  A ubiquitous outdoor localization system that is easy to deploy and works
equally well for all mobile devices is highly-desirable. The GPS, despite its
high accuracy, cannot be reliably used for this purpose since it is not
available on low-end phones nor in areas with low satellite coverage. The
application of classical fingerprinting approaches, on the other hand, is
prohibited by excessive maintenance and deployment costs. In this paper, we
propose Crescendo, a cellular network-based outdoor localization system that
does not require calibration or infrastructure support. Crescendo builds on
techniques borrowed from computational geometry to estimate the user's
location. Specifically, given the network cells heard by the mobile device it
leverages the Voronoi diagram of the network sites to provide an initial
ambiguity area and incrementally reduces this area by leveraging pairwise site
comparisons and visible cell information. Evaluation of Crescendo in both an
urban and a rural area using real data shows median accuracies of 152m and
224m, respectively. This is an improvement over classical techniques by at
least 18% and 15%, respectively.
