1. school of Electronic Engineering, Beijing University of Posts and Telecommunications, Beijing, China
2. China Satellite Network Application Co., Ltd, Beijing, China
3. Department of Automation, Tsinghua University, Beijing, China
4. National Mobile Communications Research Laboratory, Southeast University, Nanjing, China
5. Ministry of Education, Key Laboratory of Universal Wireless Communications, Beijing University of Posts and Telecommunications, Beijing, China
6. State Key Laboratory of Networking and Switching Technology, Beijing, China