1. Department of Electrical and Computer Engineering, Pole II, Institute of Systems and Robotics (ISR-UC), University of Coimbra, Coimbra, Portugal
2. Department of Electrical and Computer Engineering, Pole II, Institute for Systems Engineering and Computers (INESC), University of Coimbra, Coimbra, Portugal
3. Department of Electrical and Computer Engineering, Pole II, Instituto de Telecomunicações (IT-UC), University of Coimbra, Coimbra, Portugal