1. Department of Mathematical and Computer Sciences, Physical Sciences and Earth Sciences, University of Messina, Viale F. Stagno d'Alcontres 31, 98166 Messina, Italy
2. Department of Engineering, Polo Scientifico Didattico di Terni, University of Perugia, Terni, TR I-50100, Italy
3. Department of Computer Science, Modelling, Electronics and System Science, University of Calabria, via P. Bucci 41C, I-87036 Rende (CS), Italy
4. Department of Engineering, University of Messina, c.da di Dio, I-98166 Messina, Italy
5. Department of Electrical and Information Engineering, Politecnico di Bari, via E. Orabona 4, I-70125 Bari, Italy