become an issue and an aspiration of our civilization since the Resolu- tion 42/187 of the United Nations General Assembly in December 1987. The Brundtland Commission [1] defined sustainable development as the development that “meets the needs of the present without com- promising the ability of future generations to meet their own needs”. Then, several United Nations con- ferences (from Rio de Janeiro-1992, to Durban-2011) have confirmed this important issue. One of the most obvious aspects of sustainable development is climate change associated partly with CO 2 emission. The first J. Palicot (B ) SUPELEC/IETR, 35576 Cesson-Sévigné, France e-mail: jacques.palicot@supelec.fr related paper, which described green radio as a way of decreasing electromagnetic pollution (mainly from the human exposure point of view) with credits to the cognitive radio concept, has been presented several years ago in a Union of Radio Science (URSI) general assembly [2]. But, at that time, this type of preoccupa- tion was not in the trend. Currently, 3% of the worldwide energy is consumed by the information and communication technology (ICT) infrastructure which causes about 2% of the worldwide CO 2 emissions (comparable to the world- wide CO 2 emissions due to airplanes). These values of carbon footprint are very impressive. They have been confirmed by a lot of studies and reported in many conferences and workshops such as the “Next Gener- ation Wireless Green Networks Workshop”, held in SUPELEC in November 2009 [3]. One should deal with twofold aims in order to at- tempt solving these problems: • decrease the ICT footprint itself and • use ICT so as to decrease the “human being” activ- ities’ footprint. In this paper we deal with the first point from the mobile networks point of view. As it is said in the CFP of this Special Issue that “It is time to drastically reduce the power consumption of mobile networks by either decreasing the share of energy consumption of the radio access networks locally or globally from an end to end network perspective”, we strongly believe and we explain in this paper that cognitive radio has an important role to play in the green radio field. Since CR performs a local adaptation of needs and resources, it is used to decrease locally energy consumption. In fact, whatever the equipment of the mobile network is,