1. School of Information Engineering, Xijing University, Xi’an 710123 China
2. College of Computer Science and Technology, Jilin University, Changchun 130012 China
3. Yizhi School of Agriculture and Forestry, Xiangyang Polytechnic Institute, Xianyang 712000, China
4. School of Computer Science, Northwestern Polytechnical University, Xi’an 710072, China
5. College of Computer Science and Electronic Engineering, Hunan University, Changsha 410082, China
6. School of Telecommunications, Lanzhou University of Technology, Lanzhou 730000, China