[1] Murdoch Univ, Sch Informat Technol, Perth, WA 6150, Australia
[2] Australian Natl Univ, Dept Comp Sci, Canberra, ACT 0200, Australia
[3] Budapest Univ Technol & Econ, Dept Telecommun & Media Informat, H-1117 Budapest, Hungary
[4] Szechenyi Istvan Univ, Mech & Elect Engn, Inst Informat Technol, Gyor, Hungary