1. Department of Information Science, China University of Mining and Technology, Xuzhou, Jiangsu, China, (e-mail: jsywow@gmail.com)
2. Electrical and Computer Engineering, University of Alabama in Huntsville, Huntsville, Alabama, United States, 35899 (e-mail: jianqing.liu@uah.edu)
3. Department of Information Science, China University of Mining and Technology, Xuzhou, Jiangsu, China, (e-mail: yzhou@cumt.edu.cn)
4. Department of Electrical and Computer Engineering, University of Florida, Gainesville, Florida, United States, 32611 (e-mail: fang@ece.ufl.edu)