1. State Key Laboratory of Rail Traffic Control and Safety, Beijing Jiaotong University, Beijing, China
2. School of Automation and Electrical Engineering, University of Science and Technology Beijing, Beijing, China
3. School of Marine Science and Technology, Northwestern Polytechnical University, Xi'an, China
4. State Key Laboratory of Rail Traffic Control and Safety, the Key Laboratory of Railway Industry of Broadband Mobile Information Communications, and the Beijing Engineering Research Center of High-speed Railway Broadband Mobile Communications, Beijing Jiaotong University, Beijing, China