1. School of Information and Communication Engineering, Beijing University of Posts and Telecommunication, Beijing, China
2. Beijing Key Laboratory of Network System Architecture and Convergence, Beijing University of Posts and Telecommunications, Beijing, China
3. Beijing Laboratory of Advanced Information Networks, Beijing University of Posts and Telecommunications, Beijing, China
4. Beijing Engineering and Technology Research Center for Convergence Networks and Ubiquitous Services, University of Science and Technology Beijing, Beijing, China