[1] Woods Hole Oceanog Inst, Dept Appl Ocean Phys & Engn, Woods Hole, MA 02543 USA
[2] Chinese Univ Hong Kong, Dept Informat Technol, Hong Kong, Hong Kong, Peoples R China
[3] Heriot Watt Univ, Dept Elect Elect & Comp Engn, Edinburgh EH14 4AS, Midlothian, Scotland
[4] Heriot Watt Univ, Dept Elect Elect & Comp Engn, Edinburgh EH14 4AS, Midlothian, Scotland