1. College of Electronic and Information Engineering, Southwest University, Chongqing, P.R. China
2. Science and Technology on Information Systems Engineering Laboratory, National University of Defense Technology, Changsha Hunan, P.R. China
3. School of Computer Science and Technology, Xidian University, Xi’an Shaanxi, P.R. China
4. College of Computer Science, Chongqing University, Chongqing, P.R. China