1. University of Žilina, Faculty of Electrical Engineering Department of Telecommunication and Multimedia Univerzitná 8215/1 010 26 Žilina Slovakia
2. National Research Council Canada Building M50, 1200 Montreal Road Ottawa Ontario Canada K1A 0R6
3. Departamento de Ingeniería de Comunicaciones ETSI Telecomunicación, Universidad de Málaga 29010 Málaga Spain