1. National Engineering Laboratory for Wireless Security; Xi'an University of Posts and Telecommunications; Xi'an China
2. State Key Laboratory of Integrated Services Networks; Xidian University; Xi'an China
3. State Key Laboratory of Information Security; Institute of Information Engineering, Chinese Academy of Sciences; Beijing China
4. School of Electrical and Electronics Engineering; Nanyang Technological University; Singapore
5. Department of Electrical and Computer Engineering; University of Waterloo; Waterloo ON Canada