In practical unlicensed communications in TV band, radio devices have to identify, at first, the transmission opportunities, that\nis, the portion of the spectrum licensed for broadcasting services unoccupied in a certain region at certain time, that is, the socalled\nTV white space. In this paper the outcome of field measurements in the UHF TV band (470ââ?¬â??860MHz) conducted in EU\nis presented. To obtain empirical values for the parameters upon which unlicensed radio devices are able to distinguish in a real\nscenario between empty and occupied TV channels, signal powermeasurements have been performed in Italy, Spain, and Romania\non rural, suburban, and urban sites, at different heights over the ground by using different analysis bandwidths.Theaimof this work\nis to provide a set of practical parameters upon which harmless unlicensed communication in the UHF TV white space is feasible.\nThe results have been analyzed with respect to the hidden node margin problem, spectrum sensing bandwidth, and occupancy\nthreshold.
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