1. Department of Electrical Engineering, Federal University of Rio Grande do Sul, 90035-190 Porto Alegre, RS, Brazil
2. Dipartimento di Elettronica, Informazione e Bioingegneria (DEIB), Politecnico di Milano, 20133 Milano, Italy
3. National Research Council of Italy (C.N.R.), Institute of Electronics, Computer and Telecommunication Engineering (IEIIT), 20133 Milano, Italy
4. Department of Automation Systems, Federal University of Santa Catarina, 88040-900 Florianopolis, SC, Brazil
5. Institute of Informatics, Federal University of Rio Grande do Sul, 91501-970 Porto Alegre, RS, Brazil