1. Institute of Control and Computation Engineering, University of Zielona Góra, ul. Podgórna 50, 65-246 Zielona Góra, Polande-mail: b.cichy@issi.uz.zgora.pl
2. Institute of Control and Computation Engineering, University of Zielona Góra, ul. Podgórna 50, 65-246 Zielona Góra, Polande-mail: k.galkowski@issi.uz.zgora.pl
3. Electronics and Computer Science, University of Southampton, Southampton SO17 1BJ, UKe-mail: etar@ecs.soton.ac.uk