No abstract

For its simplicity and ease of implementation, Energy detection (ED) is attractive for spectrum sensing in cognitive radio (CR) systems. In ED, the energy captured is compared against a fixed detection threshold, which is estimated as a function of the noise power. Uncertainties caused by the imperfect knowledge of the noise power, referred to as noise uncertainty, leads to a reduced performance of the ED, particularly at low SNR levels. In this work, we introduce a novel approach that aims to overcome the SNR-wall problem of the ED caused by the noise uncertainty effects. This proposal relies on the cooperation of multiple receivers for adapting, at each sensing period, the detection threshold to the noise power present at the time of spectrum sensing process is occurring. The preliminary evaluation show that when the detection threshold is adapted to the current noise conditions, the ED observes a significant improvement on the probability of detection under the presence of noise uncertainty, compared to the non-adaptive threshold ED. Furthermore, with our proposal, the ED performs better than the well-known Eigenvalue-based Detection (EBD) and the Generalized Likelihood Ratio Test-based Detection (GLRD) for low to moderate sensing time and number of cooperating receivers.

No abstract

As sustainable development has emerged as a priority on the international agenda, increasing emphasis has been placed on “Life Cycle Sustainability Assessment (LCSA),” wherein environmental, economic, and social performance are comprehensively integrated. This study, as part of an LCSA approach, uses Social Life Cycle Assessment (S-LCA) to analyze the worker category social impact for concrete plants in South Korea. For the analysis, three types of concrete plant with different operating systems were selected and evaluated: Direct operation, operated by dedicated concrete manufacturers, and operated by cement suppliers. Eleven major social topics, which were mentioned in the international standards and international institutes, were selected as the subjects of evaluation; the social impacts were evaluated by applying the evaluative criteria for social topics presented in the Handbook for Product Social Life Cycle Assessment of PRé Sustainability. We determined that the highest social impact was found in concrete plants operated by cement suppliers (0.77), followed by plants operated by dedicated concrete manufacturers (0.50), and finally by plants with direct operations (0.09). These results can be applied by concrete plants to improve worker category areas in which they are lacking and by future researchers to evaluate the sustainable development of a variety of industries.