[1] Sun Yat Sen Univ, Sch Elect & Commun Engn, Guangzhou 510275, Peoples R China
[2] Natl Univ Singapore, Dept Elect & Comp Engn, Singapore 117583, Singapore
[3] Univ Illinois, Coordinated Sci Lab, Urbana, IL 61801 USA
[4] Univ Illinois, Dept Elect & Comp Engn, Urbana, IL 61801 USA