1. Department of Mathematics, University of Patras, Patras, 26500, Greece
2. Department of Electrical and Computer Engineering, University of Patras, Patras, 26500, Greece
3. Department of Mathematics, University of Patras, Educational Software Development Laboratory, Patras, 26500, Greece
4. Department of Electrical and Computer Engineering, University of Patras, Wire Communications Laboratory, Patras, 26500, Greece