[1] Katholieke Univ Leuven, Dept Elect Engn, B-3001 Louvain, Belgium
[2] Acad Sinica, Inst Stat Sci, Taipei 11529, Taiwan
[3] Natl Res Council Italy, Ist Applicaz Calcolo M Picone Sez Bari, I-70126 Bari, Italy
[4] McGill Univ, Sch Comp Sci, Montreal, PQ H3A 2A7, Canada
[5] Kyiv Natl Taras Shevchenko Univ, UA-01033 Kiev, Ukraine