[1] Institute of Computer Science and Telecommunications, Faculty of Engineering, University of Catania, Viale A. Doria 6, 95125 Catania, Italy
[2] INFN, Section of Catania, Corso Italia 57, 95129 Catania, Italy
[3] Department of Physics, University of Messina, Contrada Papardo, Salita Sperone 31, 98166 Messina, Italy