[1] Univ British Columbia, Dept Elect & Comp Engn, Vancouver, BC V6T 1Z4, Canada
[2] Simon Fraser Univ, Sch Comp Sci, Burnaby, BC V5A 1S6, Canada
[3] Natl Chiao Tung Univ, Dept Comp Sci, Hsinchu 300, Taiwan
[4] Acad Sinica, Inst Informat Sci, Taipei 115, Taiwan
[5] Natl Tsing Hua Univ, Dept Comp Sci, Hsinchu 300, Taiwan