1. Lanzhou Jiaotong University,School of Electronic and Information Engineering,Lanzhou,China,730070
2. Xi’an University of Posts & Telecommunications,Shaanxi Key Laboratory of Information Communication Network and Security,Xi’an,China,710121
3. Henan Polytechnic University,School of Physics and Electronic Information Engineering,Jiaozuo,China,454000
4. College of Computer Science and Engineering, Northwest Normal University,Lanzhou,China,730070, China