1. Key Laboratory of Electronic and Information Technology in Satellite Navigation, Ministry of Education, Beijing Institute of Technology, Beijing, China
2. Department of Computing, The Hong Kong Polytechnic University, Hung Hom, Hong Kong
3. Chongqing Innovation Center, Beijing Institute of Technology, Chongqing, China
4. Department of Electrical Engineering and Computer Science, The University of Tennessee at Knoxville, Knoxville, TN, USA