1. Chongqing Key Laboratory of Signal and Information Processing, School of Communication and Information Engineering, Chongqing University of Posts and Telecommunications, Chongqing, China
2. Electrical and Computer Engineering Department, The University of New Mexico, Albuquerque, NM, USA
3. School of Information Science and Engineering, Southeast University, Nanjing, China
4. College of Computer Science, Chongqing University, Chongqing, China
5. Electrical and Computer Engineering Department, University of California at Davis, Davis, CA, USA