1. College of Civil Aviation, Nanjing University of Aeronautics and Astronautics, Nanjing 211106, China
2. State Key Laboratory of Air Traffic Management System and Technology, Nanjing 210007, China
3. Jiangsu Sub-bureau of East China Regional Air Traffic Management Bureau, Nanjing 211100, China
4. Department of Aviation and Technology, College of Engineering, San Jose State University, San Jose, CA 95192-0061, USA