behind this paper.

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WeFi, now acquired by TruConnect Technologies, is an Android application providing location-specific information on the speed, security, and reliability of nearby Wi-Fi networks. At the same time, it collected data on the activity of its users, including location, mobile phone activity, and available connectivity options. For our study we use three datasets, coming from the U.S. cities of Atlanta, Los Angeles, and San Francisco, characterized by the features summarized in [Tab. \[tab:datasets\]]{}.

[1]{}[|c|X|X|X|]{} & Atlanta & Los Angeles & San Francisco\
Time of collection & Oct. 2015 & Oct. 2015 & Mar. 2015\
Covered area \[km$^2$\] & $55\times 66$ & $46\times 73$ & $14\times 11$\
Total traffic \[TB\] & 9.34 & 35.61 & 9.18\
Number of records & 13 million & 81 million & 60 million\
Unique users & 9,203 & 64,386 & 14,018\
Unique cells & 12,615 & 36,09 & 14,728\

Datasets are organized in [*records*]{}, each containing: time and GPS location; anonymized user identifier; current operator and cell identifier; active application on the smartphone and amount of data it downloads. New records are generated every time any of the above changes (e.g., the user moves or switches apps), or a one-hour 