1. School of Electronic and Information Engineering, Beihang University, Beijing 100191, China; Key Laboratory of Advanced Technology of Near Space Information System, Ministry of Industry and Information Technology of China, Beijing 100191, China
2. Shanghai Key Laboratory of Satellite Network, Shanghai 201204, China
3. Shanghai Key Laboratory of Satellite Network, Shanghai 201204, China; Shanghai Satellite Network Research Institute Co., Ltd., Shanghai 201204, China