1. School of Electronic and Information Engineering, Beijing Jiaotong University, Beijing, China
2. Department of Computer Science, KTH Royal Institute of Technology, Kista, Sweden
3. Hunan International Scientific and Technological Cooperation Base of Intelligent Network and the Key Laboratory of Intelligent Computing and Information Processing of Ministry of Education, Xiangtan University, Hunan, China
4. State Key Laboratory of Rail Traffic Control and Safety and Frontiers Science Center for Smart High-Speed Railway System, Beijing Jiaotong University, Beijing, China