1. Electrical Engineering Division of DIAEE, University of Rome “Sapienza”, Rome, Italy
2. Instituto de Telecomunicações, Instituto Superior Técnico – Universidade de Lisboa, Lisboa, Portugal
3. Department of Information Engineering, Electronics and Telecommunications, University of Rome “Sapienza”, Rome, Italy
4. Electrical Engineering Department, University Federico II of Napoli, Napoli, Italy
5. Department of Electrical and Computer Engineering, University of Manitoba, Winnipeg, MB, Canada