A vehicle-based measurement framework for enhancing whitespace spectrum databases

The present TV whitespace networks rely on spectrum occupancy databases to determine their operating channels. In this paper, we show that such databases cause non-negligible wastage of whitespace spectrum. We also report that whitespace channels can have very different quality due to interference from secondary devices and the leakage from TV broadcasts. Such disparity in channel quality is not captured by existing databases. We propose the use of spectrum measurements to overcome the above limitations of databases. In particular, we describe a system called V-Scope that leverages spectrum sensors on public vehicles to collect and report measurements from the road. These measurements are used as "anchor points" to construct various models to better determine whitespace spectrum, estimate its channel quality, and validate locations of primary and secondary devices. We have deployed our system on a single metro bus traveling across a mid-sized US city. Based on measurements collected at above 1 million locations over 120 square-km area, we find that a commercial database causes under-utilization of certain whitespace channels over a large area (up to 71% measured locations). Our system can reclaim this spectrum wastage at up to 59% locations, correctly selecting all the suitable whitespace channels at 72 -- 83% locations, and achieving a localization accuracy between 16 -- 27m.