1. School of Communication and Information Engineering, Chongqing University of Posts and Telecommunications, Chongqing, China
2. Aerospace New Generation Communications Company Ltd., Palo Alto, CA, USA
3. Science and Technology on Security Communication Laboratory, Institute of Southwestern Communication, Chengdu, China
4. College of Computer Science, Chongqing University, Chongqing, China
5. Department of Electronic and Information Engineering, The Hong Kong Polytechnic University, Hong Kong, China