1. School of Communications and Information Engineering, Chongqing University of Posts and Telecommunications, Chongqing, China
2. School of Electrical Engineering and the Computer Science Department, University of California at Merced, Merced, CA, USA
3. School of Mathematics and Statistics, Xi’an Jiaotong University, Shaanxi, Xi’an, China
4. School of Computer Science and Technology, Harbin Institute of Technology, Heilongjiang, Harbin, China