[1] Univ Aberdeen, Dept Comp Sci, Aberdeen AB24 3FX, Scotland
[2] Vanderbilt Univ, Dept Elect Engn & Comp Sci, 221 Kirkland Hall, Nashville, TN 37235 USA
[3] Univ Victoria, Dept Elect & Comp Engn, Victoria, BC V8P 5C2, Canada
[4] Shanghai Jiao Tong Univ, Dept Automat, Shanghai 200240, Peoples R China