Department of Electrical and Computer Engineering, University of Nevada, 4505 Maryland Parkway, Box 454026, Las Vegas, NV 89154, USA Tel.: +1 702 895 2364/ fax: +1 702 895 4075.;Department of Electrical and Computer Engineering, University of Nevada, 4505 Maryland Parkway, Box 454026, Las Vegas, NV 89154, USA Tel.: +1 702 895 2364/ fax: +1 702 895 4075.;Department of Computer Science and Technology, Harbin Institute of Technology, #715 No. 92 West Da-Zhi Street, Harbin, Heilong Jiang 150001, P.R. China Tel.: +86 451 86417772.;Department of Computer Science, Nankai University, No. 94 Weijin Rd, Nankai District, Tianjin 300071, P.R. China. Tel.: +86 22 23503756.