1. School of Information and Software Engineering, University of Electronic Science and Technology of China, Chengdu, China
2. Department of Electrical and Computer Engineering, National University of Singapore, Singapore, Singapore
3. School of Electronic Information and Electrical Engineering and the Key Laboratory of Pattern Recognition and Intelligent Information Processing of Sichuan, Chengdu University, Chengdu, China
4. School of Mathematical Science, University of Electronic Science and Technology of China, Chengdu, China