1. School of Software Engineering, South China University of Technology, Guangzhou, Guangdong, China
2. Department of Electrical and Computer Engineering, University of Nevada, Las Vegas, NV, USA
3. School of Computer Science and Electronic Engineering, University of Essex, Colchester, U.K.
4. Department of Microelectronics and Solid State Electronics, University of Electronic Science and Technology of China, Chenggdu, Sichuan, China