SenseLess: A Database-Driven White Spaces Network
IEEE Transactions on Mobile Computing
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The recently released TV whitespaces offer a promising land for wireless communications. The secondary users of TV whitespaces today rely on spectrum occupancy databases to determine vacant TV channels for unlicensed communications. However, the accuracy of these databases (that depend solely on propagation models as per guidelines of the FCC) may be low. In this paper, we propose V-Scope - a vehicular sensing framework aimed to collect wide-area spectrum measurements for evaluating the accuracy of these databases. A key design feature of V-Scope is to leverage spectrum sensors mounted on public vehicles for collecting and reporting measurements from the road (opportunistic wardriving). We have currently deployed a version of our system on a single public transit bus traveling across a mid-sized city in the US. Based on measurements collected at over 1 million locations across a 100 square-km area, we find that databases tend to over-predict the coverage of certain TV broadcasts, unnecessarily blocking the usage of whitespace spectrum in a large area (up to 42% measured locations). We further propose ways of leveraging these measurements to enhance existing propagation models in databases.