1. Unit of Industrial Autom., Industrial Systems Institute, Rion Patras, Greece
2. Unit of Digital Comm., Industrial Systems Institute, Rion Patras, Greece
3. GE Global Research, General Electric Co., Niskayuna, NY, USA
4. Dept. of Innov. Syst, University of Salerno, Fisciano, Italy
5. Dept. of Electrical Eng., University of Patras, Rion Patras, Greece