1. School of Electrical and Computer Engineering, Aristotle University of Thessaloniki, Thessaloniki, Greece
2. Computer Science and Engineering Department, University of Ioannina, Ioannina, Greece
3. Institute of Computer Science, Foundation for Research and Technology Hellas (FORTH), Crete, Heraklion, Greece
4. Theoretical and Physical Chemistry Institute, National Hellenic Research Foundation, Athens, Greece
5. Department of System Integration and Interconnection Technologies, Fraunhofer IZM, Berlin, Germany
6. Truva Inc., Alpharetta, GA, USA