1. School of Computer and Information Engineering, Henan Normal University, Xinxiang, China
2. School of Computer Science and Technology, Engineering Research Center of Network Management Technology for High-Speed Railway of Ministry of Education, Beijing Jiaotong University, Beijing, China
3. Beijing National Research Center for Information Science and Technology, Tsinghua University, Beijing, China
4. School of Electrical Engineering and Telecommunications, UNSW Sydney, Sydney, NSW, Australia
5. Department of Electrical and Computer Engineering, Hong Kong University of Science and Technology (HKUST), Hong Kong, Hong Kong