1Department of Information Engineering, Electronics, and Telecommunications, SAPIENZA University of Rome, Via Eudossiana 18, 00184 Rome, Italy
2Istituto Nazionale di Geofisica e Vulcanologia, Via di Vigna Murata 605, 00143 Rome, Italy
3Department of Computer Science, Systems and Production, Tor Vergata University of Rome, Via del Politecnico 1, 00133 Rome, Italy