1. Ph.D. Student, School of Aeronautics and Astronautics, Shanghai Jiao Tong Univ., Shanghai 200240, PR China.
2. Professor, General Dept. of Beijing Institute of Tracking and Telecommunications Technology, Beijing Institute of Orbiting and Telecommunications Technology, Beijing 100094, PR China.
3. Professor, School of Aeronautics and Astronautics, Shanghai Jiao Tong Univ., Shanghai 200240, PR China.
4. Professor, School of Electronic Information and Electrical Engineering, Shanghai Jiao Tong Univ., Shanghai 200240, PR China (corresponding author).