1. Department of Electrical and Electronic Engineering, Imperial College London, London, UK. E-mail: m.cattafi@imperial.ac.uk
2. Department de Telecomunicació i Enginyeria de Sistemes, Universitat Autònoma de Barcelona, Cerdanyola del Vallès, Spain. E-mail: RHerrero.Math@gmail.com
3. EnDIF, Università di Ferrara, Ferrara, Italy. E-mails: marco.gavanelli@unife.it, maddalena.nonato@unife.it
4. Dipartimento di Elettronica e Informazione, Politecnico di Milano, Milano, Italy. E-mail: malucell@elet.polimi.it