1. Institute for Communications and Navigation; DLR- German Aerospace Center; Wessling 82234 Germany
2. DITEN - Department of Naval, Electrical, Electronic and Telecommunications Engineering; University of Genoa; Via Opera Pia 13 Genova 16145 Italy
3. Institute of Electronics, Computer and Telecommunication Engineering; National Research Council of Italy; Via De Marini 6 Genoa 16149 Italy