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Energy efficient and fast yet reliable spectrum sensing in cognitive radio networks (CRNs) is an important issue and is often met through the involvement of (optimal) multiple sensing nodes in collaboration known as cooperative spectrum sensing (CSS). However, due to severe fading, sometimes transmission of sensing samples over some reporting channels (R-channels) consume much energy but contribute very little on global sensing decision. To address the problem, this work explores the scope of using an optimal checkpoint to stop further transmission of sensing samples over the deeply faded R-channels. First an energy minimization problem under the constraints of detection and false alarm probabilities is developed in an amplify forward relay assisted CSS system in terms of optimal sample checkpoint, the number of essential sensing/relay nodes and relay power gain. The problem is further extended in presence of primary user emulation attack (PUEA). Simulation results show that a performance gain ∼77.17% and ∼71.25% in energy consumption can be achieved for the proposed approach as compared to the existing two works at P d = 0.9 and P f = 0.05 . [ABSTRACT FROM AUTHOR]

Abstract: From time-to-time, experts endeavor to estimate the amount of energy lost due to friction and wear. According to one such estimate, over 4.22×1018 J of energy were lost in the United States in 1978 alone – enough to supply New York city for the entire year. A major factor in limiting our energy efficiency is energy loss through friction in tribo-elements is . In recognition of this, there have been significant efforts made during the past decades towards increasing the efficiency of bearing operations. The major influencing aspects of hydrodynamic lubrication are the structure of the lubricant film, the properties of the bearing surfaces, and the properties of the lubricant. Major past approaches for seeking efficiency improvement focused on the latter two of these aspects and concerned surface modification techniques and modification of lubricant properties. Here we advocate the third approach, modification of the structure of the lubricant film; this approach leads to what we call composite-film bearings (CFB). Composite-film bearings rely on a double layer, composite lubricant film to separate the load-bearing surfaces. We show in this paper that, while maintaining safe film dimensions, composite-film bearings perform with considerably lower frictional losses then do traditional bearings. In designing the CFB scheme, we rely on nature to seek out and maintain a configuration that minimizes viscous dissipation . This will be achieved in our case by the localization of deformation, and thus of viscous dissipation, to the low-viscosity component of the film. The CFB construction appears to be particularly suitable to power generating equipment. The journal bearings of these large rotating apparatus dissipate considerable energy ; the CFB has the potential to cut these losses. [ABSTRACT FROM AUTHOR]

The article reports that according to a study of industrial research firm Bell Telephone Laboratories Inc. mixing the macro and small radio sizes of existing ultra-broadband mobile networks can result in 50 percent energy savings. It states the discovery is a part of the company's research project called IntelliSpektrum and mentions that the findings also inferred advantages of large numbers of small cells over those of macro base stations.