Advances in opportunistic radio technologies for TVWS
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RESEARCH
Open Access
Advances in opportunistic radio technologies for TVWS Dominique Noguet*, Matthieu Gautier and Vincent Berg
Abstract Cognitive radio has been an active research area in wireless communications over the past 10 years. TV Digital Switch Over resulted in new regulatory regimes, which offer the first large-scale opportunity for cognitive radio and networks. This article considers the most recent regulatory rules for TV White Space opportunistic usage, and proposes technologies to operate in these bands. It addresses techniques to assess channel vacancy by the cognitive radio, focusing on the two incumbent systems of the TV bands, namely TV stations and wireless microphones. Spectrum-sensing performance is discussed under TV White Space regulation parameters. Then, modulation schemes for the opportunistic radio are discussed, showing the limitations of classical multi-carrier techniques and the advantages of filter bank modulations. In particular, the low adjacent band leakage of filter bank is addressed, and its benefit for spectrum pooling is stressed as a means to offer broadband access through channel aggregation. 1 Introduction Cognitive radio (CR) has been a major research topic in the radio communication community since it was introduced by Mitola in the early 2000s [1]. Cognitive Radio capitalizes on the flexible radio concept by setting the configuration of a flexible radio according to sensing and decision-making capabilities. Unfortunately, largescale deployment of CR in civil telecommunication systems was somewhat limited. This is mainly because its full benefits would require disruptive regulation rules, where spectrum resources would be allocated according to actual needs at a specific location in space and time, rather than ruled by fixed frequency assignments [2]. Therefore, first experimental over-the-air testbeds were restricted to the ISM bands [3-5] and/or to the research community [6,7]. In some countries, the so-called digital switch over (DSO) in TV bands has recently resulted in relaxed regulatory regimes, where unlicensed spectrum use is allowed, provided that non-harmful interference to incumbent systems is guaranteed. This move was first initiated in the USA, where the first proposed rules for the “Unlicensed Operation in the TV Broadcast Bands” were published as early as 2004 [8], with the final set of * Correspondence: [email protected] CEA-LETI MINATEC, 17 rue des Martyrs, 38054 Grenoble Cedex 9, France
rules in 2009 [9] and an additional notice in 2011 [10]. A similar trend is currently under way in other countries: for example, in the UK [11], Europe [12], and Australia [13]. As a consequence, the unused TV spectrum, referred to as TV White Space (TVWS), has become one of the very first portions of the spectrum where the concepts of CR meet regulatory and actual deploymentdriven requirement figures. Standardization actions to exploit the TVWS have been carried out within IEEE802 groups, first in IEEE802.22 [14], and more recently in IEEE802.11af [15]. Both st
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