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Abstract: At present multiband wireless devices are able to select their working frequency only to a limited extent because of the strict, current spectrum regulation. Dynamic spectrum access is a promising approach that might solve this inefficiency. The authors focus on spectrum sensing, one of the main tasks involved. First, three strategies are compared to efficiently sense the current spectrum based on the spectrum occupancy information statistics. In contrast to the simulation-based studies, the authors evaluate the performance of those strategies on real spectrum occupancy data gathered during an extensive measurement campaign. The authors show that the usage of historical information considerably improves the spectrum sensing process and also that the modelling of the periodic behaviour of the licensed signals leads to negligible performance enhancements because only very few periods shorter than several minutes can be found within 20 MHz-6 GHz. Secondly, the authors unveil the fundamental tradeoff between the required bandwidth for the transmission and the total bandwidth that has to be sensed in order to guarantee that the required bandwidth is available. All the results are provided in terms of outage probability that can be viewed as an approximation of the packet loss rate.
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1 Introduction
The flexibility and adaptiveness of wireless devices has been significantly improved during the recent years. Meanwhile the complexity of involved system increased considerably. In the cognitive radio paradigm [1, 2], devices are aware of their surroundings and capable of learning in order to manage this system complexity. The working frequency and the used bandwidth are two of the main working parameters that cognitive radios could dynamically optimise in order to adapt to the environment variations [3]. These proposals have also been motivated by several measurement results [4 - 8] that showed the inefficiency of the current mostly static spectrum regulations. All these measurement campaigns have found significant amount of unused spectrum (e.g. 80% in global system for mobile communications (GSM) bands in the case of normal usage [8]). Such vacancies were found despite the fact that most of the spectrums are licensed. This has led many authors to argue that the current spectrum regulation is highly suboptimal. Advanced techniques for dynamic spectrum access (DSA) attempt to exploit the free spectrum...