Research Article On the Feasibility of Unlicensed Communications in the TV White Space: Field Measurements in the UHF Band M. Fadda, 1 V. Popescu, 2 M. Murroni, 3 P. Angueira, 4 and J. Morgade 4 1 Cagliari Research Unit, Italian University Consortium for Telecommunications, 09123 Cagliari, Italy 2 Department of Electronics & Computers, Transilvania University of Bras , ov, 500019 Bras , ov, Romania 3 Department of Electrical and Electronic Engineering, University of Cagliari, 09123 Cagliari, Italy 4 Department of Communications Engineering, UPV/EHU, Alda Urkijo S/N, 48013 Bilbao, Spain Correspondence should be addressed to V. Popescu; vlad.popescu@unitbv.ro Received 29 September 2014; Revised 20 January 2015; Accepted 3 February 2015 Academic Editor: Jintao Wang Copyright © 2015 M. Fadda et al. his is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. In practical unlicensed communications in TV band, radio devices have to identify, at irst, the transmission opportunities, that is, the portion of the spectrum licensed for broadcasting services unoccupied in a certain region at certain time, that is, the so- called TV white space. In this paper the outcome of ield measurements in the UHF TV band (470–860 MHz) conducted in EU is presented. To obtain empirical values for the parameters upon which unlicensed radio devices are able to distinguish in a real scenario between empty and occupied TV channels, signal power measurements have been performed in Italy, Spain, and Romania on rural, suburban, and urban sites, at diferent heights over the ground by using diferent analysis bandwidths. he aim of this work is to provide a set of practical parameters upon which harmless unlicensed communication in the UHF TV white space is feasible. he results have been analyzed with respect to the hidden node margin problem, spectrum sensing bandwidth, and occupancy threshold. 1. Introduction he current global move to switch from analogue to digital TV has opened up an opportunity for the reallocation of this valuable resource. In one way, spectrum bands once used for analogue TV broadcasting will be completely cleared, leaving a space for deploying new licensed wireless services, and, in another way, digital television technology geographically interleaves spectrum bands to avoid interference between neighboring stations, leaving a space for deploying new unlicensed wireless services. he complete transition from analogue to the digital TV was planned in Europe for 2012. Ater analogue switch- of the spectrum 790 MHz to 862 MHz (TV channels 61 to 69), the so-called digital dividend, was entirely cleared from broadcast. Within the remaining spectrum (470 MHz to 790 MHz) not all channels are occupied at each location, due to coverage limits in network planning. hese locally unused channels are called TV white space (TVWS) [1]. A number of the requirements to operate in TVWS are based on cognitive radio technology including location awareness and spectrum sensing [1]. hese new regulatory rules open up an opportunity to develop new wireless networks to utilize this spectrum. However, access to this new spectrum also comes with some technical challenges. here are a number of other requirements also that are intended to provide protection for the licensed services that operate in the TV bands. hese requirements impose technical challenges for the design of devices operating in TVWS spectrum. In the UHF band, the presence of digital terrestrial television (DTT) services [2] can be revealed by considering the information included in geolocation databases (GL-DBs) [3] if available, which provide for a certain location the list of the free DTT channels and the allowable maximum radiated power to transmit without harmful interference to DTT users [1, 4]. Studies [5, 6] conducted on compatibility problems in EU identiied the joint use of local inspection of the spectrum by means of opportunistic detection techniques (i.e., spectrum sensing) [7–9] which can be also cooperative [10], multiband Hindawi Publishing Corporation International Journal of Digital Multimedia Broadcasting Volume 2015, Article ID 319387, 8 pages http://dx.doi.org/10.1155/2015/319387