[1] Univ Newcastle, Fac Engn & Built Environm, Sch Elect Engn & Comp Sci, Callaghan, NSW 2308, Australia
[2] Ericsson Australia Pty Ltd, Tower B 112-118 Talavera Rd, N Ryde, NSW 2113, Australia
[3] Univ West Bohemia, Dept Math, Plzen, Czech Republic
[4] Kings Coll London, Dept Comp Sci, London WC2R 2LS, England